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Depletion of pituitary corticotrophin by reserpine and by a nitrogen mustard
Abstract
A single intraperitoneal injection of reserpine (2.5 mg./kg.) into rats produced a fall in the corticotrophin concentration of the pituitary to 30% of the resting value; recovery was not far from complete at 40 hr. A single injection of a nitrogen mustard caused an even greater loss of pituitary corticotrophin; 24 hr. after the injection the concentration was 10% of the resting value. There is no reason to assume that the effect of reserpine is due to an interference with storage of ACTH in the tissue and is not simply due to the fact that the drug acts as a stressing agent. The shape of the curve representing the fall in pituitary ACTH during the early phases of a sudden stress may be very similar to that of the fall in adrenal ascorbic acid produced by the released ACTH. This suggests that, under these circumstances, resynthesis is slow and the diminishing stores of ACTH in the pituitary reflect mainly the release of the hormone.
... The foundations of basic cardiovascular research at MCO were laid by Murray Saffran, Ph.D., a renowned neuroendocrinologist [2][3][4][5][6] who arrived in 1969 and was the founder of the Biochemistry Department. Before arriving at MCO, Saffran worked at McGill University, Montreal, Canada, where he helped uncover the role of cortisol as a regulator of the body's response to stress [2][3][4][5][6]. ...
... The foundations of basic cardiovascular research at MCO were laid by Murray Saffran, Ph.D., a renowned neuroendocrinologist [2][3][4][5][6] who arrived in 1969 and was the founder of the Biochemistry Department. Before arriving at MCO, Saffran worked at McGill University, Montreal, Canada, where he helped uncover the role of cortisol as a regulator of the body's response to stress [2][3][4][5][6]. At MCO, Saffran continued his endocrinology research and explored the role of insulin in the vascular complications of diabetes [7][8][9][10][11]. ...
Purpose of Review
The study aims to capture the history and lineage of hypertension researchers from the University of Toledo in Ohio and showcase their collective scientific contributions dating from their initial discoveries of the physiology of adrenal and renal systems and genetics regulating blood pressure (BP) to its more contemporary contributions including microbiota and metabolomic links to BP regulation.
Recent Findings
The University of Toledo College of Medicine and Life Sciences (UTCOMLS), previously known as the Medical College of Ohio, has contributed significantly to our understanding of the etiology of hypertension. Two of the scientists, Patrick Mulrow and John Rapp from UTCOMLS, have been recognized with the highest honor, the Excellence in Hypertension award from the American Heart Association for their pioneering work on the physiology and genetics of hypertension, respectively. More recently, Bina Joe has continued their legacy in the basic sciences by uncovering previously unknown novel links between microbiota and metabolites to the etiology of hypertension, work that has been recognized by the American Heart Association with multiple awards. On the clinical research front, Christopher Cooper and colleagues lead the CORAL trials and contributed importantly to the investigations on renal artery stenosis treatment paradigms. Hypertension research at this institution has not only provided these pioneering insights, but also grown careers of scientists as leaders in academia as University Presidents and Deans of Medical Schools. Through the last decade, the university has expanded its commitment to Hypertension research as evident through the development of the Center for Hypertension and Precision Medicine led by Bina Joe as its founding Director.
Summary
Hypertension being the top risk factor for cardiovascular diseases, which is the leading cause of human mortality, is an important area of research in multiple international universities. The UTCOMLS is one such university which, for the last 6 decades, has made significant contributions to our current understanding of hypertension. This review is a synthesis of this rich history. Additionally, it also serves as a collection of audio archives by more recent faculty who are also prominent leaders in the field of hypertension research, including John Rapp, Bina Joe, and Christopher Cooper, which are cataloged at Interviews.
... Although release of gastrin may account for the elevation of HFC in the gastric mucosa it cannot be responsible for the reduction of HFC in the lung produced by reserpine since gastrin did not affect the HFC in the lung. The effect produced by reserpine in the lung, which amounted to nearly disappearance of its histidine decarboxylating activity, could on the other hand be explained by an action of corticosteroids, because reserpine releases corticosteroids, as shown in the rat by Saffran & Vogt (1960), and, as mentioned earlier, cortisone lowers the HFC in the lung. Since cortisone increases the HFC in gastric mucosa as well, the HFC elevation produced by reserpine in this tissue could be a combined effect of gastrin and corticosteroids, the reduction of HFC produced in the lung an effect of the corticosteroids alone. ...
