Abstract
In humans,release of GH due to insulin induced hypoglycemia was noted to inhibit the basal level of the pineal hormone melatonin(MEL) (Gupta et al,1983)and viceversa(Smythe and Lazarus, 1974).In order to study the interaction between stimulated GH and and MEL in adult male rats,the following studies were carried out:1.Effect of GH stimulation with GRF(1μg/bw,iv) ,l-dopa(5μg iv) and insulin hypoglycemia(4IE iv) on circulating MEL. 2.Effect of MEL(50μg sc for 4 days) on basal GH levels and effect of GH(50μg sc for 4 days) on circulating MEL concentrations. 3.Effect of MEL(50μg sc at -60 and -30 min) on GH release due to GRF,l-dopa and insulin. A significant(p < 0.01) increment in GH level(188±7 ng/ml,x±SEM) due to GRF decreased MEL concentrations while peaking of the former was synchronized with the nadir of the latter.The other two GH stimulators,although less effective,also suppressed MEL levels significantly(p < 0.05).MEL pretreatment suppressed significantly GH levels from the control(1.7±1 vs 16.7± 8,p < 0.05).Similarly,GH treated animals showed significantly suppressed MEL levels in relation to the controls(3.1±2 vs 70.9±8 pg/ml,p < 0.001).When GRF,1-dopa or insulin was administered to stimulate GH in the MEL pretreated animals,the peak was entirely abolished.The fact that the GRF induced GH release suppressed MEL and pretreatment with MEL suppressed the GH response to GRF indicates a possible interaction at the pituitary level.
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Rager, K., Attanasio, A., Kuzmanovic, D. et al. 200 MODULATION OF BASAL AND GRF-STIMULATED GH SECRETION BY MELATONIN AND VICE VERSA IN MALE RATS. Pediatr Res 19, 636 (1985). https://doi.org/10.1203/00006450-198506000-00220
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DOI: https://doi.org/10.1203/00006450-198506000-00220