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Other titles Journal of developmental physiology, Developmental physiology
ISSN 0141-9846
OCLC 5152455
Material type Periodical
Document type Journal / Magazine / Newspaper

Publications in this journal

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    ABSTRACT: Effects of extracellular Ca2+ and inotropic agents on contractile force were examined in myocardial preparations from embryonic and hatched chicks. Measurement of contractile force was performed in an organ bath with whole hearts for the young embryo (5 to 6 days old) and with isolated strips from the right ventricles for the old embryos (16 to 18 days old), hatched chicks (within 24 hours after hatching) and 1 week old chicks. The extracellular Ca2+ concentration-contractile force curve was in a lower concentration range in young embryonic hearts when compared with older ones. 2 mM Ca2+ and 8 mM Ca2+ produced about 60% maximum contraction in preparations from young embryos and the older ages, respectively. The sensitivity to nicardipine and diltiazem was similar among all ages examined under 2 mM Ca2+. When the two drugs were applied to preparations from the older ages under 8 mM Ca2+, the sensitivity was lower than that of the young embryo under 2 mM Ca2+. Ryanodine produced a negative inotropic response at all ages but the effect was smaller in the young embryo when compared with those of older ages. Mn2+ produced a negative inotropic effect at all ages. In the older three ages, Mn2+ produced a late augmentation of the contractile force in addition to the initial negative inotropic response, while such augmentation was not observed in the young embryo. In conclusion, the chick myocardium was shown to undergo developmental changes in excitation-contraction mechanisms including increase in sarcoplasmic reticulum function during the embryonic period, and thus provides an interesting model for studies on excitation-contraction mechanisms.
    Journal of developmental physiology 07/1993; 19(6):235-40.
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    ABSTRACT: Norepinephrine (NE) content and turnover rate, and the activity of dopamine-beta-hydroxylase (DBH) were measured in the brown adipose tissue (BAT) of developing Zucker rats of the three genotypes: Fa/Fa and Fa/fa (with a lean phenotype) and fa/fa (phenotypically obese). As early as 15 days of age, namely at a pre-obese stage, BAT NE content and turnover rate are already reduced in fa/fa rats, just like they are at 50 days. The development of DBH activity is completely impaired in fa/fa rats. These results demonstrate that the reduction in sympathetic tone in BAT of fa/fa rats is already present before the onset of phenotypic obesity.
    Journal of developmental physiology 07/1993; 19(6):247-51.
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    ABSTRACT: The administration of 17-beta estradiol to human, and all the animals species tested, results in blood volume expansion. This effect has been postulated to be mediated through an increase in the circulating levels of aldosterone. We infused 17-beta estradiol (30 micrograms/kg/day) into 5 chronically-castrated ewes over a 3-week period, and determined the plasma concentrations of 17-beta estradiol, PRA, and aldosterone at weekly intervals. By the end of the third week, 17-beta estradiol plasma concentration had increased 150-fold, while PRA increased 2-fold; aldosterone decreased 40% from baseline values. Thus, during a period in which we have previously observed blood volume expansion, there was a dissociation between the levels of 17-beta estradiol and aldosterone. These findings question the theory that the estradiol-mediated blood volume increase observed during pregnancy is secondary to an increase in the circulating aldosterone levels.
    Journal of developmental physiology 06/1993; 19(5):213-5.
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    ABSTRACT: To investigate the role of thyroid hormone in the expression of the gene encoding the growth hormone receptor (GHR) and growth hormone binding protein (GHBP), fetal rats were made hypothyroid through the administration of the goitrogen methimazole to the mother. Euthyroidism was maintained in the mother by concurrent administration of L-thyroxine, which crosses the placenta poorly. Methimazole and L-thyroxine were continued in the mothers until weaning. After birth, groups of methimazole-treated or control pups were sacrificed immediately and at one, two, three, four, five, or six weeks after birth. In each group, weight was recorded, blood was obtained for measurement of T4, thyroid stimulating hormone (TSH), and growth hormone (GH), and liver tissue was obtained for quantitation of GHR and GHBP mRNA. The methimazole-treated pups were demonstrated to be hypothyroid, with markedly higher TSH and lower T4 concentrations, until weaning occurred between weeks three and four, after which they transiently became hyperthyroid at week five (T4 = 17 +/- 5 micrograms/dL vs. 6 +/- 0.5 micrograms/dL for controls) but returned to an euthyroid state at week six. In control pups the relative abundance of GHR and GHBP mRNA increased abruptly in week one, and increased three to four fold over the ensuing six weeks. Immediately after birth, the hypothyroid pups expressed significantly more GHR and GHBP mRNA than did the controls (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
    Journal of developmental physiology 06/1993; 19(6):241-6.
