We studied the influence of sex on the adrenal
catecholamine response to acute
insulin-induced
hypoglycemia in Sprague-Dawley rats. Eight male and seven female adult rats were anesthetized with
pentobarbital, and a microdialysis probe was placed in the left adrenal. Dialyzed
epinephrine and
norepinephrine levels were measured by high-performance liquid chromatography during a control period and for 1 hour after
insulin administration. The
blood glucose level was measured every 15 minutes. The same protocol was applied to 23 adult females at various stages of the estrus cycle. The pattern of
blood glucose changes during
insulin-induced
hypoglycemia was similar in both sexes, but males exhibited a significantly greater increase in
epinephrine than females (261% v 52%, P = .001) in the sex-comparison experiment. A similar trend was observed for
norepinephrine (73% v 0%, P = .075). The adrenal response in females for both
catecholamines was not significantly affected by the estrus cycle phase (P = .989 for
epinephrine and P = .424 for
norepinephrine). We conclude that sex influences the magnitude of the adrenal
catecholamine counterregulatory response to
hypoglycemia. Males had a significantly greater increase in
epinephrine release than females exposed to the same pattern of
hypoglycemia. Female responses to
hypoglycemia were not influenced by estrus cyclicity.