AJP - Regulatory, Integrative and Comparative Physiology, Vol 243, Issue 3 289-R295, Copyright © 1982 by American Physiological Society
Fluctuations in basal levels and effects of altered nutrition on plasma somatostatin
B. C. Hansen, A. Vinik, K. L. Jen and G. P. Schielke
Rapid oscillations in basal plasma levels of insulin, C-peptide, glucagon,
and glucose in rhesus monkeys have been reported previously. We now report
large minute-to-minute fluctuations in plasma somatostatinlike
immunoreactivity (SLI) in undisturbed, chair-adapted, and chronically
cannulated male rhesus monkeys. Plasma samples were drawn from eight
monkeys at 1- to 2-min intervals for 30-40 min following an overnight fast.
Large fluctuations in SLI levels with periods of 4.4-9.4 min/cycle and
possibly secondary periods of 14-18 min/cycle with average amplitudes of
+/- 23% relative to the respective mean SLI levels were observed both
within a single experiment and across monkeys under basal conditions. No
consistent relationship was found between SLI fluctuations and that of
insulin or glucagon. When portal and central blood samples were drawn
precisely simultaneously no consistent portal-central gradient was found.
Patterns of fluctuations in central and portal SLI levels were not
correlated. Overfeeding significantly increased insulin levels but did not
alter SLI levels. After 5 days of food deprivation basal SLI levels were
unchanged. These data indicate the need to exercise care in the
interpretation of single samples in the measurement of plasma SLI levels.
Somatostatin secreted into the blood under basal, unstimulated conditions
appears to be unrelated to nutritional balance.