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    ABSTRACT: This study was designed to determine the effects of hypothyroidism during late fetal life in pigs on (1) the perinatal pattern of plasma levels of thyroxine (TT4), total 3,5,3'-triiodothyronine (TT3) and free T3 (FT3), and liver 5'-deiodinase activity, and (2) the early postnatal development of thermoregulation. Fetal hypothyroidism (test animals) was induced by feeding the sow a high glucosinolate rapeseed diet. Plasma levels of thyroid hormones, thyroid gland weights and liver 5'-deiodinase activity of control animals increased during late gestation (P < 0.01). The early postnatal period was characterized by a surge in thyroid hormone levels during the first 6 h (P < 0.05), followed by a transient decrease at 12 h and a second rise by 24 h after birth. This surge was much higher (P < 0.01) for TT3 than for TT4, but liver 5'-deiodinase activity did not change during the first 24 h of life. Fetal hypothyroidism was characterized by lower plasma levels of thyroid hormones (P < 0.05), and lower hepatic 5'-deiodinase activities (P < 0.01) than in control fetuses at 110 d of gestation. During the first 6 h of life, test pigs had lower levels of TT4 (P < 0.05) but exhibited a greater postnatal surge in TT3 and FT3 (P < 0.05) than did the controls. The minimal and summit metabolism of the control pigs increased markedly (P < 0.01) during the first 2 d of life, without any significant change in thermal body conductance, suggesting that this age-related improvement in thermoregulation was due to the development of the ability to produce heat.(ABSTRACT TRUNCATED AT 250 WORDS)
    Journal of developmental physiology 06/1993; 19(6):253-61.
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    ABSTRACT: Summary measures of heart rate variation describe those aspects of heart rate change that can be averaged over relatively long periods of time. We examined the postnatal maturation of a dynamic feature of cardiac rate--the dependency of each beat-to-beat change in cardiac interbeat interval on the previous beat-to-beat change. In each sleep-waking state, the number of delta RR (the difference between two successive R-R intervals) 4msec was determined as a percent of the total number of intervals (delta RR > 4ms/total delta RR), and each pair of successive interval differences was categorized based on the directions of the two changes (whether they reflected increases or decreases in cardiac intervals). Analysis of variance was used to identify alterations in the proportion of interval differences exceeding the minimum over ages and sleep-waking states, and to describe developments in the temporal patterns of cardiac interval changes. At all ages, infants showed fewer beat-to-beat interval changes during waking than during either sleep state. In all states, older infants showed significantly more beat-to-beat cardiac interval changes and a higher proportion of sustained changes (intervals increasing or decreasing consistently over several beats) than did young infants. Furthermore, infants 2 months and younger showed significantly more sustained increases than decreases in interbeat intervals, indicating gradual declines in heart rate and rapid increases, while older infants showed the opposite pattern.(ABSTRACT TRUNCATED AT 250 WORDS)
    Journal of developmental physiology 06/1993; 19(6):263-71.
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    ABSTRACT: During the critical period of receptor maturation within the first 5 days after birth female rats were treated with benzpyrene three times and their uterus estrogen receptor characteristic were examined in adulthood. Estrogen receptor density decreased significantly. There was no alteration in receptor affinity. Present experiment draws attention to the disadvantageous effect of aromatic hydrocarbons coming from the polluted air on steroid receptor development.
    Journal of developmental physiology 06/1993; 19(5):217-9.
