Effects of diethyl-stilboestrol on contractile response and action potential of rabbit papillary muscle

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Abstract
The effects of diethyl-stilbestrol (DES) were studied on isolated papillary muscles from rabbits (37.degree. C). The preparation was paced at a frequency of 0.67 Hz and the muscle length was adjusted to 95% of the length of optimum force production. Membrane potentials and the isometric force production were recorded. DES (10 .mu.M) reduced peak isometric force by 44.5% (mean of 6 preparations), and maximum rate of force development was reduced to approximately the same degree. The time to peak force, the time from peak force to half relaxation and the action potential duration were not significantly affected by DES. The results are consistent with the idea that DES reduces the Ca influx during the cardiac action potential without significantly influencing the Ca reuptake during relaxation. The data are compared to the effects of DES on uterine and skeletal muscles, and the differences in metabolism of activator Ca in different kinds of muscles are discussed.

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