AJP - Regulatory, Integrative and Comparative Physiology, Vol 242, Issue 3 255-R260, Copyright © 1982 by American Physiological Society
Influence of nutritional state on periodicity in plasma insulin levels in monkeys
B. C. Hansen, K. L. Jen, D. J. Koerker, C. J. Goodner and R. A. Wolfe
Rapid sustained oscillations in basal plasma levels of insulin, glucose,
and glucagon (9-12 min/cycle) have been identified in rhesus monkeys and in
humans. To assess the possible regulatory role of nutritional state in the
control of these plasma fluctuations, 12 chronically cannulated conscious
rhesus monkeys were studied at varying intervals following ingestion of a
mixed meal. Blood samples were withdrawn at 2-min intervals for periods of
10-30 min. In the postprandial period both absolute and relative amplitudes
(half amplitude percent) of oscillations increased up to 16 h postfeeding
to maximal amplitudes of +/- 32% for insulin, +/- 4% for glucose, and +/-
22% for glucagon. Periods were consistently in the 9- to 12-min range for
insulin and glucose. Progressive deprivation to 88 h produced decreases in
amplitudes and more irregularity in fluctuations but did not affect the
underlying periodicity of these oscillations in plasma levels of insulin,
glucose, and glucagon. Results are consistent with the existence of one or
more inherent oscillators in the pancreas that act to synchronize the
release of hormones from particular types of islet cells. The amplitude of
these oscillations but not the frequencies is associated with changes in
liver metabolism and nutritional state.
