8-((4-chlorophenyl)thio)cyclic-3--5--gmp and kemptide

In the present study, the inhibitory effect of the cGMP analog (Rp)-8-(para-chlorophenylthio)guanosine-3',5'-cyclic monophosphorothioate ((Rp)-8-pCPT-cGMPS) on the cGMP-dependent protein kinase-mediated protein phosphorylation in intact human platelets was investigated. In vitro phosphorylation experiments with the substrate kemptide demonstrated an inhibition of the cGMP-dependent protein kinase by (Rp)-8-pCPT-cGMPS with a Ki of 0.5 microM. In intact human platelets, (Rp)-8-pCPT-cGMPS antagonized the activation of the cGMP-dependent protein kinase by 8-pCPT-cGMP without affecting cAMP-dependent protein kinase or cGMP-regulated phosphodiesterases. The data obtained suggest that (Rp)-8-pCPT-cGMPS may be a useful tool for studying the role of cGMP in vitro and in intact cells.

Topics: Animals; Blood Platelets; Blotting, Western; Cattle; Chemical Phenomena; Chemistry, Physical; Cyclic AMP-Dependent Protein Kinases; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Enzyme Activation; Humans; In Vitro Techniques; Oligopeptides; Phosphorylation; Platelet Aggregation Inhibitors; Thionucleotides