AJP - Endocrinology and Metabolism, Vol 252, Issue 5 E588-E594, Copyright © 1987 by American Physiological Society
Opposite regulatory effects of cAMP and cGMP on sugar uptake in rat thymocytes
J. Segal
The present study provides several lines of evidence which indicate that in
the rat thymocyte adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine
3',5-cyclic monophosphate (cGMP) induce opposing regulatory effects on
2-deoxyglucose (2-DG) uptake; cAMP is stimulatory, whereas cGMP is
inhibitory. First, the cyclic nucleotide analogues dibutyryl cAMP (dBcAMP)
and dibutyryl cGMP (dBcGMP) produced a dose-related increase and decrease
in thymocyte 2-DG uptake, respectively. Second, 3,5,3'-triiodo-L-thyronine
(T3) and epinephrine, which increased cellular cAMP concentration but had
no effect on cellular cGMP concentration, increased 2-DG uptake in the rat
thymocyte. Third, dBcGMP inhibited the stimulatory effects of dBcAMP, T3,
and epinephrine on thymocyte 2-DG uptake. Fourth, prostaglandin E1 and the
inhibitors of the cyclic nucleotide phosphodiesterases,
3-isobutyl-1-methylxanthine, theophylline, and caffeine, all increased both
cellular cAMP and cGMP concentration but had no effect on 2-DG uptake.
Insulin did not change cellular cAMP and cGMP concentration, but produced a
dose-related increase in 2-DG uptake by the rat thymocyte. From these
results I have concluded that in the rat thymocyte cAMP and cGMP produce
opposite effects on sugar uptake and that the effect of certain, but not
all, agents on thymocyte sugar uptake results from their modulation of
cellular cAMP and cGMP concentration.
