Effects of Melatonin and Natural and Synthetic Analogues of Arginine Vasotocin on Plasma Prolactin Levels in Adult Male Rats

1978 ◽  
Vol 9 (4) ◽  
pp. 236-246 ◽  
Author(s):  
Mary K. Vaughan ◽  
John C. Little ◽  
Linda Y. Johnson ◽  
David E. Blask ◽  
George M. Vaughan ◽  
...  
Keyword(s):  
Adult Male ◽  
Arginine Vasotocin ◽  
Male Rats ◽  
Plasma Prolactin ◽  
Synthetic Analogues ◽  
Natural And Synthetic

PROLACTIN STIMULATION TEST WITH PERPHENAZINE: AN EVALUATION OF PLASMA PROLACTIN LEVELS AND PITUITARY SECRETORY ACTIVITY IN THE RAT

1976 ◽  
Vol 68 (3) ◽  
pp. 355-368 ◽  
Author(s):  
A. A. VAN DER GUGTEN ◽  
P. C. SAHULEKA ◽  
G. H. VAN GALEN ◽  
H. G. KWA
Keyword(s):  
Adult Male ◽  
Secretory Activity ◽  
Female Rats ◽  
Male Rats ◽  
Plasma Prolactin ◽  
Prolactin Release ◽  
Oestrogen Treatment ◽  
Endocrine Status ◽  
Pituitary Prolactin ◽  
Single Plasma

SUMMARY Many investigations of the regulation of prolactin synthesis and release are based on single plasma prolactin determinations. The purpose of the present experiment was to ascertain whether groups of rats (i.e. young or adult, male or female animals, being either intact, gonadectomized or gonadectomized and treated with oestrone), differing in age and/or endocrine status, will react to a single dose of perphenazine by an acute release of pituitary prolactin in proportion to their initial plasma prolactin levels. No consistent relation existed between the classification of the twelve groups of rats into three categories of basal plasma prolactin levels (i.e. < 20, 25–50, > 125 ng/ml) and their response to perphenazine. Even though all groups showed a highly significant increase of plasma prolactin levels the magnitude of the maximum prolactin response at 30 min varied greatly within the groups of one category and thus was not related to the initial prolactin levels. The effect of 14 days of oestrone treatment in increasing plasma prolactin levels in gonadectomized animals was greatest in young and adult male rats, less in young females and not significant in adult females. The results obtained after perphenazine treatment in the latter group made it clear that the effect of oestrogen treatment on prolactin release can be completely blocked by increasing synthesis and/or release of the prolactin-release inhibiting factor (PIF). Since perphenazine induces decrease of pituitary prolactin and a concomitant increase of plasma prolactin levels through lowered PIF-action, the positive effect of oestrogens on prolactin release (as observed in gonadectomized male and young female rats) apparently is caused by a different mode of action. The implications of these findings for the regulation of prolactin release, as affected by the endocrine status of the rat, is discussed. Moreover, comparison of prolactin lost from the pituitary and gained in the circulation of the experimental animals, with amounts of prolactin that were observed to disappear from plasma during the experiment, provided suggestive evidence that the capacity to synthesize and/or eliminate prolactin, after a sudden provoked release of the hormone, differed among the groups. The rates of synthesis by the pituitary, of release from the pituitary into the circulation as well as of elimination of the hormone from the circulation (equally involved in determining actual plasma levels) are thought, therefore, to be far more important for the elucidation of prolactin regulation than single plasma prolactin determinations.

Increased dopaminergic inhibition of prolactin in the hypoprolactinaemic IPL nude rat

1985 ◽  
Vol 107 (3) ◽  
pp. 325-329 ◽  
Author(s):  
H. Cohen ◽  
I. Sabbagh ◽  
P. Guillaumot ◽  
J. Bertrand
Keyword(s):  
Adult Male ◽  
Physiological Saline ◽  
Prolactin Secretion ◽  
Male Rats ◽  
Saline Control ◽  
Plasma Prolactin ◽  
Synthesis Inhibitor ◽  
Nude Rat ◽  
Prolactin Content ◽  
Pituitary Prolactin

ABSTRACT In this study, aimed at investigating whether dopaminergic regulation of prolactin could be implicated in the hypoprolactinaemia observed in the IPL nude rat, dopaminergic inhibition of prolactin was suppressed using a catecholamine synthesis inhibitor α-methyltyrosine (MT) and a dopaminergic antagonist sulpiride. Adult male rats (IPL nude and normal) were injected through implanted atrial cannulae with either MT (250 mg/kg) or physiological saline (control). Rats were decapitated 2 h after the injection. Plasma prolactin levels, compared with basal values, increased by 15·6 ± 1·9 (s.e.m.)- and 5·89 ± 0·6-fold in IPL nude and normal rats respectively. This difference was highly significant. The pituitary prolactin content was decreased in both groups. In a second experiment, adult male IPL nude or normal rats were injected with either sulpiride (1 mg/kg) or saline and decapitated 2, 4, 8, 12, 14 and 24 h later. Plasma prolactin levels, compared with basal values, were increased in rats injected with sulpiride by 9·2 ± 1·8 and 3·4 ± 0·7-fold in IPL nude and normal rats respectively. The pituitary prolactin content was reduced more in IPL nude than in normal sulpiride-injected rats. These data suggest that prolactin secretion, as well as synthesis, is under an increased dopaminergic inhibition in the male IPL nude rat. J. Endocr. (1985) 107, 325–329

