Calyculin a increases voltage-dependent inward current in, smooth muscle cells isolated from guinea pig taenia coli

Abstract

The effects of a potent phosphatase inhibitor, calyculin A (CL-A), on inward currents in guinea pig taenia coli smooth muscle cells were examined. CL-A increased the inward current, and this effect of CL-A was inhibited by a protein kinase C inhibitor, H-7, and by nifedipine. Phorbol 12,13-dibutyrate, an activator of protein kinase C, also increased the inward current and this effect was antagonized by H-7. These results suggest that in guinea pig taenia coli smooth muscle cells CL-A may facilitate the opening of the L-type Ca2+ channels through the protein kinase C-dependent phosphorylation system.

Role of L-type calcium channels and PKC in active tone development in rabbit coronary artery

“…Activation of PKC via PDBu led to a significant increase in Ca v current, which was reversed by either chelerythrine or the classical PKC inhibitor Gö-6976. This is the first time a PKC activator has been shown to directly stimulate Ca v currents in a coronary myocyte, although PKC activators have been reported to enhance Ca v currents in several other smooth muscles (6,8,57). Previous studies using PKC inhibitors also suggest that PKC can directly enhance Ca v currents in coronary artery (37,43).…”

“…Numerous studies (2,10,15,18,22,26,37,39,45,52,64) have suggested that PKC activity contributes to myogenic tone in microvessels. PKC can cause smooth muscle contraction via a number of different pathways, including 1) changes in ionic conductance that depolarize E m , leading to an increase in Ca v activity (12,19,52); 2) direct stimulation of Ca v (6,8,57); and 3) increased sensitivity of the myofilaments to Ca 2ϩ (15,18,39). In coronary artery, chelerythrine reversed active tone development and caused repolarization.…”

Activation of L-type Ca2+channels by protein kinase C is reduced in smooth muscle-specific Na+/Ca2+exchanger knockout mice

“…Three different inhibitors of PKC, BIM 1, Ro-31-8220, and PKC 19-31, all decreased LVGC activation and prevented the PDBu-induced increase in LVGC activity, indicating that PDBu enhances channel activity by activating PKC. Several previous reports have suggested that PKC activates LVGCs in SM (2,3,8,19,26). The stimulation of LVGCs by PKC is often followed by inhibition, both in cardiac and SM myocytes (16,23).…”

Inhibitory effect of muscarinic receptor activation on Ca2+ channel current in smooth muscle cells of guinea‐pig ileum.

“…Bernheim, Beech & Hille (1991) as staurosporine and H-7, had little effect on the sustained phase of 'Ca suppression. In fact, these substances slightly inhibited 'Ca, and PMA, an activator of PKC, potentiated ICa This branch of the PLC pathway would be involved in potentiation of ICa' as in other mammalian smooth muscle cells (Usuki et al 1991;Yabu et al 1992). Musearinic receptor stimulation leads to an increase in guanosine 3', 5'-cyclic monophosphate (cGMP) levels in the longitudinal muscle of guinea-pig ileum (Keith, Burkman, Sokoloski & Fertel, 1982).…”