AJP - Endocrinology and Metabolism, Vol 257, Issue 3 E367-E373, Copyright © 1989 by American Physiological Society
Effects of naloxone on glucose homeostasis during insulin-induced hypoglycemia
J. A. Nash, P. M. Radosevich, D. B. Lacy, N. Rizk, H. Hourani, P. E. Williams and N. N. Abumrad
Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
The present study was designed to examine the role played by beta-endorphin
in the physiological response to the stress of insulin-induced
hypoglycemia. Three groups (n = 5, each) of conscious overnight-fasted
dogs, chronically fitted with catheters in the femoral artery and in the
third ventricle were used for these studies. Each experiment consisted of
an 80-min equilibration period (0-80 min), a 40-min basal period (80-120
min), and a 180-min (120-300 min) experimental period. One group received a
220-min intracerebroventricular (icv) infusion of naloxone (0.2 mg/h)
beginning at t = 80 min. The second group received a 3-h intravenous
infusion of insulin at 5.0 mU.kg-1.min-1 beginning at t = 120 min. The
third group received naloxone at t = 80 min and insulin beginning at t =
120 min, and both were continued throughout the experimental period. The
studies show that insulin-induced hypoglycemia was associated with a rise
in plasma cortisol, beta-endorphin, epinephrine, norepinephrine, and
glucagon. Pretreatment with naloxone diminished the rises in plasma
beta-endorphin, epinephrine, and norepinephrine without affecting the
responses of plasma glucagon and cortisol. Although the levels of
hypoglycemia achieved in the two groups were identical, glucose rates of
appearance into and disappearance from the plasma compartment were higher
in the group pretreated with icv naloxone (P less than 0.05).(ABSTRACT
TRUNCATED AT 250 WORDS)
