Selective activation of norepinephrine- and epinephrine-secreting chromaffin cells in rat adrenal medulla.
The differential effects of insulin-induced hypoglycemia and cold exposure on adrenal medullary epinephrine (Epi) and norepinephrine (NE) cells were investigated in male Sprague-Dawley rats. In rats fasted overnight, insulin produced a marked hypoglycemia that resulted in a 70% decrease in adrenal medullary Epi content 3 h after the insulin was administered. No change in NE content was observed. Plasma Epi concentration was increased markedly after insulin, with a smaller increment in NE. In contrast, exposure to a 4 degrees C environment selectively reduced adrenal NE content, with the effect reaching statistical significance at 18 h. Cold exposure also led to a significant rise in plasma NE but not Epi. Both insulin-induced hypoglycemia and cold exposure significantly elevated adrenal dopamine, indicating that catecholamine synthesis was stimulated. Further evidence of enhanced catecholamine formation was the observation that inhibition of synthesis with alpha-methyl-p-tyrosine (AMT) greatly augmented the ability of insulin-induced hypoglycemia to selectively reduce adrenal medullary Epi content. Similarly, in cold-exposed animals, AMT pretreatment accelerated the NE depletion so that a significant decline was observed at 3 h. These results support the conclusion that the two major populations of adrenal catecholamine-secreting cells may be preferentially stimulated by different stressors. Moreover, augmented synthetic activity functions to maintain catecholamine stores in both Epi- and NE-secreting cells.
Vollmer
R R
RR
Department of Pharmacology/Physiology, University of Pittsburgh, Pennsylvania 15261.
Baruchin
A
A
Kolibal-Pegher
S S
SS
Corey
S P
SP
Stricker
E M
EM
Kaplan
B B
BB
D000313:Adrenal Medulla / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D002838:Chromaffin System / Q000166:cytology / Q000378:metabolism*; D003080:Cold Temperature; D004837:Epinephrine / Q000378:metabolism*; D007003:Hypoglycemia / Q000097:blood / Q000139:chemically induced / Q000378:metabolism; D007444:Inulin; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D007444:Inulin; D009638:Norepinephrine; D004837:Epinephrine