Action of E and A prostaglandins on isolated aorta of rats with spontaneous hypertension.

The action of prostaglandins of the E and A groups on isolated aortic smooth muscle strips of rats with spontaneous hypertension (Okamoto-Aoki) (SHR) was investigated in order to follow up whether, and to what extent, an alteration of vascular reactivity exists in this model of hypertension, as well as to test the effect of vasodepressor prostaglandins on vessels of spontaneously hypertensive rats. The experiments were carried out on aortic strips of 10 control normotensive rats, and of 10 SHR. The contractions of the isolated vessel strips were recorded by means of an induction coil displacement transducer on an ink-writing electron compensated registration device. The results of the study indicate that the isolated aortic strips of normotensive rats and of SHR respond by contraction to the action of vasodepressor prostaglandins, i.e. paradoxically. It was also established that the reactivity of the isolated aortic strip of SHR to vasodepressor prostaglandins is smaller in comparison to the reactivity of the aorta of control normotensive rats. An attempt is made to explain the paradoxical response of isolated aortic strips of normotensive rats, and of SHR. It is pointed out that contrary to studies on the action of angiotensin, in studies on the vasodepressor action of prostaglandins isolated aortic smooth muscle strips cannot be used as an indicator of vascular reactivity, and especially of resistance vessels reactivity, since their response to hypotensive prostaglandins is paradoxical in both normotensive and spontaneously hypertensive rats.