RESUMO
PURPOSE: Calcium-activated potassium channels(KCa) may be involved in the transient outward current of the first phase of cardiac action potential. But it is still not clear whether cardiac myocytes express any Kca. We try to identify here the types of Kc, expressed in rat caridac myocytes. METHODS: We isolated total heart RNA from 50 rats(Spague-Dawley) and performed reverse transcription-polymerase chain reaction(RT-PCR) using specifically designed synthetic oligonucleotide primer sets. From the pure culture of cardiac myocyte, Kc, gene expression was detected by Southern blot analysis. RESULTS: RT-PCR revealed expressions of BKca(large-conductance Kca, rSlo) and S&,(small-conductance Kca, rSK1). We prepared cardiac myocytes pure culture(>9596 pure myocyte) using pure culture technique. RT-PCR and Southern blot analysis of rat cardiac myocyte showed only rSK1-specific band, but no rSlo-specific was detected. CONCLUSION: The expressions of more than one type of Kca are detected from rat heart. A sub-type of SKcrSK1, was expressed in cardiac myocyte, while the main subunit of BKca(rSlo) was found in cells other than myocytes, most likely in the smooth muscle of cardiac blood vessels.