AJP - Regulatory, Integrative and Comparative Physiology, Vol 262, Issue 4 659-R665, Copyright © 1992 by American Physiological Society
Evidence against a humoral control mechanism in adrenal catecholamine secretion during insulin-induced hypoglycemia
L. Lamarche, N. Yamaguchi, F. Peronnet and F. Guitard
Faculte de Pharmacie, Universite de Montreal, Quebec, Canada.
The present study tested the hypothesis that a humoral control mechanism is
involved in the enhanced adrenal catecholamine secretion during
insulin-induced hypoglycemia. The experiments were carried out in
anesthetized dogs in which neuronal and humoral components were
simultaneously determined by measuring catecholamine output from the right
innervated and the left acutely denervated adrenal gland, respectively.
Different levels of hypoglycemia were induced by intravenous injection of
insulin with doses of 0.075 (n = 6), 0.150 (n = 6), and 0.300 IU/kg (n = 6)
in three separate groups of dogs. Catecholamine output in the right
innervated gland increased dose dependently (P less than 0.05), reaching a
maximum level 45 min after insulin administration. By contrast,
catecholamine output from the left denervated adrenal gland remained
unchanged at all doses tested. In sham-denervated animals (n = 7),
catecholamine output from the left adrenal gland increased to a magnitude
similar to that observed in the right innervated gland after insulin
administration. Plasma glucose concentration significantly decreased in a
dose-dependent manner, reaching a nadir 30 min after insulin
administration. Maximum decreases in plasma glucose concentration could be
strongly correlated with maximum increases in catecholamine output from the
right innervated adrenal gland (r = -0.66, n = 18, P = 0.011), but not with
those from the left denervated gland (r = -0.32, n = 18, P = 0.455). The
present results do not support the functional existence of a humoral
mechanism permitting the release of adrenal catecholamines during
insulin-induced hypoglycemia.
