AJP - Regulatory, Integrative and Comparative Physiology, Vol 261, Issue 2 403-R411, Copyright © 1991 by American Physiological Society

ARTICLES

Developmental changes in adenylyl cyclase and GTP binding proteins in brown fat

A. Chaudhry and J. G. Granneman
Laboratory of Biochemical Pharmacology, Sinai Research Institute, Detroit, Michigan 48235.

During the perinatal period, norepinephrine (NE)-stimulated adenylyl cyclase activity increased in interscapular brown adipose tissue (IBAT) membranes and then declined to adult levels by 23 days postpartum. The developmental patterns of NE- and NaF-stimulated activities were identical, indicating that the developmental increase in transmitter-stimulated activity resulted from the increased interaction of alpha-subunit of guanine nucleotide-binding stimulatory protein of adenylyl cyclase (Gs alpha) with the catalytic subunit (C). This increased Gs alpha-C interaction was the result of an increase in Gs alpha specific activity, as assessed in cyc- reconstitution assays, as well as an increased C activity, as assessed by forskolin-Mn(2+)-stimulated adenylyl cyclase activity. Although adenylyl cyclase activity increased during the perinatal period, total Gs alpha levels significantly declined because of the loss of the small-molecular-mass form of Gs alpha. Thus the ratio of large to small form of Gs alpha increased threefold and might have contributed to the perinatal increase in activity. Gi alpha-like proteins, as assessed by pertussis toxin-catalyzed [32P]ADP ribosylation, declined dramatically after birth. However, this loss of Gi alpha did not contribute to developmental changes in adenylyl cyclase activity because pertussis toxin treatment failed to alter NE-stimulated activity. In contrast to G alpha subunits, there were no changes in membrane levels of G beta subunits.

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