Hypothalamic release of atrial natriuretic factor and β-endorphin into rat hypophysial portal plasma: relationship to oestrous cycle and effects of hypophysectomy

1991 ◽  
Vol 131 (1) ◽  
pp. 113-125 ◽  
Author(s):  
W. J. Sheward ◽  
A. Lim ◽  
B. Alder ◽  
D. Copolov ◽  
R. C. Dow ◽  
...  
Keyword(s):  
Plasma Concentrations ◽  
Portal Blood ◽  
Female Rats ◽  
Male Rats ◽  
Blood Collection ◽  
Peripheral Plasma ◽  
Portal Plasma ◽  
Hypophysectomized Rats ◽  
Hypophysial Portal

ABSTRACT The release of β-endorphin and atrial natriuretic factor (ANF) into hypophysial portal plasma was investigated in male and female Wistar rats. The principal aim of the study was to investigate the possible role of β-endorphin and ANF in the hypothalamic control of LH and prolactin secretion. In male rats, anaesthetized with urethane, the concentrations of β-endorphin in portal blood collected immediately after hypophysectomy were within the same range as those in peripheral plasma. Furthermore, electrical stimulation of the median eminence did not increase the portal plasma concentrations of β-endorphin. In female rats, anaesthetized with alphaxalone, the portal plasma concentrations in long-term (6–8 weeks) or acutely hypophysectomized rats were significantly greater than those in peripheral plasma. In acutely hypophysectomized female rats the concentrations and contents of β-endorphin in portal plasma collected at 10.00–11.30 h of pro-oestrus were significantly (approximately sixfold) greater than at dioestrus or at 20.00–21.00 h of pro-oestrus, but these changes were not consistently seen in all experiments. In female rats in which the pituitary gland was not removed for portal blood collection, portal plasma contents of ANF remained unchanged throughout the day of pro-oestrus, suggesting that it is unlikely that ANF is involved in the spontaneous LH or prolactin surge. The effects of ovarian steroids on the secretion of hypothalamic ANF and β-endorphin were determined by measuring the portal plasma concentration of ANF and β-endorphin on the morning of presumptive pro-oestrus in rats ovariectomized 24 h previously and injected with either oil or oestradial benzoate (OB). Portal plasma contents of ANF were significantly lower in OB- compared with oil-treated rats, suggesting that oestradiol inhibits ANF release into rat hypophysial portal plasma. In contrast, there were no significant between-group differences in the content or concentration of β-endorphin in portal plasma. Thus, the increased β-endorphin in the portal plasma of some of the intact animals during the morning of pro-oestrus is not due to the preovulatory surge of oestradiol-17β. The output of β-endorphin into portal blood in long-term hypophysectomized rats was lower than in dioestrous or pro-oestrous rats in which the pituitary gland was removed immediately before portal blood collection. Taken together, these results suggest that β-endorphin release into portal plasma may depend upon normal physiological levels of pituitary and pituitary-dependent hormones in the circulation, and that β-endorphin release into portal blood is not controlled by short- or long-loop negative feedback. In sum, these data confirm that in adult female rats, ANF and β-endorphin are released into hypophysial portal plasma and show (i) that the secretion of ANF, but not of β-endorphin, can be affected by oestradiol, (ii) that the concentrations of ANF in portal plasma are sufficient to affect the release of pituitary hormones but are not related to plasma concentrations of LH and prolactin during the afternoon of pro-oestrus, (iii) that whilst there is no simple inverse relationship between βendorphin overflow into portal plasma and LHRH secretion, the increased release of β-endorphin during the morning of pro-oestrus may be consistent with a role for this peptide in triggering the pro-oestrous surge of pro-lactin, and (iv) that a sex difference in β-endorphin release into portal plasma is suggested by the absence of β-endorphin in the portal plasma of male rats. Journal of Endocrinology (1991) 131, 113–125

Concentrations of dopamine and noradrenaline in hypophysial portal blood in the sheep and the rat

