The Effect of Thyrotropin Releasing Hormone on Cell Proliferation in the Anterior Pituitary Gland of Thyroidectomized Rats

1975 ◽  
Vol 17 (1) ◽  
pp. 92-95 ◽  
Author(s):  
Jolanta Kunert-Radek ◽  
Marek Pawlikowski
Keyword(s):  
Cell Proliferation ◽  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Thyrotropin Releasing Hormone ◽  
Anterior Pituitary Gland ◽  
Releasing Hormone

THYROTROPHIN RELEASING HORMONE-INDUCED GROWTH HORMONE AND PROLACTIN RELEASE: PHYSIOLOGICAL STUDIES IN INTACT RATS AND IN HYPOPHYSECTOMIZED RATS BEARING AN ECTOPIC PITUITARY GLAND

1977 ◽  
Vol 72 (3) ◽  
pp. 301-311 ◽  
Author(s):  
A. E. PANERAI ◽  
IRIT GIL-AD ◽  
DANIELA COCCHI ◽  
V. LOCATELLI ◽  
G. L. ROSSI ◽  
...  
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Time Lapse ◽  
Anterior Pituitary Gland ◽  
Plasma Prolactin ◽  
Thyrotrophin Releasing Hormone ◽  
Releasing Hormone ◽  
Clear Cut ◽  
Urethane Anaesthesia ◽  
Releasing Effect

SUMMARY To determine how the sensitivity of the ectopic anterior pituitary gland to the GH-releasing effect of thyrotrophin releasing hormone (TRH) might be affected by the time lapse from transplantation, TRH (0·15 and 0·6 μg) was injected i.v. into hypophysectomized (hypox)-transplanted rats under urethane anaesthesia 1,3, 8,15, 30 and 60 days after transplantation, and plasma samples were taken 5 and 10 min later. Baseline GH values gradually decreased with time from about 16·0 ng/ml (1 day) to about 3·0 ng/ml (30 and 60 days). The TRH-induced GH release was absent 1 day after transplantation, present only with the higher TRH dose 3 and 8 days after transplantation, and clearly elicitable, also with the lower TRH dose (0·15 μg), from 15 up to 60 days. Determination of plasma prolactin concentrations showed a decline from about 85·0 ng/ml (1 day) to about 32·0 ng/ml (8 days); subsequently (15–60 days) prolactin values stabilized. Plasma prolactin levels increased 15 and 60 days after transplantation only when a dose of 0·6 μg TRH was given. In intact weight-matched rats, TRH induced a GH response only at the dose of 1·2 μg while a short-lived but clear-cut prolactin response could be obtained even with the 0·3 μg dose. The present results indicate that: (1) disconnexion between the central nervous system and the anterior pituitary gland greatly enhances GH responsiveness while blunting prolactin responsiveness to TRH; (2) the sensitivity of the anterior pituitary gland to the GH-releasing effect of TRH increases with time from transplantation; (3) TRH is a more effective prolactin-than GH-releaser on the pituitary gland in situ.

Prolactin release, oestrogens and proliferation of prolactin-secreting cells in the anterior pituitary gland of adult male rats

1986 ◽  
Vol 108 (3) ◽  
pp. 399-403 ◽  
Author(s):  
R. L. Pérez ◽  
G. A. Machiavelli ◽  
M. I. Romano ◽  
J. A. Burdman
Keyword(s):  
Cell Proliferation ◽  
Pituitary Gland ◽  
Adult Male ◽  
Anterior Pituitary ◽  
Pituitary Hormones ◽  
Anterior Pituitary Gland ◽  
Male Rats ◽  
Serum Prolactin ◽  
Prolactin Release ◽  
Experimental Conditions

ABSTRACT Relationships among the release of prolactin, the effect of oestrogens and the proliferation of prolactin-secreting cells were studied under several experimental conditions. Administration of sulpiride or oestradiol released prolactin and stimulated cell proliferation in the anterior pituitary gland of adult male rats. Clomiphene completely abolished the rise in cell proliferation, but did not interfere with the sulpiride-induced release of prolactin. Treatment with oestradiol plus sulpiride significantly increased serum prolactin concentrations and the mitotic index compared with the sum of the stimulation produced by both drugs separately. Bromocriptine abolished the stimulatory effect of oestradiol on the serum prolactin concentration and on cell proliferation. In oestradiol- and/or sulpiride-treated rats, 80% of the cells in mitoses were lactotrophs. The remaining 20% did not stain with antisera against any of the pituitary hormones. The number of prolactin-secreting cells in the anterior pituitary gland significantly increased after the administration of oestradiol or sulpiride. The results demonstrate that treatment with sulpiride and/or oestradiol increases the proliferation and the number of lactotrophs in the anterior pituitary gland of the rat. J. Endocr. (1986) 108, 399–403

Pituitary and testicular responses in sexually mature bulls after intravenous injections of graded doses of LH-releasing hormone

1984 ◽  
Vol 103 (3) ◽  
pp. 371-376 ◽  
Author(s):  
M. J. D'Occhio ◽  
B. P. Setchell
Keyword(s):  
Pituitary Gland ◽  
Anterior Pituitary ◽  
Anterior Pituitary Gland ◽  
Limiting Factor ◽  
Releasing Hormone ◽  
Intravenous Injections ◽  
Gonadotrophin Secretion ◽  
Lh Release ◽  
Lh Releasing Hormone ◽  
Sexually Mature

ABSTRACT The capacity of the anterior pituitary gland and testes in mature bulls (705±9 (s.e.m.) kg body wt, n = 4) to respond to graded doses of LH-releasing hormone (LHRH) was assessed relative to endogenous profiles of LH and testosterone secretion. Endogenous hormone profiles were determined by bleeding bulls at 20-min intervals for 12 h. Responses to LHRH were assessed on successive days after single intravenous injections of 1, 5, 10, 50 or 100 ng LHRH/kg body wt. Blood samples were taken at −40, −20, 0, 10, 20, 30, 40, 60 and 120 min relative to LHRH injection. During a 12-h bleed bulls showed spontaneous pulses of LH and testosterone which had peak amplitudes of 2·6±0·5 μg/l and 44·5 ± 7·1 nmol/l respectively. Respective peak LH (μg/l) and testosterone (nmol/l) responses to LVRH were as follows: 1 ng LHRH (3·0±0·7: 47·3±4·1); 5 ng LHRH (8·0±1·2; 52·8 ± 6·2); 10 ng LHRH (11·1±2·3; 57·7 ± 9·1); 50 ng LHRH (19·2±2·8; 47·9±8·6); 100 ng LHRH (19·1±4·7; 43·9 ±6·4). A dose of 1 ng LHRH/kg produced LH and testosterone responses which were comparable in amplitude to spontaneous peaks in the respective hormone. There was a linear (y = 0·28x+5·72; r = 0·81) increase in the LH response to doses of LVRH between 1 and 50 ng/kg; corresponding testosterone responses showed no relationship with the dose of LHRH. The capacity of the anterior pituitary gland to release amounts of LH eight to ten times in excess of those secreted during spontaneous peaks suggests that (1) there exists a large releasable store of LH in the anterior pituitary gland and (2) hypothalamic LHRH is a limiting factor in gonadotrophin secretion. In contrast to LH release, the androgenic response of the testes to acute gonadotrophic stimulation is determined largely by prevailing steroidogenic activity. J. Endocr. (1984) 103, 371–376

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