AJP - Regulatory, Integrative and Comparative Physiology, Vol 263, Issue 4 857-R862, Copyright © 1992 by American Physiological Society
Control of adipose tissue lipolysis in ectotherm vertebrates
R. H. Migliorini, J. S. Lima-Verde, C. R. Machado, G. M. Cardona, M. A. Garofalo and I. C. Kettelhut
Department of Biochemistry, School of Medicine, University of Sao Paulo, Brazil.
Lipolytic activity of fish (Hoplias malabaricus), toad (Bufo paracnemis),
and snake (Philodryas patagoniensis) adipose tissue was investigated in
vivo and in vitro. Catecholamines or glucagon did not affect the release of
free fatty acids (FFA) by incubated fish and toad adipose tissue.
Catecholamines also failed to activate snake adipose tissue lipolysis,
which even decreased in the presence of epinephrine. However, glucagon
stimulated both the lipolytic activity of reptilian tissue in vitro and the
mobilization of FFA to plasma when administered to snakes in vivo. The
release of FFA from incubated fish, amphibian, and reptilian adipose tissue
increased markedly in the presence of cAMP or xanthine derivatives,
inhibitors of phosphodiesterase. Forskolin or fluoride, activators of
specific components of the adenylate cyclase system, strongly stimulated
toad adipose tissue lipolysis. The data suggest that adipocyte
triacylglycerol lipase of ectotherm vertebrates is activated by a
cAMP-mediated phosphorylation and that the organization of the
membrane-bound adenylate cyclase system is similar to that of mammals.