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    ABSTRACT: Many pregnant women are exposed to low frequency sounds and vibrations while at work or play. How the fetus is affected by these physical stimuli is not clearly documented. We recorded behavioral state and intrauterine sound pressure levels in eight fetal sheep previously instrumented with electrocortical, electroocular and neck electromyographic leads, and with a miniature hydrophone. Data were collected before, during and after 30 min of abdominal vibration using a belt vibrator commonly used by humans in weight reduction programs. A sudden shift in behavioral state occurred at the onset of vibration. There was a decrease in non-rapid eye movement sleep (P < 0.02) and an increase in time during which the sleep state could not be determined (P < 0.03). A 63% increase in number of epochs spent in this indeterminate period was evident during vibration. During the post-stimulus period, percentage of time spent in rapid eye movement sleep decreased as compared to the pre-stimulus period (P < 0.04), and non-rapid eye movement sleep increased as compared to the stimulus period (P < 0.01). Vibration-induced intrauterine sound pressures ranged from 131-142 dB at the fundamental frequency of 19 Hz and were 20-40 dB lower at the overtones which appeared in the spectrum between 35-200 Hz. Results indicated that environmental vibration can disrupt fetal behavioral state, induce abnormal state changes, and alter distribution of sleep states.
    Journal of developmental physiology 06/1993; 19(6):227-34.
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    ABSTRACT: Behavioral state and cerebral glucose utilization were measured in six fetal sheep subjected to high intrauterine sound pressures created with a vibroacoustic stimulator pressed against the maternal abdomen. The signal consisted of a complex waveform that varied over time with a 50% duty cycle. An implanted hydrophone showed highest spectral levels between 3,000-16,000 Hz. The pulsed sound resulted in a significant loss of fetal rapid eye movement and non-rapid eye movement sleep. The stimulus also resulted in a disruption in the normally close relationship between these sleep states and cerebral glucose utilization rates in the brain as a whole and in its component parts.
    Journal of developmental physiology 05/1993; 19(4):171-7.
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    ABSTRACT: The aim of this study was to document arterial blood pressure wave forms at two sites along the arterial tree of the neonate: in the radial and posterior tibial arteries. Using a high-fidelity catheter tip-transducer system, peripheral arterial blood pressure wave forms in 26 critically newborn infants were studied. In 14 infants the radial artery and in 12 infants the posterior tibial artery was cannulated. Radial artery blood pressure waves resembled those of proximal aortic rather than those of the radial artery in adults. Quantitative analysis of the waves was performed to reassure this finding. Blood pressure waves obtained from posterior tibial artery resembled those of femoral artery rather than those of posterior tibial artery waves in adults. We conclude that radial and posterior tibial artery wave forms in neonates appear to have a central appearance. This phenomenon might be explained by the close proximity of the radial and posterior tibial artery to the central aorta and femoral artery respectively, due to the small and short limbs of the neonate. The finding allows an "easy central pressure look" at both ends of the neonatal aorta.
    Journal of developmental physiology 05/1993; 19(4):179-85.
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    ABSTRACT: The present studies were designed to characterize the developmental aspects of Na(+)-dependent phosphate transport, across the hepatocyte basolateral membranes of the suckling and weanling rats. A well validated technique of plasma membrane vesicles (BLMV) was utilized. Phosphate uptake was driven into an osmotically active intravesicular space as evident by a linear relationship between uptake and 1/osm with no binding component y = 0.04 x-0.03, r2 = 0.99 and y = 0.035x + 0.01, r2 = 0.95 in suckling and weanling BLMV's respectively. The presence of inwardly directed Na+ and pH gradient stimulated phosphate uptake in suckling and weanling BLMV's, however, uptake values under Na+ and pH gradients were greater in weanling rats compared to suckling rats. Kinetics of Na(+)-dependent phosphate uptake were 0.14 +/- 0.01 and 0.28 +/- 0.035 at pH 6.1 (P < 0.05) and 0.1 +/- 0.007 and 0.15 +/- 0.03 nmoles/mg protein/10s (P < 0.05) at pH 7.4 in suckling and weanling rats respectively. Km values were not significantly different. Na+ arsenate and phosphonoformonic acid inhibited Na(+)-dependent phosphate uptake, whereas ATP and P-MB (para-chlomercuribenzoic acid) did not effect Na(+)-dependent phosphate uptake. These studies demonstrate for the first time the presence of a specialized transport system for phosphate across the basolateral membranes of the rat liver during development. This transport system exhibit ontogenic characteristics in regard to its transport capacity.
