In vitro Morphometric and Proliferative Variations in VIP-Immunoreactive Pituitary Cells Induced by Estradiol

Abstract

Using double labelling for proliferating cell nuclear antigen (PCNA) and vasoactive intestinal peptide (VIP), a study was conducted to elucidate the repercussions of the addition of estradiol to monolayer pituitary cultures on the morphology, size, number, mitotic index and PCNA labelling index of VIP-immunoreactive cells, comparing the results with those obtained in control cultures. The addition of estradiol (100 nM) over 3 h of incubation led to a significant increase (p < 0.01) in the cellular, cytoplasmic and nuclear areas of VIP-immunoreactive cells and in the number of these cells. The same treatment elicited an even greater increase in the mitotic index (p < 0.01) and PCNA labelling index (p < 0.01) of VIP-immunoreactive cells. The results obtained suggest that estrogens induce proliferation and hyperplasia of in vitro VIP-immunoreactive pituitary cells.

Decreases in the Size and Proliferation Rate of VIP-lmmunoreactive Cells Induced in vitro by Testosterone Are Associated with Decreases in VIP Release

“…Our study dem onstrates that in vitro inhibition of VIP release is accom panied by in vitro inhibition by testosterone of the size, percentage and proliferation rate of pituitary VIP-immu noreactive cells. Such effects are opposite to those ob served previously in our laboratory after in vitro treat ment with estradiol [6].…”

“…Although modifications in the VIP contents of the pituitary gland after estradiol treatment [3][4][5] and the stimulatory effects of estradiol on the cellular activity and in vitro proliferation of pituitary VIP-immunoreactive cells have previously been reported by our team [6], the effects of androgens are not well known. Neonatal androgenization induces an increase in VIP levels in the pitu itary gland [7]; however, treatment of both sexes with tes tosterone decreases the release and pituitary contents of the peptide [1], As far as we are aware, no studies have been carried out in pituitary monolayer cultures to evaluate the size and the proliferation rate of VIP-immunoreactive cells or the release of the peptide in combined studies after treatment with testosterone.…”

Calcitonin is expressed in gonadotropes of the anterior pituitary gland: its possible role in paracrine regulation of lactotrope function

“…The evidence suggests that signals provided by gonadal or neuroendocrine hormones to their target AP cells may be amplified or modulated by paracrine/autocrine factors. For example, pituitaryderived vasoactive intestinal polypeptide (VIP) and galanin stimulate PRL secretion and also induce lactotrope proliferation (Kaplan et al 1988, Hsu et al 1990, Wynik et al 1993, Carretero et al 1995, Balsa et al 1996.…”

In vitro immunoblockade of VIP inhibits the proliferation of pituitary prolactin cells

“…Many studies carried out both in vivo and in vitro at our laboratory have shown that hypophyseal VIP and prolactin are modulated in a very similar way by peripheral hormones and by hypothalamic neurotransmitters (Carretero et al 1994(Carretero et al , 1995a(Carretero et al , 1996(Carretero et al , 1997a(Carretero et al , 1998.…”

“…In vitro, VIP and prolactin respond in the same way to peripheral or central regulating agents, such as dopamine or estradiol (Carretero et al 1994(Carretero et al , 1995a(Carretero et al , 1996(Carretero et al , 1997a(Carretero et al , 1998. This suggests that VIP could be involved in the regulatory axis of prolactin secretion, in concordance with the effects of the regulatory agents.…”