. In rats the effect of reserpine, adrenaline and gastrin on the histamine forming capacity (HFC) of gastric mucosa and lung was examined.
. Intraperitoneal reserpine as well as subcutaneous adrenaline produced a great increase in HFC of gastric mucosa but a great decrease in HFC of lung. After reserpine the HFC of lung was almost abolished.
. As the HFC changes produced by reserpine occurred also after demedullation of the suprarenale—the changes in the mucosa were in fact accentuated—release of the medullary hormones by the reserpine does not account for these changes.
. Subcutaneous gastrin caused a great increase in HFC of the gastric mucosa but did not affect the HFC in lung.
. The possible role of release of gastrin and corticosteroids for the reserpine‐induced HFC changes is discussed because it is known that reserpine releases gastrin and corticosteroids and that cortisone produces HFC changes in gastric mucosa and lung.
Reserpine (Fig. 1), an alkaloid derived from the roots of certain species of Rauwolfia, was isolated in 1952, and about 50 Rauwolfia alkaloids are known. Extracts of Rauwolfia, a plant genus belonging to the Apocynaceae family, were used by the Hindus for a variety of diseases including snake bites because of the resemblance of the roots to a snake (Rauwolfia serpentina). It was also used for the treatment of cardiovascular diseases, insomnia, and insanity (Weiner 1985). Reference to the medical use of Rauwolfia alkaloids appeared in the Western literature as early as 1563 (Bein 1956). In 1931 Sen and Bose reported in the Indian Medical Journal that the whole root could be used for the treatment of hypertension and psychosis. Widespread interest in their use for the treatment of hypertension, however, was aroused much later after Vakil (1949) published his findings on the use of Rauwolfia alkaloids in the British Heart Journal. Parental usage became popular for hypertensive emergencies but has a tendency to produce excessive sedation.
It is well known that reserpine causes an increase in pituitary ACTH secretion. A single injection of the drug results in a marked decrease of hypothalamic CRF (corticotrophic releasing factor, Bhattacharya and Marks 1969) and pituitary ACTH content (Kitay et al. 1959, Saffran and Vogt 1960, Maickel et al. 1961, Bhattacharya and Marks 1969) and a simultaneous elevation in plasma corticosterone levels (Maickel et al. 1961, Bhattacharya and Marks 1969). Administration of reserpine for several days leads to adrenal hypertrophy (Gaunt et al. 1954, Hertting and Hornykiewicz 1957, Montanari and Stockham 1962).
It is now forty years since Smith (1927) showed that removal of the pituitary gland from various animal species results in atrophy of their adrenal cortices which can be prevented by the daily injection of anterior pituitary extracts or by transplants of adenohypophysial tissue. Thus, the existence of a trophic hormone responsible for the maintenance of the adrenal cortices was clearly shown. This hormone is called adrenocorticotrophic hormone, corticotrophin or ACTH. It is a comparatively simple polypeptide which varies slightly according to the species from which it is obtained. The chemical structures are known and some have been synthesised.
Preparations derived from species of Rauwolfia, a plant genus belonging to the Apocynaceae family, have been used for the treatment of a great variety of diseases in the folk medicine of the regions in which they are found. The species R. serpentina is a climbing or twining shrub occurring in the Indian sub-continent and S.E. Asia. The root of this plant has been used since ancient times in both India and the Malay peninsula as an antidote to the stings and bites of insects and poisonous reptiles. It has also been used to reduce fever, as a stimulant to uterine contractions, for insomnia, and particularly for the treatment of insanity.
In 1955 Shore, Brodie and coworkers (Shore, Silver and Brodie 1955, Pletscher, Shore and Brodie 1955) discovered that reserpine caused a marked decrease in the concentration of 5-hydroxytryptamine (5-HT) in tissues and a concomitant rise in the urinary excretion of the 5-HT metabolite 5-hydroxyindoleacetic acid. The deep physiological significance of this discovery became even more evident when reserpine soon afterwards was found to affect tissue catecholamines in a similar manner, an effect leading to block of adrenergic transmission mechanisms (Carlsson and Hillarp 1956a, Bertler, Carlsson and Rosengren 1956). Since then numerous papers have appeared, in which the effects of Rauwolfia alkaloids and a group of similarly acting benzoquinolizines (Pletscher, Besendorf and Bächtold 1958) have been further analyzed. Particular interest has been focussed on the mechanism of action on the abovementioned amines and on the relationship between this action and the various pharmacological effects of Rauwolfia alkaloids and benzoquinolizines. It is the aim of the present Chapter to review and discuss the pertinent literature dealing with these fundamental problems rather than to review in detail the enormous literature on the pharmacology of these agents.
