Possible Role of Vascular Oscillatory Activity in the Development of High Blood Pressure in Spontaneously Hypertensive Rats

Abstract

Many investigators have shown that vascular smooth muscle from hypertensive individuals shows oscillatory activity, i.e., spontaneous or rhythmic contractions. This paper reviews work performed in the author's laboratory designed to determine if the oscillatory activity of mesenteric resistance vessels taken from spontaneously hypertensive rats (SHR) is associated with the cause of the high blood pressure in these animals, as well as to determine the mechanism producing the oscillatory activity. Cross-breeding of SHR and normotensive control Wistar-Kyoto rats (WKY) was used to produce F2-SHR/WKY rats. In the F2-SHR/WKY rats, there was a correlation between systolic blood pressure and mesenteric resistance vessel oscillatory activity, but no correlation between systolic blood pressure and mesenteric resistance vessel calcium sensitivity. The oscillatory activity appeared to be associated with changes in membrane potential and is inhibited by inhibitors of potential-dependent calcium channels. This is consistent with reports from other laboratories that the oscillatory activity could be associated with an interaction between potential-dependent calcium channels and calcium-dependent potassium channels. The results suggest that the increased oscillatory activity of the mesenteric resistance vessels of the SHR is associated with a cause of high blood pressure in these animals and may be due to an abnormal activity of the calcium-dependent potassium channels.