Inhibitory Effect of Staurosporine on Protein Kinase C Stimulation of Airway Smooth Muscle Cells

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Abstract
Phospholipid/calcium-dependent protein kinase (protein kinase C [PKC]) is a critical system in signal transduction of many different cells including airway smooth muscle (ASM) cells. We have previously shown that after administration of different phorbol esters, specific activators of PKC, characteristic electrical and contractile changes of ASM cells can be demonstrated. Similarly, our data showed that stimulation of PKC is implicated in the process of sensitization and the specific antigen challenge response of ASM cells. In this study we examined the effect of staurosporine, a microbial alkaloid, which has been reported to be a specific inhibitor of PKC, on sensitization- and specific antigen challenge-induced electrical and contractile changes of ASM cells. The effect of staurosporine was compared with those of amiloride, furosemide, and compounds NA-0345 and H-7, both synthetic PKC inhibitors. We used ASM preparations isolated from adult male guinea pigs (Camm-Hartley strain). Changes in both membrane potential (Em), measured by a glass microelectrode technique, and isometric force, measured by copper-beryllium strain gauge, were continuously monitored. Experiments were conducted with optimal length (Lmax) of ASM preparations and at 37 degrees C. We found that the exposure of ASM preparations to staurosporine, NA-0345, H-7, amiloride, and furosemide (all in 10(-12) to 10(-4) M) had no measurable effect on the resting membrane potential or isometric force of ASM preparations. In contrast, pretreatment of ASM preparations with staurosporine, NA-0345, H-7, amiloride, or furosemide significantly attenuated (p < 0.001) phorbol myristate acetate-induced changes of ASM preparations.(ABSTRACT TRUNCATED AT 250 WORDS)