Kinetic analysis of smooth muscle relaxation.

A method has been proposed for the kinetic analysis of the relaxation phase of mechanical response of smooth muscle. The method implies linearization of the entire mechano-kinetic relaxation curve using the coordinates ln[(fm-f)/f]; ln t (where fm and f are the maximal and the actual values of force within the relaxation phase respectively) with subsequent calculation of the maximal amplitude--normalized relaxation rate, Vn. The use of the method is illustrated on ureter, protal vein, vas deferens, myometrium of rat and guinea-pig ureter smooth muscles in a variety of experimental conditions. This method can be applied for the description of the calcium transient decay in the myoplasm measured with Ca-sensitive fluorescent dyes. The method might be useful for identification of the contribution of different energy-dependent Ca-transporting systems involved in the control of relaxation, as well as for screening of the mechanisms of action of different factors which modulate the contraction-relaxation cycle.