1989 ◽  
Vol 121 (1) ◽  
pp. 141-147 ◽  
Author(s):  
G. B. Thomas ◽  
J. T. Cummins ◽  
G. A. Smythe ◽  
R. M. Gleeson ◽  
R. C. Dow ◽  
...  
Keyword(s):  
Plasma Concentrations ◽  
Portal Blood ◽  
Female Rats ◽  
Male Rats ◽  
Gas Chromatography Mass Spectrometry ◽  
Intact Male ◽  
Peripheral Plasma ◽  
Portal Plasma ◽  
Urethane Anaesthesia ◽  
Hypophysial Portal

ABSTRACT The concentrations of dopamine, noradrenaline and their respective primary neuronal metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and 3,4-dihydroxyphenylethyleneglycol (DHPG) were measured in the hypophysial portal and peripheral plasma of sheep and rats by combined gas chromatography–mass spectrometry. Hypophysial portal and jugular blood samples were taken at 5- to 10-min intervals for 3–7 h from six conscious ovariectomized ewes. Blood was also collected for 30 min under urethane anaesthesia from the cut pituitary stalk from 16 pro-oestrous female and five intact male rats. In ovariectomized ewes, noradrenaline concentrations were higher in hypophysial portal plasma than in peripheral plasma (6·6 ± 0·8 vs 2·2 ± 0·4 nmol/l). In contrast, dopamine was undetectable (<1 nmol/l) in the portal and peripheral plasma of all ewes. Plasma levels of DOPAC and DHPG in portal and jugular samples were similar. In all pro-oestrous female rats, plasma concentrations of dopamine were higher in portal blood than in jugular blood (8·0±1·4 vs 4·8± 0·6 nmol/l). Detectable concentrations of dopamine were measured in the portal plasma of two out of five male rats. Noradrenaline concentrations were higher in portal plasma than in peripheral plasma of both female (8·3 ± 1·7 vs 3·7 ± 0·6 nmol/l) and male (14·8± 2·7 vs 6·1± 1·2 nmol/l) rats. These data show that noradrenaline, but not dopamine, is secreted into the long portal vessels in sheep. The results suggest that there are species differences in the secretion of hypothalamic dopamine into hypophysial portal blood. Journal of Endocrinology (1989) 121, 141–147

Effects of corticosterone on the secretion of corticotrophin-releasing factor, arginine vasopressin and oxytocin into hypophysial portal blood in long-term hypophysectomized rats

1991 ◽  
Vol 129 (1) ◽  
pp. 91-98 ◽  
Author(s):  
W. J. Sheward ◽  
G. Fink
Keyword(s):  
Arginine Vasopressin ◽  
Portal Blood ◽  
Blood Collection ◽  
Continuous Administration ◽  
Feedback Effects ◽  
Corticotrophin Releasing Factor ◽  
Hypophysectomized Rats ◽  
Hypophysial Portal ◽  
Intact Rats

ABSTRACT To investigate the feedback effects of corticosterone on the secretion of corticotrophin-releasing factor-41 (CRF-41), oxytocin and arginine vasopressin (AVP), hypophysial portal vessel blood was collected from control (intact) and long-term (6–8 weeks) hypophysectomized rats. In preliminary experiments in rats anaesthetized with urethane, long-term hypophysectomy resulted in a significant increase in the secretion of oxytocin and AVP; the hypothalamic contents of oxytocin and AVP were also increased in comparison with pituitary-intact rats. In long-term hypophysectomized rats anaesthetized with sodium pentobarbitone, but not with urethane, the output of CRF-41 into portal blood was increased twofold in comparison with that in control rats. In long-term hypophysectomized rats anaesthetized with pentobarbitone, the i.v. infusion of corticosterone (7·2 nmol/min) for a 2 h period of portal blood collection did not alter the secretion of CRF-41, oxytocin or AVP into portal blood; however, the secretion of CRF-41 and, to a lesser extent, AVP was significantly reduced in hypophysectomized rats by continuous corticosterone replacement, by a pellet of corticosterone implanted s.c. for 5 days before portal blood collection. These results confirm that the secretion of CRF-41 is differently affected by the anaesthetics urethane and pentobarbitone, and in long-term hypophysectomized rats show (i) that there were no apparent feedback effects of corticosterone infusion over a 2 h period on the secretion of any of the peptides studied, (ii) that late delayed feedback effects of continuous administration of corticosterone are mediated by a reduction in CRF-41 and AVP output, and (iii) that corticosterone has no effects on oxytocin secretion into portal blood. Journal of Endocrinology (1991) 129, 91–98

