The effect of the estrous cycle and estrogen on the release of immunoreactive alpha-melanocyte-stimulating hormone.
Circulating levels and tissue content of alpha-MSH were measured on the morning of various days of the estrous cycle, and on the afternoon of proestrus in freely moving conscious rats. No surges of alpha-MSH were detected by RIA in the morning of various days of the cycle. The neurointermediate lobe content of alpha-MSH was slightly elevated on diestrus 1 as compared to the levels on diestrus 11 and proestrus but not to estrous levels. No changes in alpha-MSH content were detected in the anterior pituitary, the median eminence, mediobasal hypothalamus and the preoptic area at various stages of the estrous cycle. Plasma alpha-MSH levels were slightly elevated at 1500 hr of proestrus which was followed three hours later by a decline. This profile of plasma alpha-MSH on the afternoon of proestrus was reproduced by the SC administration of estradiol benzoate to long-term ovariectomized rats. These data suggest that, contrary to the results obtained by bioassay of alpha-MSH no surges of alpha-MSH occur on any day of the cycle, although a slight elevation on the afternoon of proestrus was detected. The altered pattern of release of this peptide on the afternoon of proestrus may be induced by estrogen.
D000818:Animals; D004958:Estradiol / Q000494:pharmacology*; D004971:Estrus; D005260:Female; D007033:Hypothalamus, Middle / Q000378:metabolism; D007986:Luteinizing Hormone / Q000097:blood; D008473:Median Eminence / Q000378:metabolism; D009074:Melanocyte-Stimulating Hormones / Q000097:blood / Q000378:metabolism*; D010052:Ovariectomy; D010902:Pituitary Gland / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D011301:Preoptic Area / Q000378:metabolism; D011388:Prolactin / Q000097:blood; D051381:Rats; D013493:Suprachiasmatic Nucleus / Q000378:metabolism
D004958:Estradiol; D011388:Prolactin; D007986:Luteinizing Hormone; D009074:Melanocyte-Stimulating Hormones