Production and Regulation of Inhibin Subunits in Pituitary Gonadotropes

Abstract

Two related proteins, inhibin and activin, are produced and secreted by the gonads and act at the pituitary to regulate FSH secretion. In the present study, the alpha and beta B, but not the beta A, polypeptide subunits of inhibin were localized in the cytoplasm of FSH- and LH-immunoreactive (ir) gonadotropes. Ovariectomy (OVX) increased the size and number of cells immunoreactive for inhibin-alpha and -beta B as well as the mRNAs encoding these subunits. Treatment with estrogen prevented these effects. These results suggest that pituitary gonadotropes are sources, as well as targets, of inhibin-related peptides, whose expression in the pituitary is modulated by ovarian factors.

Demonstration of Activin in Normal Pituitary and in Various Human Pituitary Adenomas by Immunohistochemistry.

“…The subcellular localization of activin in the present study was in accord with those reported by Roberts et al in the rat anterior pituitary [14,15]. They found inhibin a and fi immunoreactivities in cytoplasms of gonadotropes and their costorage with LH and FSH secretory granules.…”

Inhibin .ALPHA., .BETA.A and .BETA.B Subunit Messenger Ribonucleic Acid Levels in Cultured Rat Pituitary: Studies by a Quantitative RT-PCR.

“…In spite of the findings demonstrating an ubiquitous presence of a subunit mRNA in the rat pituitary [3][4][5][6][7][8], the presence and subtype of fi subunit in the rat pituitary has been controversial. So far, Meunier et al [3], Roberts et al [4] and Corrigan et al [5], and Depaolo et al [6] have all reported the fi subunit mRNA expression with a sole or a predominance of flu. Halvorson et al [9] demonstrated that NA mRNA was coexpressed with a and /3 subunits and activin type 2 receptor mRNAs in cultured rat anterior pituitary cells.…”

“…43: 403-410,1996) INHIBINS and activins are known to modulate FSH secretion from the rat anterior pituitary [1,2]. Along with their endocrine role, mainly exerted by inhibin, enough evidence has been accumulated [3][4][5][6][7] for an autocrine or a paracrine role of these peptides in FSH secretion. So far, studies demonstrating local expressions of Inhibin a and fiB subunit mRNAs [3][4][5][6][7][8], a decrease in FSH secretion by a passive immunoneutralization with activin B monoclonal antibody [5,6] or immuno-…”

“…Along with their endocrine role, mainly exerted by inhibin, enough evidence has been accumulated [3][4][5][6][7] for an autocrine or a paracrine role of these peptides in FSH secretion. So far, studies demonstrating local expressions of Inhibin a and fiB subunit mRNAs [3][4][5][6][7][8], a decrease in FSH secretion by a passive immunoneutralization with activin B monoclonal antibody [5,6] or immuno-precipitation of local secretory products by the antisera [7], have indicated that activin B is a major subtype of rat pituitary activin, but the type of inhibins, either A or B, and activins, either A, B or AB, playing a major role in FSH secretion has recently been a matter of controversy. Bilezikjian et al [7,8] and Halvorson et al [9] recently detected the presence of L A and f subunit mRNAs in the rat anterior pituitary and suggested a certain role of activin A in FSH secretion.…”

Letrozole in ovulation induction (a review)

“…Таким образом, повышается инкреция ФСГ, что приводит к росту фолликулов. Поэтому механизм отрицатель-ной обратной связи остается интактным, происхо-дит нормальный рост фолликулов, выбор доминант-ного фолликула, атрезия меньших по размеру фол-ликулов, что приводит в конечном счете к монофол-ликулярному росту и овуляции [9][10][11][12].…”