Distribution of Cyclic‐GMP‐Dependent Protein Kinase in Various Rat Tissues and Cell Lines Determined by a Sensitive and Specific Radioimmunoassay

Abstract

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.