Attenuation of Hemoglobin-Induced Constriction in the Rabbit Basilar Artery by Protein Kinase C Inhibitor and Ca2+/Calmodulin-Dependent Protein Kinase Inhibitor

Kim, Byung Nam; Kang, Sung Don; Kim, Jong Moon

Abstract

According to the widely accepted concept that contraction of arterial smooth muscle is dependent on the Ca2+/calmodulin and protein kinase C(PKC) systems, it has been recently proposed that activation of these two systems in vascular smooth muscle cells has a bearing on the pathogenesis of cerebral vasospasm. However, most of the reported PKC inhibitors display a poor selectivity. In a rabbit "vasospasm" model, we tested the effect of a new PKC inhibitor(Bisindolylmaleimides; BIS) which has been known for a relatively high degree of selectivity, and also investigated the possible role of a inhibitor of Ca2+/calmodulin-dependent protein kinase(CAM kinase II inhibitor; KN-62). Finally, the vasodilating action of BIS was compared to KN-62. The basilar artery was visualized using transclival exposure, and its diameter monitored using videomicroscopy. Rabbit basilar artery was constricted in vivo by topical application of phorbol dibutyrate. Application of phorbol dibutyrate elicited an acute constriction, reducing arterial diameter to 46.5% of baseline diameter. Treatment with BIS (5micrometer) attenuated phorbol dibutyrate-induced vasoconstriction to 96.2% of baseline. Subsequently, application of oxyhemoglobin(oxy-Hb; 10 -4M) reduced vascular diameter to 68.5% of baseline. This vasospastic response was reversed by 91.4% or 81.3% using BIS(5micrometer) or KN-62(5micrometer), respectively. Combined applications of BIS and KN-62 to investigate the enhancing effect produced basilar arterial constriction of 94.9% of baseline. These findings demonstrate that BIS is a potent PKC inhibitor, and PKC system, rather than Ca2+/calmodulin system, appears to play a major role in the occurrence of cerebral vasospasm. Additionally, we suggest that combination of PKC with CAM kinase II inhibitor may be more useful therapeutic agents for treating cerebral vasospasm.