    Journal of developmental physiology 05/1993; 19(5):197-201.
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    ABSTRACT: We hypothesized that exposure of neonatal swine to chronic alveolar hypoxia (CH) would cause increased PVR, blunt acute hypoxic vasoconstriction, and increase VA/Q mismatch. After exposure to either normobaric alveolar hypoxia (FIO2 = 0.10) or room air for 2 weeks, animals were anesthetized and ventilated first with room air and then with hypoxic gas (FIO2 = 0.12). PVR, and pressure-flow (P/Q) relations were measured between 15-100% of baseline cardiac output. VA/Q matching was measured by the multiple inert gas elimination technique. During room air breathing, the mean PVR and P/Q slope in the CH animals was significantly greater than in the control (C) animals. P/Q intercepts were similar and near the origin for both groups. The absolute PVR and P/Q slope were greater for CH compared to C animals during acute alveolar hypoxia. The fractional increase in PVR and P/Q slope in the response to acute hypoxia was similar for both groups. PaO2, intrapulmonary shunt, and SDQp (an index of VA/Q heterogeneity) were similar for both groups. We conclude that CH in neonatal swine causes pulmonary hypertension, but does not attenuate acute hypoxic pulmonary vasoconstriction, nor VA/Q matching.
    Journal of developmental physiology 05/1993; 19(4):157-63.
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    ABSTRACT: 5 alpha-reductase activity was measured in the developing rat urogenital tract using [3H] testosterone as substrate. At fetal day 22, the activity in the vagina (67 pmol/h per mg protein) was as high as in the differentiated prostate (41 pmol/h per mg protein). Both tissues are derived from the urogenital sinus. Although the activity of 5 alpha-reductase remained high in the prostate, the enzyme activity in the vagina declined steadily such that by postnatal day 20, the levels were not different from those expressed in urinary bladder which had low, baseline levels (approximately 10 pmol/h per mg protein) throughout the period examined. The uterus, which is derived from the embryonic mullerian duct, also expressed high levels (50-70 pmol/h per mg protein) of 5 alpha-reductase activity initially (before postnatal day 10). In contrast, the "Wolffian-derived" epididymis had levels of activity that were indistinguishable from the relatively low levels seen in the urinary bladder. In the ovary, neither 5 alpha-reductase nor aromatase activities were appreciable at fetal day 22 and at postnatal day 2. By postnatal day 5 both activities increased dramatically in ovaries. After postnatal day 10, aromatase activity declined in ovaries but 5 alpha-reductase remained elevated. These observations suggest (1) that major remodeling of the tissues derived from the urogenital sinus takes place even after differentiation and (2) that 5 alpha-reductase may regulate ovarian estrogen levels at the time of primary folliculogenesis.
    Journal of developmental physiology 05/1993; 19(4):187-91.
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    ABSTRACT: Lungs from near-term fetal guinea pigs were supported in vitro for 3 h; lung liquid production rates were measured by a dye dilution technique. Seventy preparations were used to study the effects of arginine vasopressin (AVP) placed in the outer saline for the middle hour, at concentrations reported at birth [fetuses 61 +/- 2 days of gestation; 94.7 +/- 16.2 g (SD) body weight]. At 1200 microU/ml, AVP arrested fluid production (rates, successive hours, 3.03 +/- 0.60, 0.50 +/- 0.14 and 0.02 +/- 0.08 ml/kg body weight per h; falls significant, P < 0.01-0.0005). At 600, 300 and 100 microU/ml there were significant but smaller reductions. Reabsorptions were seen in 8 preparations given 600-1200 microU/ml, AVP. Preparations given 10 microU/ml AVP, AVP carrier or control saline showed no significant change. The responses (% reductions during treatment), were linearly related to the log concentration of AVP (r = 0.99); theoretical threshold, 8 microU/ml). Increasing treatment to 2h did not increase final responses. Preparations from 5 fetuses > 120 g body weight showed significantly greater responses (P < 0.025) [fetuses 64 +/- 2 days of gestation; 135.1 +/- 18.6 g (SD) body weight]. 10(-6) M amiloride abolished responses to AVP [fetuses 62 +/- 1 days of gestation; 93.4 +/- 18.5 g (SD) body weight, n = 30; rates, succeeding hours; AVP alone, 1.78 +/- 0.22, 0.48 +/- 0.09, 0.16 +/- 0.99 (P < 0.01-0.0005); AVP with amiloride, 1.15 +/- 0.07, 0.93 +/- 0.10, 0.86 +/- 0.08 (no significant fall) ml/kg body weight per h]. Thirty-six preparations treated with arginine vasotocin (AVT, 10-600 microU/ml) showed closely similar responses to those from AVP. These studies extend results to fetal guinea pigs, and show that AVP, at concentrations reported at delivery, can slow lung liquid production or cause reabsorption by a direct action on the lung. The effect increases close to term, and is due to activation of amiloride-sensitive Na+ channels.
