Mean circulatory pressure and vascular compliances in the spontaneously hypertensive rat

Publisher Website
Google Scholar
Abstract
Mean circulatory filling pressure (MCFP), blood volume (BV) and whole body venous capacity were measured in conscious, 20 wk old spontaneously hypertensive rats (SHR) and their Wistar-Kyoto controls (WKY). Blood volumes were similar in SHR and WKY, averaging 49.3 .+-. 2.8 (SD) and 51.0 .+-. 3.3 ml/kg, respectively. MCFP in the SHR was significantly elevated, averaging 9.1 .+-. 0.9 mm Hg compared to 7.7 .+-. 1.1 mm Hg in the WKY (P < 0.005). To evaluate venous compliance and unstressed volume in these animals, rapid blood volume changes were used to construct MCFP-BV curves. Curves for SHR and WKY were nearly parallel over the MCFP range 4-12 mm Hg, implying no difference in venous compliance: SHR compliance averaged 2.91 .+-. 0.72 ml .cntdot. kg-1 .cntdot. mmHg-1; WKY compliance was 31.3 .+-. 0.45 ml .cntdot. kg-1 .cntdot. mmHg-1. The SHR curve was shifted substantially toward the MCFP axis, suggesting a decrease in unstressed volume in the SHR. Linear extrapolation of MCFP-BV curves to MCFP = 0 yielded unstressed volumes averaging 22.5 .+-. 5.7 and 27.4 .+-. 5.7 ml/kg in the SHR and WKY, respectively (0.05 < P < 0.10). Systemic arterial compliances at low arterial pressures were also measured in phentobarbital-anesthetized rats. SHR arterial compliance was significantly below WKY compliance: 0.0274 vs. 0.0412 ml .cntdot. kg-1 .cntdot. mmHg-1, respectively (P < 0.005). The MCFP and BV data show increased venoconstriction in the SHR, producing an elevated MCFP despite their normal absolute BV. This condition may be important in the maintenance, and perhaps initiation, of the hypertensive state.

This publication has 10 references indexed in Scilit: