Abstract
Objective: To determine whether the cutaneous microvasculature of the spontaneously hypertensive rat (SHR) is affected by chronic hypertension. Design: We used laser Doppler techniques to measure skin blood flow in 22 SHR and in 22 non-hypertensive Wistar-Kyoto (WKY) rats over a 1-year time span, beginning at age 3 months. Sites of measurement included the back, leg, and root of the tail, areas with a predominantly nutritive perfusion, and the plantar surface of the paw, which has a large contribution from large arterioles and venules. Flow was measured at basal skin temperature and at the maximally heat-stimulated condition of 44°C. Systolic tail arterial blood pressures were measured concurrently. Results: At baseline, systolic blood pressures were considerably higher in the SHR (190 ± 4 mmHg) than they were in the WKY rats (138 ± 2 mmHg). Skin blood flow values at the three nutritive sites were similar in the two species. However, at 44°C, flow was significantly higher at the paw in the SHR (46.8 ± 3.5 versus 34.3 ± 2.2 ml/min per 100 g). We attribute this difference to the effect of high perfusion pressure on large arterioles. During the 1-year measurement period, there was no appreciable change in blood flow in the WKY rats. In contrast, the SHR showed a steady progressive decline in skin blood flow at all sites. The largest decline was at the paw with a rate of fall of about 2.4%/month. After 1 year, there was no difference between paw blood flow in the SHR (27.5 ± 1.8 ml/min per 100 g) and in the WKY rats (27.6 ± 1.9 ml/min per 100 g). Conclusions: Skin blood flow reserve falls in response to chronic hypertension. The rate of fall is greater at sites with significant arteriovenous perfusion than at nutritive sites.