Effect of a protein present in experimental myocardial infarct on the excitability of the isolated rat uterus

Abstract

We have studied the effects of the extracts of homogenates of normal and infarcted myocardium on the contractil activity of the isolated uterus of rat, and also the modi­ fications caused by these extracts on the response of the uterus to the action of Acetyl­ choline and Oxytocin.

The extracts of homogenates of infarcted myocardium cause an irregular and not sistematic uterine contractil activity in 75 % of the experiences we have realized and increased the effects of the Acetylchroline and Oxytocin in all (100 %) of them. The gra­ de of increasing of the effects of the Acetylcholine has been of 22 ± 8.5 % and the grade of increasing of the Oxytocin was of 35.5 ± 10.2 % using always the same quan­ tities of extracts of infarcted myocardium (0.5 ml).

The extracts of homogenates of a normal zone of myocardium, did not show any effect on the uterine contrality and neither increased the effects of the agonistic agents used.

In the experiences in which the isolated uterus of rat had spontaneus contractil activity, the extracts of homogenates of infarcted myocardium determined a tatal inhi­ bition of that activity in 65 % of experiences. In the rest, the effect of the extracts was to decrease in a considerable degree the frequence and intensity of the contractions, which presented a variable an irregular ampleness or w'idth. In this group of experiences the extracts of homogenates of normal myocardium did not have any effect at all.

We think the observed effects with the extracts of homogenates of infarcted myocar­ dium are due to the presence in them of a protein with a double type of activity, first on the structure and permeability of the membrane of the muscular cell and second onthe conductivity system. The results we have obtained are compared with those we had obtained previously on batracius and mamalian hearts.