Effects of octylguanidine on heart activity: 2. Mechanical cardiac response of guinea-pig as compared to Xenopus.

The effects of octylguanidine on the mechanical activity of Guinea-pig heart were investigated. The negative inotropic effect took place in a biphasic manner with a first fast contraction decline process followed, after a temporaneous steady state, by a second slower one, respectively associated with the membrane and the metabolic action. A comparison with the biological action in Xenopus was made: the activity is foundamentally the same, although individual differencies can be found. These can be interpreted on the bases of the ultrastructural differencies of the two tissues and of the different operative temperatures, and are consistent with the hypothesis of the formation of the octylguanidine-membrane complex.