Differential regulation of gonadotropins and glycoprotein hormone alpha-subunit by IGF-I in anterior pituitary cells from male rats.
IGF-I has been demonstrated to stimulate basal and GnRH-induced gonadotropin release. IGF-I also elicites alpha-subunit secretion in human pituitary tumor cells. The aims of this study were to evaluate both the effect of IGF-I on gonadotropin LH-beta and FSH-beta mRNA levels and glycoprotein alpha-subunit gene expression in cultured rat anterior pituitary cells. The exposure of pituitary cells to recombinant human IGF-I (rhlGF-I; 2 microg/ml) for 72 h markedly stimulated basal LH and FSH release whereas their mRNA levels remained unmodified. IGF-I elicited a-subunit release from pituitary cells (p < 0.01) and augmented its mRNA levels. Exposure to IGF-I consistently reduced GH release from pituitary cells. This study shows that the gonadotropin-releasing effects of IGF-I are not paralleled by changes in their mRNAs whereas IGF-I stimulates not only alpha-subunit release but also its mRNA levels. This study provides the first observation of alpha-subunit regulation by IGF-I in normal pituitary cells, where a differential regulation between release and synthesis for gonadotropin a-and 1-subunits is also shown.
Pazos
F
F
Servicio de Endocrinologia, Hospital Ramón y Cajal, Madrid, Spain.
Sánchez-Franco
F
F
Balsa
J
J
Escalada
J
J
Cacicedo
L
L
D000818:Animals; D018929:Cell Culture Techniques; D037201:Follicle Stimulating Hormone, beta Subunit / Q000096:biosynthesis*; D005786:Gene Expression Regulation / Q000187:drug effects; D015292:Glycoprotein Hormones, alpha Subunit / Q000096:biosynthesis*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D037101:Luteinizing Hormone, beta Subunit / Q000096:biosynthesis*; D008297:Male; D010902:Pituitary Gland / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar
D037201:Follicle Stimulating Hormone, beta Subunit; D015292:Glycoprotein Hormones, alpha Subunit; D037101:Luteinizing Hormone, beta Subunit; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I