Abstract: 70

EFFECTS OF HYPERPROLACTINEMIA ON ALDOSTERONE SECRETION IN OVARIECTOMIZED RATS.

MM Kau^{1 2} , JJ Chen^{1 *}, MJ Lo¹ , LL Chang³ , SF Kan¹ , JL Wang¹ , PS Wang^{1 *}
Dept. Physiol., Natl. Yang-Ming Univ., Taipei, Taiwan, ROC. ¹
Natl. Taipei Coll. Nursing, Taipei, Taiwan, ROC. ²
Dept. Chem. Eng., Chin. Cult. Univ., Taipei, Taiwan, ROC. ³

Hypogonadism, amenorrhea, higher blood pressure and renin-angiotensin responsiveness have been shown in hyperprolactinemic patients. The present study was to evaluate the mechanisms of hyperprolactinemia on aldosterone secretion in ovariectomized (Ovx) rats. Hyperprolactinemia was induced by transplantation of rat anterior pituitary glands (APs) under kidney capsule for six weeks in female rats. Control rats were transplanted with cerebral cortex (CX). Four weeks later, rats were Ovx for two weeks before decapitation. Plasma prolactin and aldosterone in rats increased by AP-transplantation. In the in vitro study, the basal, angiotensin II (Ang II)-, KCl-, and adrenocorticotropic hormone (ACTH)- stimulated aldosterone secretion by adrenal zona glomerulosa (ZG) cells were higher in AP-grafted than in CX-grafted rats. AP-grafted rats had greater responses of aldosterone secretion to forskolin, 8-bromo-adenosine 3':5'-cyclic monophosphate (8-Br-cAMP), nifedipine and tetrandrine than in CX-grafted group. However, there was no difference in the conversion of 25- OH-cholesterol to pregnenolone or the expression of desmolase (P450_scc) in ZG cells between AP-grafted and CX-grafted rats. The conversion of corticosterone into aldosterone and the expression of steroidogenic acute regulatory (StAR) protein in ZG cells were greater in AP-grafted than in CX-grafted rats. These results suggest that hyperprolactinemia increases the basal, Ang II-, KCl-, and ACTH-stimulated aldosterone secretion by ZG cells in Ovx rats through activation of adenylyl cyclase, L- and T-type Ca²⁺ channels, post-cAMP pathway, and aldosterone synthase as well as the increased expression of StAR protein in ZG cells.

    This abstract is being presented on Sunday, August 1 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.