Effects of neonatal administration of monosodium glutamate on plasma growth hormone (GH) response to GH-releasing factor in adult male and female rats.
Female and male rats were treated with monosodium glutamate (MSG; 4 mg/g b. wt.) as neonates and the capability of the pituitary gland to secrete growth hormone (GH) in response to an intravenous injection of human GH-releasing factor (GRF) was evaluated under pentobarbital anesthesia on 109 days of life. Immunoreactive GRF content in the pituitary stalk-median eminence tissue in MSG-treated rats was less than 20% of that of control. A significant dose-dependent plasma GH response was observed after the administration of two doses of human GRF (0.25 and 1 microgram/kg b. wt., i.v.) in both control and MSG-treated rats. The responses between MSG-treated and control rats were comparable in female rats, but they were significantly reduced in male MSG-treated rats. These results show that the pituitary's responsiveness to exogenous GRF is well preserved in MSG-treated rats despite prolonged and severe depletion of endogenous GRF and there exists a sex difference in the effect of MSG on GH secretion elicited by GRF.
D000818:Animals; D000831:Animals, Newborn; D005260:Female; D005971:Glutamates / Q000494:pharmacology*; D013006:Growth Hormone / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000032:analysis / Q000494:pharmacology*; D007031:Hypothalamus / Q000032:analysis; D007279:Injections, Subcutaneous; D008297:Male; D010903:Pituitary Gland, Anterior / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012737:Sex Factors; D012970:Sodium Glutamate / Q000494:pharmacology*
D005971:Glutamates; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D012970:Sodium Glutamate