Radioimmunoassay of inhibin in various mammals

1989 ◽  
Vol 122 (3) ◽  
pp. 697-704 ◽  
Author(s):  
T. Hamada ◽  
G. Watanabe ◽  
T. Kokuho ◽  
K. Taya ◽  
S. Sasamoto ◽  
...  
Keyword(s):  
Adult Male ◽  
Follicular Fluid ◽  
Plasma Concentrations ◽  
High Titre ◽  
Female Rats ◽  
Male Rats ◽  
Pituitary Cells ◽  
Peripheral Plasma ◽  
Male And Female Rats ◽  
Tissue Homogenates

ABSTRACT A sensitive radioimmunoassay (RIA) for the determination of inhibin in peripheral plasma and tissue homogenates of different species has been developed using antisera to partially purified bovine follicular fluid (bFF) inhibin and 125I-labelled bFF 32 kDa inhibin. Antisera were produced by immunization of rabbits with partially purified bFF inhibin prepared by immunoaffinity chromatography. Increasing doses of a high titre antiserum could neutralize the suppressing effect of bFF, porcine follicular fluid and rat ovarian homogenate on FSH secretion from rat anterior pituitary cells in culture. Sensitivity of the assay was 3·1 ng International Research Standard of porcine inhibin per tube. Parallel inhibition curves were obtained for inhibin preparations from female and male animals of ten species, i.e. cattle, goats, sheep, cats, dogs, monkeys, pigs, horses, rats and man. Inhibin subunits and related proteins cross-reacted minimally with the antiserum used in the study. Plasma concentrations of inhibin in adult male and female rats were measured by the RIA before and at various times after gonadectomy. Inhibin levels in peripheral plasma before gonadectomy were significantly higher in adult female than in adult male rats. Inhibin levels decreased abruptly after gonadectomy in both sexes and they correlated negatively with plasma concentrations of FSH. This inhibin RIA will facilitate studies of the physiology of inhibin in various species of animals. Journal of Endocrinology (1989) 122, 697–704

Release of oxytocin but not corticotrophin-releasing factor-41 into rat hypophysial portal vessel blood can be made opiate dependent

1990 ◽  
Vol 124 (1) ◽  
pp. 141-150 ◽  
Author(s):  
W. J. Sheward ◽  
J. E. Coombes ◽  
R. J. Bicknell ◽  
G. Fink ◽  
J. A. Russell
Keyword(s):  
Portal Blood ◽  
Morphine Dependence ◽  
Opiate Withdrawal ◽  
Portal Vessel ◽  
Peripheral Plasma ◽  
Corticotrophin Releasing Factor ◽  
Intracerebroventricular Infusion ◽  
Oxytocin Release ◽  
Hypophysectomized Rats ◽  
Hypophysial Portal

ABSTRACT The effects of morphine dependence and abrupt opiate withdrawal on the release of oxytocin and corticotrophin-releasing factor-41 (CRF-41) into hypophysial portal vessel blood in rats anaesthetized with urethane were investigated. Adult female Sprague–Dawley rats were made dependent upon morphine by intracerebroventricular infusion of morphine for 5 days; abrupt opiate withdrawal was induced by injection of the opiate antagonist naloxone. The basal concentrations of oxytocin in portal or peripheral plasma from morphine-dependent rats did not differ significantly from those in control, vehicle-infused rats. In rats in which the pituitary gland was not removed after stalk section, the i.v. injection of naloxone hydrochloride (5 mg/kg) resulted in a large and sustained increase in the concentration of oxytocin in both portal and peripheral plasma in control and morphine-dependent rats. The i.v. injection of naloxone resulted in a threefold increase in the secretion of oxytocin into portal blood in acutely hypophysectomized rats infused with morphine, but did not alter oxytocin secretion in vehicle-infused hypophysectomized rats. The concentration of oxytocin in peripheral plasma in both vehicle- and morphine-infused hypophysectomized rats was at the limit of detection of the assay and was unchanged by the administration of naloxone. There were no significant differences in the secretion of CRF-41 into portal blood in vehicle- or morphine-infused hypophysectomized rats either before or after the administration of naloxone. These data show that, as for oxytocin release from the neurohypophysis into the systemic circulation, the mechanisms which regulate oxytocin release into the portal vessel blood can also be made morphine dependent. The lack of effect of morphine or naloxone on the release of CRF-41 or other stress neurohormones suggests that the effect of opiate dependence and withdrawal is selective for oxytocin and is not simply a non-specific response to 'stress'. Journal of Endocrinology (1990) 124, 141–150

