AJP - Endocrinology and Metabolism, Vol 248, Issue 6 712-E718, Copyright © 1985 by American Physiological Society
Developmental changes of beta-adrenergic receptor-linked adenylate cyclase of rat liver
M. S. Katz, S. R. Boland and S. J. Schmidt
beta-Adrenergic agonist-sensitive adenylate cyclase activity and binding of
the beta-adrenergic antagonist(-)-[125I]iodopindolol were studied in rat
liver during development of male Fischer 344 rats ages 6-60 days. In liver
homogenates maximum adenylate cyclase response to beta-adrenergic agonist
(10(-5) M isoproterenol or epinephrine) decreased by 73% (P less than 0.01)
between 6 and 60 days, with most of the decrease (56%; P less than 0.01)
occurring by 20 days. beta-adrenergic receptor density (Bmax) showed a
corresponding decrease of 66% (P less than 0.01) by 20 days without
subsequent change. Binding characteristics of stereospecificity,
pharmacological specificity, saturability with time, and reversibility were
unchanged with age. GTP-, fluoride-, forskolin-, and Mn2+-stimulated
adenylate cyclase activities also decreased during development, suggesting
a decrease of activity of the catalytic component and/or guanine nucleotide
regulatory component of adenylate cyclase. These results indicate that the
developmental decrease of beta-adrenergic agonist-sensitive adenylate
cyclase activity may result from decreased numbers of beta-adrenergic
receptors. Developmental alterations of nonreceptor components of the
enzyme may also contribute to changes of catecholamine-sensitive adenylate
cyclase.
