Distribution of cyclic-GMP-[guanosin monophosphate]-dependent protein kinase in various rat tissues and cell lines determined by a sensitive and specific radioimmunoassay

Cyclic‐GMP‐dependent protein kinase purified from bovine lung was radioiodinated by the Bolton‐Hunter procedure yielding a specific radioactivity of 2200 Ci/mmol of enzyme. Using a specific precipitating rabbit antiserum to the cyclic‐GMP‐dependent protein kinase, a sensitive radioimmunoassay was developed which can detect 200 pg (1.33 fmol) of cyclic‐GMP‐dependent protein kinase. Immunoreactivity like that of cyclic‐GMP‐dependent protein kinase was detectable in extracts of all rat tissues tested, in extracts of cultured rat brain and heart cells, and in extracts of rat glioma (C6) and neuroblastoma × glioma hybrid cells. In extracts of several tissues and cell lines the presence of cyclic‐GMP‐dependent protein kinase was also demonstrated by a photoaffinity‐labeling procedure using 8‐azidoinosine 3′, 5′‐[32P]monophosphate. The results suggest that cyclic‐GMP‐dependent protein kinase is ubiquitously distributed although its level varies significantly from tissue to tissue and cell type to cell type. The results also support the hypothesis that cyclic‐GMP‐dependent protein kinase is involved in mediating some of the intracellular effects of those hormones, neurotransmitters and drugs which regulate the intracellular level of cyclic GMP.