Oxytocin and vasopressin in rat hypophysial portal blood: experimental studies in normal and Brattleboro rats

1985 ◽  
Vol 104 (2) ◽  
pp. 211-NP ◽  
Author(s):  
A. M. Horn ◽  
I. C. A. F. Robinson ◽  
G. Fink
Keyword(s):  
Electrical Stimulation ◽  
Peripheral Blood ◽  
Wistar Rats ◽  
Plasma Concentrations ◽  
Portal Blood ◽  
Brattleboro Rats ◽  
External Layer ◽  
Portal Plasma ◽  
Hypophysial Portal ◽  
Uptake Blockers

ABSTRACT Oxytocin (OT) and vasopressin (VP) were measured by radioimmunoassay in hypophysial portal and peripheral blood from male Wistar rats and heterozygous and homozygous Brattleboro rats anaesthetized with urethane. In Wistar rats the concentrations of OT and VP were about 50 times greater than the concentrations in peripheral blood, whether or not the pituitary gland was left in situ during collection, and also considerably greater than the reported concentrations of the peptides in the cerebrospinal fluid. The release of both peptides was increased significantly by a lesion of the supraoptico-hypophysial tract that led to diabetes insipidus, but which left intact the external layer of the median eminence (ME). Concentrations of VP were undetectable in plasma from homozygous Brattleboro rats, but the portal plasma concentrations of VP in heterozygous Brattleboro rats were not significantly lower than in Wistar rats. The concentrations of OT in portal plasma from both types of Brattleboro rat were significantly higher than in Wistar rats. The output of VP and OT into hypophysial portal blood of Wistar rats was not significantly affected by electrical stimulation of the suprachiasmatic, supraoptic or paraventricular nuclei or the ME using two types of stimuli, one of which produced an increase in peripheral plasma concentrations of VP and OT in intact rats and a significant increase in the release of LH-releasing hormone into hypophysial portal blood. The output of VP and OT into portal blood was also not significantly affected by either adrenalectomy with or without injection of dexamethasone or the injection of either the 5-hydroxytryptamine (5-HT) synthesis blocker, parachlorophenylalanine, or the 5-HT uptake blockers, alaproclate or zimelidine. These results show that large amounts of OT as well as VP are released into hypophysial portal blood from fibres of the hypothalamo-neurohypophysial system that terminate in the external layer of the ME. Although distinct from the fibres that terminate in the pars nervosa (PN), the findings in Brattleboro rats show that the VP fibres of the ME system originate in neurones with a genomic mechanism for VP synthesis similar to that of the VP neurones that project to the PN. The lack of effect of adrenalectomy and the administration of 5-HT synthesis and uptake blockers must be interpreted with caution since the results obtained with electrical stimulation suggest that when the pituitary stalk is cut the release of OT and VP into portal blood approaches a maximum and may therefore be difficult to alter by experimental manipulation. The concentrations of OT and VP in portal blood are sufficiently high for these peptides to play a significant role in neural control of the anterior pituitary gland. J. Endocr. (1985) 104, 211–224

Corticotrophin-releasing factor-41, vasopressin and oxytocin release into hypophysial portal blood in the rat: effects of electrical stimulation of the hypothalamus, amygdala and hippocampus

1991 ◽  
Vol 129 (1) ◽  
pp. 99-107 ◽  
Author(s):  
L. A. Tannahill ◽  
W. J. Sheward ◽  
I. C. A. F. Robinson ◽  
G. Fink
Keyword(s):  
Electrical Stimulation ◽  
Plasma Concentrations ◽  
Direct Proof ◽  
Brain Regions ◽  
Portal Blood ◽  
Male Rats ◽  
Unilateral Stimulation ◽  
Oxytocin Release ◽  
Hypophysial Portal ◽  
Stimulation Of

