AJP - Regulatory, Integrative and Comparative Physiology, Vol 253, Issue 5 772-R778, Copyright © 1987 by American Physiological Society
Pulsatile secretion of growth hormone and insulin in relation to feeding in rats
P. Even, J. Danguir, S. Nicolaidis, C. Rougeot and F. Dray
Centre National de la Recherche Scientifique UA 637, College de France, Paris.
In unrestrained male Wistar rats chronically implanted with intracardiac
catheters, blood samples were taken every 20 min throughout the 24 h of the
diurnal cycle. Plasma concentrations of growth hormone (GH), insulin, and
glucose were measured. The pattern of food intake was continuously
monitored. The existence of 3-h pulsatile cycles of GH secretion was
confirmed. In addition, short bursts of insulin secretion were observed in
the middle of every second GH peak-to-peak interval. Food intake appeared
to be enhanced during short periods that corresponded with GH release into
the blood and was reduced during the GH peak-to-peak periods in which the
bursts of insulin secretion were observed. From these observations this
study draws a schematic relationship between the rhythmicity of the
secretion of GH and insulin and the probability of occurrence of feeding.
We speculate that the rhythmic endocrine activity may be causally related
to feeding.
