Different sensitivities of Ca^2^+, calmodulin-dependent cyclic nucleotide phosphodiesterases from rabbit aorta and brain to dihydropyridine calcium channel blockers - Matsushima, S.; Tanaka, T.; Saitoh, M.; Watanabe, M.; Hidaka, H. (Elsevier)
The concentrations of the dihydropyridines, CD-349, nicardipine, and nimodipine, producing 50% inhibition of Ca^2^+, calmodulin (CaM)-dependent cyclic nucleotide phosphodiesterase (CaPDE) from rabbit aorta in the absence of Ca^2^+-CaM complex were approximately 7 to 13-fold higher than these of aorta CaPDE in the presence of Ca^2^+-CaM complex and of the trypsin treated enzyme form. On the other hand, these dihydropyridine derivatives inhibited CaPDE from rabbit brain at much the same IC"5"0 values seen in the absence and presence of the Ca^2^+-CaM complex and the trypsin-treated enzyme. Kinetic analysis revealed that these dihydropyridines inhibited the activities of CaPDEs from both the aorta and brain, competitively with cyclic GMP as substrate, and the Ki valued of CD-349 for CaPDE from aorta or brain in the absence or presence of Ca^2^+-CaM complex and trypsin-treated enzyme were 9.6, 0.75, 0.75 or 0.69, 0.70, 0.66 μM, respectively. These results suggest that CaPDE from the rabbit aorta differs from this enzyme in the brain, with regard to the relationship between the dihydropyrine binding sites on CaPDE molecules and the domains regulated by the Ca^2^+-CaM complex or limited proteolysis.
http://dx.doi.org/10.1016/S0006-291X(87)80297-8
Keywords: W; V; U