JBC, Vol. 250, Issue 16, 6460-6463, Aug, 1975
Inhibition of basal and hormone-stimulated adenylate cyclase in adipocyte ghosts by the prostaglandin endoperoxide prostaglandin H2
R. R. Gorman, M. Hamberg and B. Samuelsson
The prostaglandin endoperoxide PGH2 (15-hydroxy-9alpha,
11alpha-peroxidoprosta-5,13-dienoic acid), at a concentration of 2.8 x
10(-5) M inhibited basal adenylate cyclase activity 11% and
epinephrine-stimulated activity 30 to 35%. PGH2 inhibited
epinephrine-stimulated enzyme activity in the presence of 10 mM
theophylline, 2.5 mM adenosine 3':5'-monophosphate (cAMP), or in the
absence of inhibitors or substrates of the cAMP phosphodiesterase. When the
cAMP phosphodiesterase was assayed directly using 62 nM and 1.1 muM cAMP,
PGH2 did not affect the 100,000 x g particulate cAMP phosphodiesterase from
fat cells. The inhibition of adenylate cyclase by PGH2 was readily
reversible. A 6-min preincubation of ghost membranes with PGH2, followed by
washing, did not alter subsequent epinephrine-stimulated adenylate cyclase
activity. During epinephrine stimulation, the PGH2 inhibition was apparent
on initial rates of cAMP synthesis, and the addition of PGH2 to the enzyme
system at any point during an assay markedly reduced the rate of cAMP
synthesis. Between 2.8 x 10(-7) M and 2.8 x 10(-5) M, PGH2 inhibited
epinephrine-stimulated enzyme activity in a concentration-dependent manner.
The stimulation of adenylate cyclase by thyroid-stimulating hormone,
glucagon, and adrenocorticotropic hormone as well as by epinephrine was
antagonized by PGH2, suggesting that PGH2 may be an endogenous feedback
regulator of hormone-stimulated lipolysis in adipose tissue.