Somatostatin-28(1–12)-Like Immunoreactive Substance Is Secreted into Hypophysial Portal Vessel Blood in the Rat

1984 ◽  
Vol 38 (1) ◽  
pp. 88-90 ◽  
Author(s):  
John Sheward ◽  
Robert Benoit ◽  
George Fink
Keyword(s):  
Portal Vessel ◽  
Hypophysial Portal

Hypophysial Portal Vessel Infusion:In VivoDemonstration of LRF, FRF, and PIF in Pituitary Stalk Plasma12

Endocrinology ◽  
1971 ◽  
Vol 89 (4) ◽  
pp. 1042-1046 ◽  
Author(s):  
IBRAHIM A. KAMBERI ◽  
RENON S. MICAL ◽  
JOHN C. PORTER
Keyword(s):  
Pituitary Stalk ◽  
Portal Vessel ◽  
Hypophysial Portal

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

Effect of Synthetic LRF Infused into a Hypophysial Portal Vessel on Gonadotropin Release1

Endocrinology ◽  
1973 ◽  
Vol 93 (1) ◽  
pp. 205-209 ◽  
Author(s):  
JEROME G. ONDO ◽  
ROBERT L. ESKAY ◽  
RENON S. MICAL ◽  
JOHN C. PORTER
Keyword(s):  
Portal Vessel ◽  
Hypophysial Portal

Levels of LH-releasing hormone in hypophysial stalk plasma during an oestrogen-stimulated surge of LH in ovariectomized rats

1987 ◽  
Vol 112 (3) ◽  
pp. 351-359 ◽  
Author(s):  
W. J. de Greef ◽  
J. de Koning ◽  
A. M. I. Tijssen ◽  
B. Karels
Keyword(s):  
Jugular Vein ◽  
Ovariectomized Rats ◽  
In Vitro Bioassay ◽  
Portal Vessel ◽  
Oestradiol Benzoate ◽  
Portal Plasma ◽  
Endogenous Release ◽  
Lh Releasing Hormone ◽  
Hypophysial Portal

ABSTRACT Treatment of ovariectomized rats with 50 μg oestradiol benzoate, followed by 20 μg oestradiol benzoate 3 days later, induced surges of LH and FSH on the day following the second injection with oestradiol benzoate. During this surge of gonadotrophins, which was not blocked by the anaesthetic required to collect hypophysial stalk blood, increased hypophysial stalk plasma levels of immunoreactive LHRH were noted. Furthermore, the levels of LHRH in hypophysial portal blood were found to fluctuate. Measurement of LHRH in a pool of portal plasma revealed similar results when determined by radioimmunoassay and by a sensitive in-vitro bioassay. To mimic the observed release of LHRH during the surge of gonadotrophins, LHRH was infused, either systemically or directly into a long portal vessel, into oestrogen-treated, ovariectomized rats which had their endogenous release of LHRH blocked by pentobarbitone. An infusion of LHRH into the jugular vein, resulting in peripheral levels of LHRH which were somewhat lower than those measured in hypophysial stalk plasma, caused a surge of FSH similar to that found in rats used for collection of hypophysial stalk blood. When compared with the values in the latter animals, however, the levels of LH became two to four times higher by this infusion of LHRH. When LHRH was infused directly into a long portal vessel to mimic the observed secretion rate of LHRH during the oestrogen-stimulated surge of gonadotrophins, then the surges of LH and FSH were lower than those observed in the rats used for collection of stalk blood. J. Endocr. (1987) 112, 351–359

THE RESPONSIVENESS OF THE ANTERIOR PITUITARY GLAND TO LUTEINIZING HORMONE RELEASING FACTOR IN RATS EXPOSED TO CONSTANT LIGHT

1975 ◽  
Vol 65 (3) ◽  
pp. 439-445 ◽  
Author(s):  
G. FINK
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Anterior Pituitary Gland ◽  
Constant Light ◽  
Blood Samples ◽  
Portal Vessel ◽  
Readily Releasable Pool ◽  
The Mean ◽  
Hypophysial Portal

SUMMARY The responsiveness of the anterior pituitary gland to synthetic luteinizing hormone releasing factor (LH-RF) was tested in rats exposed to constant light. At a dosage of 50 ng LH-RF/ 100 g body wt the mean maximal increments in plasma LH and FSH were similar to those at 10.00 h of pro-oestrus. The increments in the plasma gonadotrophins at dosages of 500 and 1000 ng LH-RF/100 g body wt did not differ significantly from those at 250 ng LH-RF/ 100 g body wt. These findings suggest that, in contrast to rats which exhibit regular oestrous cycles, the preovulatory (post-coital) release of LH in rats exposed to constant light may depend almost entirely on the release of a relatively large amount of LH-RF into hypophysial portal vessel blood. Whereas in pro-oestrous animals a relatively small fraction of the readily releasable pool of LH is released during the spontaneous preovulatory surge, in rats exposed to constant light most releasable LH appears to be discharged during the reflex preovulatory surge of this hormone. The concentrations of radioimmunoassayable FSH in blood samples withdrawn before the injection of LH-RF support the view that FSH secretion in the rat is increased by constant exposure to light.

Somatostatin-28 is an hormonally active peptide secreted into hypophysial portal vessel blood

1983 ◽  
Vol 260 (2) ◽  
pp. 334-337 ◽  
Author(s):  
R.P. Millar ◽  
W.J. Sheward ◽  
I. Wegener ◽  
G. Fink
Keyword(s):  
Portal Vessel ◽  
Active Peptide ◽  
Hypophysial Portal
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