ABSTRACT The role of the paraventricular nuclei (PVN), amygdala and hippocampus in the control of the hypothalamic-pituitary-adrenal axis has been studied by determining the effect of electrical stimulation of the PVN, amygdala and hippocampus on the release of corticotrophin-releasing hormone (CRF-41) and arginine vasopressin (AVP) into hypophysial portal blood and ACTH and corticosterone into peripheral blood. Adult female Wistar rats were anaesthetized with sodium pentobarbitone and stimulation was carried out through previously implanted bipolar, glass-insulated platinum electrodes. Hypophysial portal blood was collected 30 min before and 30 min during the application of the stimulus which consisted of trains (30 s on and 30 s off) of biphasic rectangular pulses with a frequency of 50 Hz, pulse width 1 ms and amplitude 1 mA. Bilateral stimulation of the PVN increased while unilateral stimulation of the amygdala decreased the release of CRF-41 into hypophysial portal blood. The threefold increase in release of CRF-41 induced by PVN stimulation correlated with a marked increase in peripheral plasma concentrations of ACTH and corticosterone. Stimulation of the hippocampus had no significant effect on CRF-41 release, and stimulation of each of the three brain regions had no effect on AVP release into portal blood. These findings were extended in a second study to compare the effects of unilateral bipolar electrical stimulation of the PVN and of the supraoptic nucleus (SON) on the release of CRF-41, AVP and oxytocin. This study was carried out on adult male rats, anaesthetized with sodium pentobarbitone, in which the stimulus was applied through previously implanted concentric stainless-steel electrodes. Unilateral stimulation of the PVN resulted in a significant increase in the release of CRF-41 and a massive increase in oxytocin release into portal blood. Increased release of oxytocin also occurred after unilateral stimulation of the SON, but CRF-41 secretion was unaffected. The secretion of AVP was unaffected by electrical stimulation of either the SON or PVN. These results (i) provide the first direct proof for the fact that the PVN is the major source of CRF-41 in hypophysial portal blood, and (ii) suggest that the release of CRF-41 may be inhibited by the amygdala. Journal of Endocrinology (1991) 129, 99–107

Effects of trenbolone acetate and testosterone on growth and on plasma concentrations of corticosterone and ACTH in rats

1990 ◽  
Vol 126 (3) ◽  
pp. 461-466 ◽  
Author(s):  
M. N. Sillence ◽  
R. G. Rodway
Keyword(s):  
Weight Gain ◽  
Growth Response ◽  
Plasma Concentrations ◽  
Female Rats ◽  
Male Rats ◽  
Adrenal Weight ◽  
Trenbolone Acetate ◽  
Male And Female Rats ◽  
Age Related ◽  
Old Rats

ABSTRACT The effects of trenbolone acetate (TBA) on growth and on plasma concentrations of corticosterone were examined in male and female rats. At 5 weeks of age, rats were injected with TBA (0·8 mg/kg) dissolved in peanut oil, or with oil alone, daily for 10 days. In female rats, TBA caused an increase in weight gain (20–38%), a reduction in adrenal weight (19%) and a reduction in plasma concentrations of corticosterone (55%). In contrast, TBA-treated male rats showed no significant increase in weight gain, no significant change in adrenal weight and no reduction in plasma concentrations of corticosterone. The mechanism by which adrenal activity was suppressed in TBA-treated female rats was examined and the response compared with that to testosterone. Female rats (8 weeks old) were injected daily either with oil vehicle, TBA (0·8 mg/kg) or testosterone propionate (0·8 mg/kg). Testosterone increased weight gain (24%), but the growth response to TBA treatment was significantly greater (97%). A reduction in plasma concentrations of corticosterone (45%) was again observed in response to TBA. However, testosterone increased plasma concentrations of corticosterone (52%) above those of control values. Neither androgen affected plasma concentrations of ACTH. Finally, the effects of TBA were examined in 6-week-old female rats, to characterize further the apparent age-related increase in responsiveness. The growth response of 6-week-old rats (60–74%) was intermediate between that seen in 5- and 8-week-old animals. It is concluded that part of the anabolic activity of TBA may be related to a reduction in circulating concentrations of corticosterone. The effect of TBA on corticosterone concentrations differs from that of the natural androgen, testosterone, and does not appear to be mediated by a reduction in plasma concentrations of ACTH. Journal of Endocrinology (1990) 126, 461–466

