Gonadal steroids modulate Fas-induced apoptosis of lactotropes and somatotropes.
We have previously reported that Fas activation induces apoptosis of anterior pituitary cells from rats at proestrus but not at diestrus and in an estrogen-dependent manner. In this study, we evaluated the effect of Fas activation on apoptosis of lactotropes and somatotropes during the estrous cycle and explored the action of gonadal steroids on Fas-induced apoptosis. Also, we studied whether changes in Fas expression are involved in the apoptotic response of anterior pituitary cells. Fas activation increased the percentage of TUNEL-positive lactotropes and somatotropes at proestrus but not at diestrus. FasL triggered apoptosis of somatotropes only when cells from ovariectomized rats were cultured in the presence of 17 β-estradiol (E2). Progesterone (P4) blocked the apoptotic action of the Fas/FasL system in lactotropes and somatotropes incubated with E2. Both E2 and P4 increased the percentage of cells expressing Fas at the cell membrane. Our results show that Fas activation induces apoptosis of lactotropes and somatotropes at proestrus but not at diestrus. Gonadal steroids may be involved in the apoptotic response of lactotropes and somatotropes, suggesting that Fas activation is implicated in the renewal of these pituitary subpopulations during the estrous cycle. The effect of gonadal steroids on Fas expression may be only partially involved in regulation of the Fas/FasL apoptotic pathway in the anterior pituitary gland.
Facultad de Medicina, Instituto de Investigaciones en Reproducción, Universidad de Buenos Aires, Paraguay 2155, Buenos Aires, Argentina.
Gabriela
G
Jaita
Sandra
S
Zárate
Luciana
L
Ferrari
Daniela
D
Radl
Jimena
J
Ferraris
Guadalupe
G
Eijo
Verónica
V
Zaldivar
Daniel
D
Pisera
Adriana
A
Seilicovich
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002478:Cells, Cultured; D004958:Estradiol / Q000494:pharmacology; D030762:Estrous Cycle; D053222:Fas Ligand Protein / Q000502:physiology; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D012739:Gonadal Steroid Hormones / Q000494:pharmacology*; D020287:In Situ Nick-End Labeling; D052682:Lactotrophs / Q000166:cytology* / Q000187:drug effects; D010052:Ovariectomy; D010903:Pituitary Gland, Anterior / Q000166:cytology; D011374:Progesterone / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D052683:Somatotrophs / Q000166:cytology* / Q000187:drug effects; D019014:fas Receptor / Q000235:genetics / Q000502:physiology*
D053222:Fas Ligand Protein; D012739:Gonadal Steroid Hormones; D019014:fas Receptor; D011374:Progesterone; D004958:Estradiol