Role of Angiotensin on Paracrine Prolactin Release in the Pituitary Gland and Its Possible Effects on Ovarian Function

Abstract

The present study was undertaken to investigate the role of angiotensin II (All) in GnRH-induced PRL release on the paracrine interaction among anterior pituitary cells of young male rats. A 20-min perifusion with 100 nM GnRH increased PRL release (p < 0.01) from pituitary cell aggregates, and GnRH-stimulated release of PRL was significantly suppressed by saralasin, a specific AH antagonist. The release of AI from pituitary cell aggregates was significantly (p < 0.01) increased by GnRH. These data demonstrate that GnRH is capable of stimulating PRL release through a mechanism that may involve the release of angiotensin. It was also speculated that some factors released from pituitary cells such as angiotensin might be involved in the control of ovarian functions. As an approach to investigate this possibility, porcine anterior pituitary cells and ovarian granulosa cells were co-cultured on type 1 collagen membrane which permits the exchange of the substance with molecular weights less than 9,000. The growth and progesterone production of the granulosa cells co-cultured with pituitary cells were significantly (p < 0.05) greater than those of the cells cultured in monolayer fashion. Thus, the results of the present study revealed the biological significances of the paracrine system involving angiotensin between gonadotroph and lactotroph in pituitary cells and the direct effect of the factors derived from pituitary cells on ovarian functions.

Angiotensin II Changes Inositol-1,4,5-Trisphosphate Content in the Pituitary and Hypothalamus but Not in Cerebral Cortex of the Rat Brain

“…Angll is involved in prolactin (PRL), luteiniz ing hormone (LH) and adrenocorticotropic hormone (ACTH) release from the anterior pituitary [4], However, evidence has recently been presented that Angll may also affect the regulation of pituitary hormone secretion at the hypothalamic level [4][5][6][7][8][9][10]. For example, this peptide not only affects LH and PRL release at the pituitary level, but also acts through norepinephrine (LH) and dopamine (PRL) on the hypothalamus [11,12], All the observations support the hypothesis that Angll plays an important role in regulating the hypothalamic-pituitary axis.…”