Involvement of the neurointermediate lobe of the pituitary gland in the secretion of prolactin and luteinizing hormone in the rat.
The relationship between prolactin (PRL) secretion and the neurointermediate lobe (NIL) of the pituitary gland was investigated. Plasma PRL concentrations in rats bearing anterior pituitaries autografted with or without the NIL to the renal capsule were elevated to equal extents at 1 through 6 weeks after surgery (p greater than 0.10). PRL levels in ovariectomized rats in which the NIl had been removed surgically (NIL-X) or only visualized (NIL-C) were 3-7 ng/ml 4, 7, and 28 days after surgery (p greater than 0.10); however, they were slightly higher in NIL-X vs. NIL-C rats 14 days after surgery (p less than 0.05). Plasma luteinizing hormone (LH) concentrations in NIL-C rats increased by 36% from 2 to 4 weeks after surgery (p less than 0.5); this increase was not detected in NIL-X rats. PRL and LH surges were induced by estradiol implants in ovariectomized NIL-X and NIL-C rats; the profiles of the PRL surges were superimposable, although the magnitude of the LH surge was only 50% that in NIL-C rats (p less than 0.5). These results cast doubt on the importance of the NIL in the regulation of PRL secretion either via secreting hypophysiotropic hormones or via conducting anterior pituitary hormones directly to the median eminence. However, the NIL may have a physiologically important role in the regulation of LH secretion.
D000818:Animals; D002369:Castration; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D007986:Luteinizing Hormone / Q000378:metabolism*; D010902:Pituitary Gland / Q000502:physiology*; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D004958:Estradiol; D011388:Prolactin; D007986:Luteinizing Hormone