Article

Pituitary and gonadal response to exogenous LH-releasing hormone in the male domestic cat

Department of Obstetrics/Gynecology , Uniformed Services University of the Health Sciences, 베서스다, Maryland, United States
Journal of Endocrinology (Impact Factor: 3.72). 06/1985; 105(2):175-81. DOI: 10.1677/joe.0.1050175
Source: PubMed

ABSTRACT

To determine the influence of exogenous LH-releasing hormone (LHRH) on serum LH and testosterone, ten adult male domestic cats received three treatments on a rotating schedule at 10-day intervals as follows: (I) 0.1 ml saline i.m. (control); (II) 10 micrograms LHRH i.m., single injection; (III) 10 micrograms LHRH i.m., two injections given at a 2-h interval. Serial blood samples collected over a 360-min interval were analysed by radio-immunoassay for LH and testosterone. Although baseline serum LH values in saline-treated animals (treatment I) varied markedly among individual cats (2.2-29.2 micrograms/l), there was no evidence of pulsatile LH release or alterations in testosterone over time within individual males. In treatment II, the single injection of LHRH induced a rapid rise in mean serum LH within 30 min in all cats (mean peak, 88.2 +/- 9.8 micrograms/l), which returned to baseline by 120 min after LHRH. Mean testosterone increased within 30 min in this group (from 6.03 +/- 2.18 to 18.55 +/- 3.36 nmol/l), peaked at the 60-min collection (19.76 +/- 2.77 nmol/l) and returned to baseline by the 150-min sample. After treatment III, serum LH peaked at 131.6 +/- 13.6 micrograms/l within 30 min of the initial LHRH injection. A second injection of LHRH produced another LH surge within 30 min, but in all cats this second response was of a lower magnitude (mean peak, 69.0 +/- 14.5 micrograms/l) and shorter duration (P less than 0.05). The second LHRH injection sustained peripheral testosterone levels for approximately 1 additional h.(ABSTRACT TRUNCATED AT 250 WORDS)

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    • "Androgens are essential for most stages of spermatogenesis (Mann & Lutwak-Mann, 1981); however, it is not known whether circulating testosterone concentrations in some felid species with compromised sperm morphology are suboptimal for sustaining normal spermatogenic function. The observation of depressed testosterone values in some species or populations, despite similar immunoreactive concentrations of the con¬ trolling hormone LH (Goodrowe et ai, 1985; Wildt et ai, 1986a, 1987, 1988; Brown et ai, 1988), suggests that compromised genotype probably affects the gonad and not the pituitary. However, alterations in bioactivity ofthe secreted gonadotrophins may also be involved. "
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    ABSTRACT: In Study 1, semen was collected using a standardized electroejaculation procedure. Males (N = 8) produced ejaculates with a high incidence of sperm abnormalities (77 +/- 3.3%). After electroejaculation under anaesthesia, serum cortisol concentrations increased (P less than 0.05), while testosterone concentrations decreased (P less than 0.05) and LH and FSH concentrations were unchanged (P less than 0.05) over a 2-h bleeding period. In Study 2, male and female leopards were bled at 5-min intervals for 3 h and given (i.v.): (1) saline (N = 2/sex); (2) GnRH (1 microgram/kg body weight) 30 min after the onset of sampling (N = 5/sex); or (3) ACTH (250 micrograms) at 30 min followed by GnRH 1 h later (N = 5/sex). Basal concentrations of serum LH, FSH and cortisol were comparable (P greater than 0.05) between male and female leopards. After GnRH, peak LH concentrations were 2-fold greater (P less than 0.05) in males than females while FSH responses were similar. In males, testosterone concentrations increased 2-3-fold following GnRH. After ACTH, serum cortisol concentrations doubled within 15 min in both sexes. Administration of ACTH 1 h before GnRH did not affect GnRH-induced LH or FSH release (P greater than 0.05); however, testosterone secretion was only 30% of that observed after GnRH alone (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
    Full-text · Article · Apr 1989 · J Reprod Fertil
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    • "Basal testosterone concentrations in leopards were about 30% those in tigers, and these concentrations, in turn, were much lower than values previously reported for the domestic cat, clouded leopard and puma (Goodrowe et al, 1985; Wildt et al, 1986a, 1987a). The lower basal testosterone concentrations of North Chinese leopards cannot be explained by inadequate gonado¬ trophin stimulation since LH concentrations were similar to those observed in the tiger, as well as values previously reported for other felids (Wildt et al, 1984a, b, 1987a; Goodrowe et al, 1985). Taken together, these data serve to identify marked functional differences in the hypothalamopituitary-gonadal axis of the North Chinese leopard and tiger. "
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    ABSTRACT: Frequent blood samples were collected to study hormonal responses to GnRH in male and female leopards and tigers. Animals were anaesthetized with ketamine-HCl and blood samples were collected every 5 min for 15 min before and 160 min after i.v. administration of GnRH (1 micrograms/kg body weight) or saline. No differences in serum cortisol concentrations were observed between sexes within species, but mean cortisol was 2-fold greater in leopards than tigers. GnRH induced a rapid rise in LH in all animals (18.3 +/- 0.9 min to peak). Net LH peak height above pretreatment levels was 3-fold greater in males than conspecific females and was also greater in tigers than leopards. Serum FSH increased after GnRH, although the magnitude of response was less than that observed for LH. Basal LH and FSH and GnRH-stimulated FSH concentrations were not influenced by sex or species. Serum testosterone increased within 30-40 min after GnRH in 3/3 leopard and 1/3 tiger males. Basal testosterone was 3-fold greater in tiger than leopard males. LH pulses (1-2 pulses/3 h) were detected in 60% of saline-treated animals, suggesting pulsatile gonadotrophin secretion; however, in males concomitant testosterone pulses were not observed. These results indicate that there are marked sex and species differences in basal and GnRH-stimulated hormonal responses between felids of the genus Panthera which may be related to differences in adrenal activity.
    Full-text · Article · Feb 1988 · J Reprod Fertil
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    • "Androgens are essential for most stages of spermatogenesis (Mann & Lutwak-Mann, 1981); however, it is not known whether circulating testosterone concentrations in some felid species with compromised sperm morphology are suboptimal for sustaining normal spermatogenic function. The observation of depressed testosterone values in some species or populations, despite similar immunoreactive concentrations of the con¬ trolling hormone LH (Goodrowe et ai, 1985; Wildt et ai, 1986a, 1987, 1988; Brown et ai, 1988), suggests that compromised genotype probably affects the gonad and not the pituitary. However, alterations in bioactivity ofthe secreted gonadotrophins may also be involved. "
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    ABSTRACT: of sperm abnormalities in the leopards of Sri Lanka may be related to parallel findings of genetic homozygosity; and (2) decreases in basal and GnRH-stimulated testosterone secretion were related to increases in serum cortisol after electroejaculation or ACTH and were not associated with changes in pituitary gonadotrophin secretion.
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