Abstract
The cAMP-dependent protein kinase inhibitor (PKI) and calcium-dependent cyclic nucleotide phosphodiesterase regulator (CDR) proteins were examined in the Sertoli cell-enriched (SCE) rat testis. PKI activity was stable at 100 C for 10 min whereas the rate of decline of CDR activity at this temperature was first order (t½ of 7 min). Greater than 90% of both activities were found in the soluble fraction of the cell with the remaining 10% in the participate fraction. PKI and CDR could be separated by DEAE-cellulose chromatography and by polyacrylamide gel electrophoresis. Gel filtration chromatography also resulted in their physical separation, CDR eluting slightly before PKI. Molecular weights estimated by gel filtration were 21,400 and 28,800 daltons for PKI and CDR, respectively. Sufficient PKI was present in the SCE testis to inactivate only 7% of the total cAMP-dependent protein kinase whereas CDR was present in vast excess over the amount required to activate maximally total calciumdependent phosphodies...
Published Version
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