Differential effects of in vivo estrogen administration on hypothalamic growth hormone releasing hormone and somatostatin gene expression.
The aim of this study was to investigate the effect of in vivo estrogen administration on hypothalamic growth hormone releasing hormone (GHRH) and somatostatin (SS) gene expression. We found that estrogen administration (estradiol valerate 250 micrograms/every 3 days, subcutaneously) to male rats induced a decrease in both hypothalamic GHRH mRNA levels and GHRH content, that was significant after 3 and 8 days of treatment. In contrast SS mRNA levels were transiently elevated after 1 and 3 days of estrogen administration, returning to normal values after 8 days of treatment. These data suggest that the existence of sexual dimorphism in GH secretion in the rat could be mediated to some extent by gonadal hormones regulating somatostatin and GHRH gene expression in the hypothalamus.
Señaris
R M
RM
Department of Physiology, Faculty of Medicine, University of Santiago, Santiago de Compostela, Spain.
Lago
F
F
Lewis
M D
MD
Dominguez
F
F
Scanlon
M F
MF
Dieguez
C
C
D000818:Animals; D004967:Estrogens / Q000494:pharmacology*; D005786:Gene Expression Regulation; D013007:Growth Hormone-Releasing Hormone / Q000096:biosynthesis / Q000235:genetics*; D007028:Hypothalamic Hormones / Q000096:biosynthesis / Q000235:genetics*; D066298:In Vitro Techniques; D008297:Male; D012333:RNA, Messenger / Q000096:biosynthesis; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D012727:Sex Characteristics; D013004:Somatostatin / Q000096:biosynthesis / Q000235:genetics*
D004967:Estrogens; D007028:Hypothalamic Hormones; D012333:RNA, Messenger; D013004:Somatostatin; D013007:Growth Hormone-Releasing Hormone