Effects of Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2) on GH, LH, prolactin, FSH, and TSH secretion in rats with and without morphine.
Plasma concentrations of GH, LH, prolactin, FSH, and TSH were evaluated in adult rats after administration of Tyr-MIF-1. Male rats were killed 0, 15, 30, and 60 min after Tyr-MIF-1 (0.02, 0.2 and 2.0 mg/kg) and ovariectomized females 15 min after injection of the peptide (0.2 and 2.0 mg/kg). The effect of Tyr-MIF-1 on pituitary hormonal secretion in morphine-treated ovariectomized rats also was studied. After 15 min, Tyr-MIF-1 (0.2 mg/kg) increased plasma concentrations of LH in males (p less than 0.05) and, at 2.0 mg/kg, in ovariectomized rats (p less than 0.05). Tyr-MIF-1 (0.2 mg/kg) decreased plasma concentrations of GH as compared with diluent at 15 min in males (p less than 0.05) but was ineffective in ovariectomized females not receiving morphine. Plasma concentrations of prolactin, FSH, and TSH remained unchanged both in males and in ovariectomized females by any of the administered doses of the peptide at any of the times tested. When administered to ovariectomized rats injected earlier with morphine sulfate, Tyr-MIF-1 (0.2 and 2.0 mg/kg) reduced (p less than 0.05) the effect of morphine (5 mg/kg) on GH secretion and tended (p = 0.061) to partially inhibit the effect of morphine (10 mg/kg) on prolactin secretion at a dose of 2.0 mg/kg. The decrease in plasma concentrations of TSH after morphine at a dose of 10 mg/kg (p less than 0.001) remained unaffected by any of administered doses of Tyr-MIF-1. The results suggest that Tyr-MIF-1 may affect the regulation of the secretion of some anterior pituitary hormones.
Veterans Affairs Medical Center, New Orleans, Louisiana.
Z K
ZK
Krowicki
A J
AJ
Kastin
D000595:Amino Acid Sequence; D000818:Animals; D004347:Drug Interactions; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D013006:Growth Hormone / Q000378:metabolism; D007700:Kinetics; D007986:Luteinizing Hormone / Q000378:metabolism; D009075:MSH Release-Inhibiting Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D008969:Molecular Sequence Data; D009020:Morphine / Q000494:pharmacology*; D010052:Ovariectomy; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D010908:Pituitary Hormones, Anterior / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013972:Thyrotropin / Q000378:metabolism
D010908:Pituitary Hormones, Anterior; D009020:Morphine; C036930:tyrosyl-prolyl-leucyl-glycinamide; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D013972:Thyrotropin; D013006:Growth Hormone; D009075:MSH Release-Inhibiting Hormone