[Effects of pH on vascular smooth muscle contraction]

Effects of pH on vascular smooth muscle contractility were reviewed. Basic effect of acidosis seems to be the inhibition of K channels and L-type Ca channels. Inhibition of K channels results in a membrane depolarization, opening of L-type Ca channels, increase in Ca influx and muscle contraction. Inhibition of Ca channels results in an opposit effect. Thus, the effect of acidosis is determined by the relative potency of these two contradictory effects. This may be the reason why acidosis induces contraction in polarized muscle whereas it slightly inhibits contraction in depolarized muscle. In addition, measurements of cytosolic Ca level simultaneously with muscle tension suggest that acidosis increases Ca sensitivity of contractile elements, and this effect also helps acidosis to induce contraction in vascular smooth muscle.