Induction of vasoactive intestinal peptide gene expression and prolactin secretion by insulin-like growth factor I in rat pituitary cells: evidence for an autoparacrine regulatory system.
The effects of recombinant human insulin-like growth factor I (IGF-I) on both vasoactive intestinal peptide (VIP) and PRL production and gene expression were studied using rat anterior pituitary cell cultures grown in serum-free defined medium. We also examined whether pituitary VIP could be involved in the PRL response to IGF-I and hence in a paracrine regulatory system. Exposure of cultured anterior pituitary cells to IGF-I (2.6 nM) for 3 h caused a significant decrease in both VIP content and media PRL. Treatment with IGF-I (from 0.65-5.2 nM) for 48 h increased VIP production and VIP messenger RNA (mRNA) accumulation, whereas only an increase in media and intracellular PRL content without changes in mRNA was observed. In all these experiments, IGF-I led to a decrease in both GH secretion and expression. Immunoglobulins G purified from VIP antiserum inhibited IGF-I-induced PRL release without affecting intracellular and mRNA levels. The inhibition of both GH secretion and gene expression induced by IGF-I was not blocked by VIP antiserum. In conclusion, these results indicate that IGF-I induces VIP gene expression, and its secretion and also increases PRL secretion. The effect of IGF-I on PRL release is specifically mediated by VIP through a paracrine or autocrine mechanism.
Lara
J I
JI
Servicio de Endocrinología, Fundación Jiménez Diaz, Madrid, Spain.
Lorenzo
M J
MJ
Cacicedo
L
L
Tolón
R M
RM
Balsa
J A
JA
López-Fernández
J
J
Sánchez-Franco
F
F
D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression / Q000187:drug effects*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008297:Male; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000187:drug effects* / Q000503:physiopathology; D011388:Prolactin / Q000096:biosynthesis / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014660:Vasoactive Intestinal Peptide / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology
D014660:Vasoactive Intestinal Peptide; D007334:Insulin-Like Growth Factor I; D011388:Prolactin