According to reports in the literature [1,4-10,18, 19], monoamines of the central nervous system (especially of the hypothalamus) possibly play a role in regulating the adrenocorticotro pic (ACT) function of the pituitary. Conclusions that catecholamines (CA) of the hypothalamus participate in regulation of pituitary ACT function were based on experiments with reserpine, a substance exhausting monoamine reserves in the tissues, and are highly contradictory [2, 9-12, 14, 17]. The reason for this is that the compound was given by different methods and ia different doses, and different tests were used to assess the results at different times. In this investigation the CA level in the hypothalamus and the ACT function of the pituitary was found to be mutually dependent. EXPERIMENTAL METHOD Noninbred male rats weighing 160-200 g were used. The animals of 4 experimental groups received 0.2 and 2 mg/kg reserpine (Rausidil, Gedeon Richter, Hungary) by intramuscular injection, while the animals of 4 control groups received physiological saline in the same volume. The animals were sacrificed 3 and 24 h after injection of the preparations. Plasma and pituitary ACT activity was determined by the biological method of Vernikos and Danellis in V. M. Rozental's modification, and the adrenalin (A) and noradrenalin (NA) concentrations in the plasma, adrenals, and hypothalamus were determined by the fluorimetric method of Euler and Lishaiko as modified
1.1. Experiments with reserpine on Xenopus of different background histories suggest that long-term exposure to a white background leads to a depletion of MSH in the pars intermedia.2.2. A model involving the brain monoamines (serotonin and catecholamines) for the control of the pars intermedia is proposed.3.3. This follows an explanation for the MSH-releasing effect of reserpine observed by various authors.4.4. A possible ACTH-releasing effect of reserpine in Xenopus is also considered.
Reserpine treatment has been shown to cause a long-lasting decrease in phenylethanolamine N-methyltransferase mRNA levels and a simultaneous increase in tyrosine hydroxylase and neuropeptide tyrosine mRNA levels in chromaffin cells of rat adrenal medulla. In this study, in situ hybridization histochemistry was used to further investigate factors involved in the differential regulation of the catecholamine synthesizing enzymes and the coexisting peptide neuropeptide tyrosine. Pretreatment with the synthetic glucocorticoid analogue dexamethasone followed by the administration of a single dose of reserpine completely reversed the decrease in phenylethanolamine N-methyltransferase mRNA seen after reserpine treatment alone, but had no effect on the reserpine-induced increase in tyrosine hydroxylase mRNA. Dexamethasone alone did not change phenylethanolamine N-methyltransferase or tyrosine hydroxylase mRNA levels in the adrenal medulla. When reserpine-treated rats were given adrenocorticotropic hormone a partial reversal of the decrease in phenylethanolamine N-methyltransferase mRNA was seen. Furthermore, the reserpine-induced increase in neuropeptide tyrosine mRNA levels was markedly reduced when animals were pretreated with dexamethasone, whereas dexamethasone alone had no effect on neuropeptide tyrosine mRNA levels. The drop in phenylethanolamine N-methyltransferase mRNA levels after reserpine treatment was not due to a depression of the pituitary adrenal axis, since proopiomelanocortin mRNA levels in the anterior pituitary increased and plasma corticosterone levels were stable following reserpine treatment. A possible local regulation within the adrenal gland that may involve the glucocorticoid receptor and/or other factors is discussed.
The effect of reserpine on hypothalamo‐pituitary‐adrenocortical (HPA) function in the rat was investigated by the use of direct and indirect indices of pituitary adrenocorticotrophic activity.
Administration of a single dose of the drug induced prolonged hypersecretion of corticotrophin (ACTH).
Corticotrophin release in response to the drug no longer occurred after repeated daily injections, indicating that some form of ‘adaptation’ occurred.
The increase in HPA activity normally caused by exposure to cold was prevented by reserpine once ‘adaptation’ to the drug had been produced.
Inhibition of stress‐induced ACTH release was due neither to depletion of pituitary stores of the hormone, nor to a corticosteroid feedback effect.