Sex- and age-dependent differences in the hormone and drinking responses to water deprivation

2020 ◽  
Vol 318 (3) ◽  
pp. R567-R578 ◽  
Author(s):  
Susana Quirós Cognuck ◽  
Wagner L. Reis ◽  
Marcia S. Silva ◽  
Gislaine Almeida-Pereira ◽  
Lucas K. Debarba ◽  
...  
Keyword(s):  
Water Deprivation ◽  
Plasma Concentrations ◽  
Female Rats ◽  
Male Rats ◽  
Ang Ii ◽  
Adult Males ◽  
Adaptive Responses ◽  
Male And Female ◽  
Male And Female Rats ◽  
Female Wistar Rats

Maintenance of the volume and osmolality of body fluids is important, and the adaptive responses recruited to protect against osmotic stress are crucial for survival. The objective of this work was to compare the responses that occur in aging male and female rats during water deprivation. For this purpose, groups of male and female Wistar rats aged 3 mo (adults) or 18 mo (old) were submitted to water deprivation (WD) for 48 h. The water and sodium (0.15 M NaCl) intake, plasma concentrations of oxytocin (OT), arginine vasopressin (AVP), corticosterone (CORT), atrial natriuretic peptide (ANP), and angiotensin II (ANG II) were determined in hydrated and water-deprived animals. In response to WD, old male and female rats drank less water and saline than adults, and both adult and old females drank more water and saline than respective males. Dehydrated old animals displayed lower ANG II plasma concentration and CORT response compared with the respective normohydrated rats. Dehydrated adult males had higher plasma ANP and AVP as well as lower CORT concentrations than dehydrated adult females. Moreover, plasma OT and CORT levels of old female rats were higher than those in the dehydrated old male rats. Relative expression of ANG II type 1 receptor mRNA was decreased in the subfornical organ of adult and old male rats as well as adult female rats in response to WD. In conclusion, the study elucidated the effect of sex and age on responses induced by WD, altering the degree of dehydration induced by 48 h of WD.

EFFECT OF α-MELANOCYTE-STIMULATING HORMONE AND OVARIAN STEROIDS ON PREPUTIAL GLAND FUNCTION IN THE FEMALE RAT

1981 ◽  
Vol 90 (1) ◽  
pp. 53-58 ◽  
Author(s):  
S. M. DONOHOE ◽  
A. J. THODY ◽  
S. SHUSTER
Keyword(s):  
Pituitary Hormones ◽  
Female Rats ◽  
Male Rats ◽  
Female Rat ◽  
Preputial Gland ◽  
Melanocyte Stimulating Hormone ◽  
Experienced Male ◽  
Hypophysectomized Rats ◽  
Gland Function ◽  
Preputial Glands

Sexually experienced male rats were used to test the attractiveness of preputial gland odours of female rats. The male rats showed a clear preference for the preputial gland odours of hypophysectomized females given oestradiol benzoate (OB) for 3 or 8 days to those of control rats. Progesterone treatment had no effect on the attractiveness of the preputial gland odours of OB-treated hypophysectomized female rats. Administration of α-MSH for either 3 or 8 days, on the other hand, increased the attractiveness to male rats of preputial gland odours of OB-treated hypophysectomized females and the presence of progesterone produced no further change. When administered alone α-MSH had no effect on the attractiveness of the preputial gland odours. Other pituitary hormones, such as ACTH and prolactin, had no effect on the attractiveness of preputial gland odours of OB-treated hypophysectomized rats when administered for 3[unk]days. An increase in preputial gland size was only seen when OB, progesterone and α-MSH were administered together. It would appear that no relationship exists between the size of the preputial glands and their ability to attract male rats. It is concluded that, while α-MSH and progesterone may be important in controlling growth of the preputial glands, an interaction between α-MSH and oestrogen is more important for regulating the production of sex attractants by the preputial glands.

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