INSULIN STIMULATES HORMONE-SENSITIVE CYCLIC GMP-INHIBITED CYCLIC-NUCLEOTIDE PHOSPHODIESTERASE IN RAT BROWN ADIPOSE-CELLS

The presence and regulation of a hormone-sensitive cyclic GMP-inhibite d cyclic nucleotide phosphodiesterase (cGI PDE) in rat brown adipose c ells was investigated, cDNA clones for two cGI PDE isoforms, cGIP1 and cGIP2, have been isolated, Using a rat cGIP1 (RcGIP1) cDNA probe, RcG IP1 mRNA (similar to 5,3 kb) was detected in Northern blots of both br own and white adipose RNA, cGI PDE was detected in both microsomal and plasma membrane fractions of brown and white adipose cells by Western blotting using anti-RcGIP1 peptide antibody, When cells were incubate d with insulin before membrane preparation, cGI PDE activity in the mi crosomal fraction was increased by 2- to 2.5-fold within 10 min, Isopr oterenol also stimulated the activity of cGI PDE in the microsomal fra ction by 1,5-fold, In cells incubated with both insulin and isoprotere nol, microsomal cGI PDE activity,vas similar to that in microsomal fra ctions isolated from cells incubated with insulin alone. These results suggest that the hormonal regulation of cGI PDE, presumably a cGIP1 i soform, in rat brown adipose cells is similar to that in white adipose cells.