Stimulation of release of growth hormone from the anterior pituitary by alpha-melanocyte-stimulating hormone: a possible mechanism for induction of pseudopregnancy in the rat.
In hypophysectomized rats on day 1 of dioestrus, as well as on day 4 of pseudopregnancy, alpha-MSH (continuous infusion of 1 microgram/h) failed to maintain serum concentrations of progesterone. On the other hand, alpha-MSH did not modify the increase induced by ACTH (1 microgram/microliter as an infusion plus two additional daily injections of 30 micrograms/microliter), prolactin (200 micrograms/0.2 ml at 12-h intervals) or GH (300 micrograms/0.2 ml twice daily) on serum concentrations of progesterone in such rats. However, in intact rats alpha-MSH caused a significant rise in serum concentrations of GH on day 1 and day 2 of dioestrus. Continuous infusion of alpha-MSH produced an increase in serum concentrations of GH at 12.00 and 14.00 h on day 1 of dioestrus and at 07.00 h on day 2. It is therefore suggested that alpha-MSH may exert its effect by facilitating the secretion of GH, which in turn may induce the release of progesterone.
Volosin
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Instituto de Investigación Médica Mercedes y Martín Ferreyra, Córdoba, Argentina.
Celis
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ME
D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000818:Animals; D004031:Diestrus / Q000502:physiology; D005260:Female; D013006:Growth Hormone / Q000378:metabolism* / Q000494:pharmacology; D007016:Hypophysectomy; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011374:Progesterone / Q000097:blood; D011388:Prolactin / Q000494:pharmacology; D011555:Pseudopregnancy / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D000521:alpha-MSH / Q000494:pharmacology*
D011374:Progesterone; D000521:alpha-MSH; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D013006:Growth Hormone