Using in situ hybridization and immunohistochemistry, we have studied mRNA and peptide levels in the hypothalamic paraventricular nucleus (PVN) 24 h after a single large dose of reserpine (10 mg/kg, i.p.) and 24 h after an intraventricular (i.c.v.) injection of colchicine (120 microliters/20 microliters saline). Sections of the PVN were hybridized using synthetic oligonucleotide probes complementary to mRNA for corticotropin-releasing hormone (CRH), neurotensin (NT), enkephalin (ENK), vasoactive intestinal polypeptide (VIP) and thyrotropin-releasing hormone (TRH). For immunohistochemistry rabbit antisera to CRH, NT, ENK, VIP and TRH were used. In situ hybridization showed a clear increase in CRH mRNA as compared to control rats after both treatments. Also NT and VIP mRNA could be seen in parvocellular neurons in reserpine and in colchicine-treated rats, whereas we so far have not been able to demonstrate these mRNAs in untreated rats. No changes in TRH mRNA could be detected after reserpine of colchicine. These results provide final evidence that subpopulations of parvocellular PVN neurons can synthesize not only CRH and ENK, but also NT and VIP, in agreement with earlier immunohistochemical results. With immunochemistry, after reserpine, many CRH-, but no NT- or VIP- positive neurons could be observed in the parvoecellular part of the PVN. The present results demonstrate that treatment with two drugs, the monoamine depleting drug reserpine and the mitosis inhibitor colchicine, causes increased levels of mRNA for several peptides in neurons of the PVN, located almost exclusively in its parvocellular part and being part of the hypothalamo-pituitary adrenal axis.
This autobiography traces the effects of "marriages" of different fields on the development of new directions of research. Such events occurred several times in my career and generated much of my research.
Expression and regulation of the catecholamine-synthesizing enzymes phenylethanolamine N-methyltransferase (PNMTase; S-adenosyl-L-methionine:phenylethanolamine N-methyltransferase, EC 2.1.1.28) and tyrosine hydroxylase [TyrOHase; tyrosine 3-monooxygenase, L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2] and the coexisting neuropeptide tyrosine (NPY) were studied in rat and bovine adrenal medulla. By using both immunohistochemistry and in situ hybridization, PNMTase- and NPY-positive cells exhibited a close overlap in bovine medulla and were preferentially localized in the outer two-thirds of the medulla. Although TyrOHase and its mRNA were observed in virtually all medullary gland cells, TyrOHase mRNA levels were much higher in the PNMTase- and NPY-positive cells. After administration of the catecholamine-depleting drug reserpine to rats, a brief increase, followed by a dramatic decrease, in the level of PNMTase mRNA was observed in the adrenal medulla. In contrast, mRNA for both TyrOHase and NPY only exhibited an increase, whereby the TyrOHase mRNA peak preceded that of NPY mRNA. Different regulatory mechanisms may thus operate for these three compounds coexisting in the adrenal medulla.
Summary The studies were concerned with the site in the CNS of the action of reserpine on pituitary ACTH secretion. The medial basal hypothalamus (MBH) was totally or partially deafferented (interrupting the anterior, the posterior and superior or the posterior connections of the region and leaving intact all the other pathways), the fornix was transected or a lesion was placed in the medial ventral tegmentum of the mesencephalon, and following all these interventions plasma corticosterone levels were determined before reserpine treatment and four hours after drug administration (giving 3.0–3.5 mg/kg b.w. i.p.). In the intact rats reserpine caused a 3–5 fold increase in plasma corticosterone concentration. No elevation in blood corticoid levels occurred if the drug was administered to rats in which the MBH was completely deafferented. Similar results were obtained when only the anterior connections of the MBH were interrupted. In contrast, severance of the afferents coming to the MBH from both sides and from above, or from posterior, transection of the fornix, or a lesion in the medial ventral tegmentum of the mesencephalon did not block the mentioned effect of reserpine. The drug given to intact rats for nine days (0.7 mg/kg b.w. daily i.p.) induced a well-known marked increase in adrenal weight. Complete deafferentation of the MBH also interfered with this effect. — The data suggest that (1) the reserpine-induced CRF release is not directly exerted on the MBH; (2) the critical afferents essential for the pituitary ACTH response to reserpine reach the MBH from an anterior direction; (3) hippocampal and mesencephalic structures having direct contact with the MBH are not primarily responsible for the reserpine effect on ACTH.