FAILURE OF SODIUM LOADING OR DEFICIENCY TO AFFECT PLASMA PROLACTIN IN THE MALE RAT

1977 ◽  
Vol 86 (2) ◽  
pp. 299-305 ◽  
Author(s):  
J. A. M. Mattheij
Keyword(s):  
Adult Male ◽  
Plasma Aldosterone ◽  
Male Rats ◽  
Male Rat ◽  
Sodium Balance ◽  
Plasma Prolactin ◽  
Deficient Diet ◽  
Marked Rise ◽  
Sodium Metabolism ◽  
Plasma Prl

ABSTRACT The relation between plasma prolactin (PRL) and sodium metabolism was studied in adult male rats. During the experiments attention was given to the avoidance of stress. Cannulated rats were infused with 2.5 ml 5 % NaCl over a 40 min period. Plasma PRL did not change during or up to 2 h after this infusion. Other rats were subjected to a sodium deficient diet for 3 weeks. This treatment which induced a marked rise in plasma aldosterone, did not cause a change in plasma PRL. It is concluded that PRL does not have an important role in the regulation of sodium balance.

ASSAY OF CORTICOTROPHIN PREDNISOLONE PRETREATMENT INSTEAD OF HYPOPHYSECTOMY IN THE ADRENAL ASCORBIC ACID DEPLETION TEST

1960 ◽  
Vol XXXV (IV) ◽  
pp. 594-603 ◽  
Author(s):  
Christian Hamburger
Keyword(s):  
Ascorbic Acid ◽  
Adult Male ◽  
Subcutaneous Injection ◽  
Aqueous Suspension ◽  
Inhibitory Effect ◽  
Male Rats ◽  
Synthetic Analogues ◽  
Single Subcutaneous Injection ◽  
Calibration Curves ◽  
Intact Rats

ABSTRACT The inhibitory effect of various corticosteroids and synthetic analogues on the stress-induced release of corticotrophin was measured in adult male rats by means of the adrenal ascorbic acid depletion test. All the compounds examined were active, dexamethasone and prednisolone being the most effective inhibitors. A single subcutaneous injection of a microcrystalline aqueous suspension of prednisolone (1.5 mg per rat), given about 2 hours before left-sided adrenalectomy, blocked completely the adrenal ascorbic acid depletion. Quantitative assays of a purified corticotrophin preparation were carried out with hypophysectomized and prednisolone-treated intact rats. The latter were less sensitive to corticotrophin, but the slopes of the calibration curves and the standard deviations appeared to be the same in both instances. It is concluded that it is feasible to replace the surgical hypophysectomy by prednisolone pretreatment in the ascorbic acid depletion test for corticotrophin.

VASOTOCIN BIOSYNTHESIS BY CULTURED PINEAL GLANDS FROM ADULT MALE RATS

1978 ◽  
Vol 77 (1) ◽  
pp. 147-148 ◽  
Author(s):  
S. PAVEL ◽  
ELENA GHINEA ◽  
R. GOLDSTEIN ◽  
V. MATULEVIČIUS
Keyword(s):  
Pineal Gland ◽  
Adult Male ◽  
Marked Reduction ◽  
Subcommissural Organ ◽  
Parenchymal Cell ◽  
Arginine Vasotocin ◽  
Male Rats ◽  
Ependymal Cells ◽  
Cell Type ◽  
Predominant Cell Type

Institute of Endocrinology, Bucharest, Romania (Received 20 September 1977) We have previously reported that the pineal gland of the mammalian foetus, which comprises mainly specialized secretory ependymal cells (Anderson, 1965), synthesizes the nonapeptide arginine-vasotocin (AVT; Pavel, Dorcescu, Petrescu-Holban & Ghinea, 1973; Pavel, Goldstein, Ghinea & Calb, 1977). However, in contrast with the foetal pineal gland, the predominant cell type in the pineal gland of the adult mammal is the parenchymal cell or pinealocyte (Quay, 1965); there is a marked reduction in the number of ependymal cells and they are restricted to the pineal recess (Anderson, 1965), which shows the same secretory characteristics as the subcommissural organ (Palkovits, 1965). Since we have postulated the ependymal origin of mammalian AVT (Pavel, 1971; Pavel et al. 1973; Pavel, 1975; Pavel et al. 1977), it seemed worthwhile to investigate the synthesis of AVT in the adult pineal gland in order to elucidate, if only

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