Intestinal vasoregulation in spontaneously hypertensive rats.

The intestinal vascular responses to graded reductions in arterial pressure and elevations in venous pressure were measured in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. Blood flow and capillary pressure were measured in denervated, autoperfused segments of small intestine. Blood flow, capillary pressure, and total vascular resistance were significantly higher in SHR than WKY at the resting mean arterial pressures. Decrements in arterial pressure led to significant reductions in total vascular resistance in WKY but not in SHR. There was a significant tendency for capillary pressure autoregulation in WKY but not in SHR. Increments in venous pressure did not alter vascular resistance in WKY, yet significantly increased total vascular resistance in SHR. The latter effect was due entirely to a rise in precapillary resistance and is consistent with an enhanced sensitivity of the vasculature to myogenic factors. Intestinal blood flow, measured using 15-micro microspheres, was not significantly different between WKY and SHR in innervated preparations. However, in denervated preparations intestinal blood flow was significantly higher in SHR than WKY, indicating that there is a significant neural component to the increased intestinal vascular resistance in SHR.