|Budget Amount *help
¥5,000,000 (Direct Cost: ¥5,000,000)
Fiscal Year 1988: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1987: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1986: ¥3,000,000 (Direct Cost: ¥3,000,000)
Excitability of cell membrane is determined by a relative intensity of inward and outward currents across the membrane, and in smooth muscle inward current is carried by Ca ions and outwaed current K ions. In this study, we have recorded channel current or membrane currents with so-called patch-clamp methods after isolating single cells. The most commonly odserved K-channel is activated by intracellular Ca, but calmodulin is not involved in this process. Its gating mechanism is affected by many other factors, such as membrane potential, pH, and ATP. Intracellular acidification decreases, while alkalinization increases channel activity. It was also found that this channel is involved in the inhibitory action of catecholamines,likely to be mediated by an increase in intracellular Ca concentrations. Ca-channel current was also increased by intracellular alkalinization. In the porcine coronary artery, which has predominantly L-type Ca channels,Ca-channel current was increased by activatio of -adrenergic receptors. Since forskolin, which directly activates adenylate cyclase, had the similar effect to catecholamines, it is considered that -action is mediated by intracellular cyclic AMP. It is, however, necessary to find out the physiological significance of the potentiation of Ca current by activation of -receptors, which ptoduces relaxation.