    Journal of developmental physiology 05/1993; 19(5):203-12.
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    ABSTRACT: Transferrin receptors (TfR's) on the syncytiotrophoblast mediate transferrin (Tf) dependent Fe uptake and transfer to the fetus. We studied TfR number and density at the microvillous membrane isolated from guinea pig placentas at day 40, 50 and 64 (near term), together with the K(a) values for the main serum isotransferrins being biantennary Tf(slow) and triantennary Tf(fast). The effect of desialylation of either the microvillous membranes or of Tf(slow) and Tf(fast) on the binding characteristics was also studied. The number of TfR's per mg placenta- or membrane protein increased significantly from day 40 to term (P < 0.01 resp. P < 0.025). The K(a) values for Tf(slow) and Tf(fast) did not change during pregnancy. K(a)Tf(slow) = 0.3 nM-1, K(a)Tf(fast) = 0.19 nM-1 (P < 0.01). It is suggested that the increase in F(e) transfer during pregnancy is directly related to number and density of the TfR's at the syncytial border, and that adaptive adjustment of K(a) values does not play a role in the maturation of the transfer process. The pregnancy dependent shift to iso-transferrins with a higher degree of glycosylation offers no explanation for the increase of F(e) transfer during pregnancy. Desialylation of the microvillous membranes did not effect the binding parameters of Tf(slow) and Tf(fast), unless desialylation surpassed the 50% level. Then Ka values decreased and TfR number increased (P < 0.05). Desialylation of Tf(slow) and Tf(fast) had no effect on K(a) nor on the number of TfR. The maternal fetal interface therefore lacks an asialo-glycoprotein receptor.
    Journal of developmental physiology 05/1993; 19(5):221-6.
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    ABSTRACT: Aim of this study was to investigate how gastrointestinal hormones such as exogenous s.c. caerulein (6 micrograms/kg body weight), secretin (100 U/kg body weight), bombesin (20 micrograms/kg body weight, s.c.), CCK-8 (10 micrograms/kg body weight, i.p.), the CCK-A receptor antagonist L 364,718 (100 micrograms/kg body weight, i.p.), camostate (400 mg/kg body weight per os) which releases endogenous CCK and the coadministration of camostate with atropin (250 micrograms/kg body weight, s.c) or L 364,718 (1 mg/kg) influence milk intake from nipples, gastric emptying, and discharge of pancreatic trypsin content in 10-day-old rat pups. Saline-treated pups served as controls. The non-fasting Wistar rat pups of both sexes were used in littermate order. The suckling lasted for 30 and 45 min, respectively. One pup was used only once. After suckling the pups were decapitated, their stomach and pancreas were removed and weighed. The gastric food content was regarded as intake of milk and expressed as difference between the filled minus empty stomach. Pancreatic trypsin and protein content, plasma CCK level were measured. The exogenous agents did not influence gastric content. The investigated peptides decreased, L 364,718, however, increased the pancreatic trypsin/protein ratio. Camostate increased gastric content by 60% and decreased pancreatic trypsin/protein ratio vs saline by 90%. The gastric and pancreatic effects of camostate were not reversed by atropine or L 364,718. Conclusion: Exogenous and endogenous CCK seem not to influence milk intake while decrease pancreatic trypsin/protein ratio. However, endogenous CCK inhibit gastric emptying. The plasma CCK level was elevated due to the applied CCK-8 and camostate during the observed suckling period.
