AJP - Endocrinology and Metabolism, Vol 247, Issue 1 29-E34, Copyright © 1984 by American Physiological Society
Effects of surgical stress and insulin on cardiovascular function and norepinephrine kinetics
N. J. Christensen, J. Hilsted, L. Hegedus and S. Madsbad
In resting supine subjects the whole-body clearance of norepinephrine (NE)
based on arterial and venous sampling averaged 1.4 and 2.5 liters/min,
respectively (P less than 0.02). The difference in clearance values was due
to a peripheral uptake of NE averaging 45%. The calculation of plasma NE
clearance based on venous sampling results in values that are too high. The
plasma appearance rate of NE increased considerably after surgery, whereas
the arterial blood pressure remained unchanged. This suggests that the
sensitivity to NE is reduced postsurgery. Insulin has certain acute effects
on cardiovascular function and plasma NE kinetics that are unrelated to the
counterregulatory response to decrements in plasma glucose concentration.
Insulin may both induce antagonism to the action of NE and increase the
release of NE from sympathetic nerves. Intravenous insulin decreases the
plasma volume and increases the hematocrit by an adrenergic mechanism.
Plasma NE increases in normal subjects after an oral glucose load. This
response may be of importance because in sympathectomized patients both
oral glucose and insulin administration decreases the arterial blood
pressure. During an oral glucose load insulin-dependent diabetics show
abnormalities in the regulation of cardiovascular function and sympathetic
nervous activity that may be related to the lack of rise in endogenous
insulin in these patients. These results suggest that insulin may be of
importance for the normal function of the cardiovascular system.
