Contractile function of papillary muscles with carbonic anhydrase inhibitors.

Contractile parameters of directly stimulated rabbit papillary muscles were studied during incubation in baths containing the carbonic anhydrase inhibitors chlorzolamide (110(-3) M) or ethoxzolamide (110(-4) M). Both inhibitors caused an at least partly reversible decrease in isometric force as it has been observed in skeletal muscle, and--in contrast to the results in skeletal muscles--a decrease in time-to-peak and half-relaxation time. It is postulated that inhibition of the membrane-bound carbonic anhydrase of heart muscle might induce an intracellular acidosis and that this acidosis causes the observed effects on contractile parameters.