Sex differences in vasoactive intestinal peptide (VIP) concentrations in the anterior pituitary and hypothalamus of rats.
Recent evidence suggests that vasoactive intestinal peptide (VIP), a putative prolactin (PRL)-releasing factor, is both synthesized and released by anterior pituitary cells, to act as a paracrine or autocrine factor. We have investigated the hypothesis that hypothalamic or pituitary VIP levels differ in male and female rats, since neuroendocrine control of PRL is sexually differentiated. Opposite sex differences were found in the hypothalamus and anterior pituitary. Random-cycle female rats had one-third higher VIP levels in the hypothalamus than males. In contrast, anterior pituitary VIP levels were 3 times as high in male rats as in females. Median eminence VIP levels were similarly low in both sexes. These results support a possible role of VIP in the sexually dimorphic regulatory mechanisms of PRL secretion. Moreover, demonstration that hypothalamic and pituitary VIP levels vary in opposite directions suggests that VIP is differentially regulated at the two sites.
Riskind
P N
PN
Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston 02114.
Allen
J M
JM
Gabriel
S M
SM
Koenig
J I
JI
Audet-Arnold
J
J
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D005260:Female; D007031:Hypothalamus / Q000378:metabolism*; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D008297:Male; D008473:Median Eminence / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D012737:Sex Factors; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism*
D007457:Iodine Radioisotopes; D014660:Vasoactive Intestinal Peptide