    Journal of developmental physiology 05/1993; 19(4):149-55.
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    ABSTRACT: To test the hypothesis that growth hormone gene messenger RNA abundance in the fetus is subject to the same effects of thyroid hormone previously demonstrated in other situations, we evaluated the effect of thyroidectomy on pituitary GH mRNA content at three gestational ages in the ovine fetus. One of each twin pair of fetal lambs underwent thyroidectomy at 90, 100 or 110 days gestation. Fetal pituitaries were collected 25-30 days later. Plasma GH and IGF-I were measured as well as pituitary GH mRNA content. Serum growth hormone in the thyroidectomy group was less than in the control twins (129.8 vs 187.6 micrograms/l, P = 0.0. GH mRNA was likewise decreased in pituitaries of thyroidectomy fetuses compared to controls (1.01 vs 1.80 units, P = 0.0006). Serum IGF-I and body weight were similar in the thyroidectomy and control twins. We conclude that the ovine fetus in the final trimester of gestation exhibits effects of thyroid hormone on serum GH and mRNA abundance similar to those seen in postnatal animals.
    Journal of developmental physiology 05/1993; 19(4):165-9.
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    ABSTRACT: The present study was undertaken to assess GH secretory profiles in 12 light-breed foals and their dams during forty days after delivery, and the possible influence of GRF and TRH on plasma GH concentrations in these newborn foals. GH secretory pattern was pulsatile in one day- as well as in forty days-old foals. The number of secretory spikes (10 per 24 h) did not vary between days 1 and 40. In the same times, GH secretion did not show any circadian rhythm either in foals or in their dams. Mean daily plasma concentrations (measured through blood samples collected every 20 min for 24 h) were lower in mares (3.4 +/- 0.3 ng/ml) than in their foals (7.4 +/- 0.9 ng/ml; P < 0.05). This difference resulted from both a lower number of GH spikes per 24 h (5 +/- 2 vs 10 +/- 1; P < 0.01) and from a lower pulse amplitude average (8 +/- 5 vs 16 +/- 1; P < 0.05). In three days- and in six days-old foals, synthetic human GRF (0.3 microgram/kg body wt, i.v.) significantly increased plasma GH concentrations. TRH (3 micrograms/kg body wt, i.v.) did not significantly modify plasma GH.
    Journal of developmental physiology 04/1993; 19(4):143-7.
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    ABSTRACT: G-protein content (G(i) alpha, Gs alpha, Gq/11 alpha G(o) alpha and beta subunits) has been measured in membranes prepared from guinea pig uterus at different stages of pregnancy using SDS-PAGE and immunoblotting. Quantification using HRP- or 125I-labelled IgG as second antibody showed a good correlation between added membrane protein and measured G-protein content. Gs alpha appears as two bands of 45 kDa and 52 kDa respectively, the content of both were comparatively high in the non-pregnant uterus and fell about 4-fold close to term (60-67 days). G(i) alpha showed the converse with low level in membranes from the non-pregnant uterus with level approximately 6-fold higher by term. G(o) alpha exhibited changes similar to G(i) alpha. The changes in the content of Gq/11 alpha where biphasic, with comparatively high levels in membranes from the non-pregnant uterus, a sharp fall early in pregnancy followed by a 3-fold rise by near term. The uterine membrane content of the common beta subunit exhibited changes comparable to that of G(i) alpha and G(o) alpha with a 6-fold rise in content between non- and late-pregnant. Measurement of the effect of GTP gamma S action on phosphatidylinositol phospholipase C activity in uterine membranes with exogenous substrate showed pregnancy-dependent effects. In membranes from the non-pregnant uterus 0.1 microM GTP gamma S caused a modest stimulation of activity of 16 +/- 1.9%, whilst at 100 microM it inhibited the enzyme by 25 +/- 6.48%. In membranes from the late-pregnant guinea pig uterus GTP gamma S at both concentrations caused stimulation of enzyme activity.(ABSTRACT TRUNCATED AT 250 WORDS)
    Journal of developmental physiology 04/1993; 19(3):91-7.