The effects of reserpine and chlorpromazine on cold stress-induced changes in adrenal ascorbic acid of rats and blood glucose, serum cholesterol, and serum sodium levels of rabbits were studied. While pretreatment with chlorpromazine minimized many of these stress-induced alterations, reserpine pretreatment aggravated them. Reserpine was found to be effective in preventing the stress-induced reduction of serum cholesterol level. Pretreatment with chlorpromazine minimized the adrenal ascorbic acid depletion due to cold stress. It also significantly prevented rise in blood sugar and fall in serum sodium produced by cold stress.
A single injection into the rat of chlorpromazine, reserpine, benactyzine or phenobarbitone stimulates the release of corticotrophin. This effect is not seen after the drugs have been injected daily for 5 days, nor when the rats are hypophysectomized or pretreated with hydrocortisone. The stimulant effect of ether on corticotrophin release is not modified by pretreatment with a single injection, nor to any great extent after 5 daily injections of these drugs.
The effects of single and repeated doses of reserpine on the secretion of adrenocorticotrophic hormone (ACTH) were studied in rats by determining changes in the adrenal and plasma concentrations of corticosterone, in the adrenal ascorbic acid levels, and in the adrenal gland weights. Treatment with doses of reserpine which induced sedation caused prolonged hypersecretion of ACTH. Such treatment did not impair the release of ACTH in response to a stressful stimulus as recorded by an increase in the plasma corticosterone even when there was no concomitant depletion in the adrenal ascorbic acid. This finding casts doubt on the value of the adrenal ascorbic acid determination as an index of ACTH secretion.
The highly vascular, anteromedial zone of hog and beef pituitary glands, which is rich in basophilic cells, contains a concentration of ACTH from 4 to 13 times that found in the rest of the adenohypophysis. The concentration of ACTH can be correlated (r = 0.96) with the relative proportion of basophilic cells, supporting the view that the pituitary basophiles are the source of ACTH. The distribution of both basophiles and ACTH in the rat adenohypophysis is more uniform than in hog or beef glands. The posterior lobe of all species examined (rat, hog, beef, and man) contains small, but significant, amounts of ACTH.
From planimetric measurements of the total gland and its components, at progressively later intervals following unilateral adrenalectomy and contralateral enucleation in the rat, full regeneration of the cortex was observed to occur within 6–8 weeks. Free corticosteroids disappeared from the plasma within 6–8 hours of the enucleation procedure. Their subsequent rise, already detectable on the 4th day, culminated in a transient and slightly supernormal peak on the 16th day. From a correlation of the plasma free corticosteroid levels to the corresponding amounts of cortex, the secretory activity of the regenerating gland per unit of cortical tissue was estimated at 570% of the paired-weight control base line after 16 days, and at slightly above 200% after 7 weeks, when it leveled off. The pituitary ACTH response to the procedure was characterized by a transient rise within the first 15 minutes, followed by a fall to 35% of the control level after 4 hours, and to 22% after 12, subsequent rise to a crest of 330% on the 16th day, and regression thereafter to near-normal values, recorded on the 184th day. The concomitant rises and falls of pituitary ACTH, cortical secretory index and plasma free corticosteroids, observed in association with cortical deficiency and regeneration, reinforce the conclusion, reached from previous studies, that both release and synthesis of ACTH are accelerated by hypo- and depressed by hypercorticoidism, and that, furthermore, the regulatory effect of steroids is predominantly exerted on synthesis.
Pituitary ACTH and plasma free corticosteroids were concurrently determined following bilateral adrenalectomy in the rat. Free corticosteroids disappeared from the plasma within 4 hours. Pituitary ACTH rose to 150% of the control level within the first 30 minutes, fell to 40% after 4 hours, to 30% after 12, stabilized at this level for the next 12 hours, rose from then on to supernormal levels, up to a crest of 575% on the 32nd day, and regressed, thereafter, to lower, though still markedly elevated, values. From a correlation of these findings with available data on blood ACTH levels under comparable conditions, it is inferred that, following a transient burst of synthesis reflected by the initial peak, a predominant, though gradually receding, acceleration of the rate of release accounts for the pituitary ACTH depletion, a greater and sustained acceleration of synthesis, for its subsequent rise. It is further suggested that the ACTH-releasing effect of stress is markedly influenced by the level of circulating adrenal cortical hormones, and that withdrawal of these hormones enhances both release and synthesis of ACTH, but has a predominant effect on the latter.
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