1030-15 Endothelin-1 Modulates Conduit Vessel Compliance as Well as Peripheral Vascular Tone: Implications for Endothelin Mediated Regulation of Blood Pressure

Abstract

Although the endothelins have well recognized effects on peripheral vascular resistance, their capacity to modulate conduit vessel tone in vivo remains incompletely defined. Therefore, characteristic impedance of the aorta was derived from measurement of central aortic pressure and flow in 6 normotensive rats at baseline and following bolus infusion of endothelin-l, the most potent peripheral vasoconstrictor of the endothelin peptides. Endothelin-l produced a typical biphasic peripheral vascular response with an initial decrease in systemic vascular resistance (svr) (dynes-sec/cm 5 ) from 2.1 × 10 5 ± 0.5 × 10 5 to 0.5 × 10 5 ± 1. × 10 5 followed by a significant (p = 0.05) increase over baseline to 2.6 × 10 5 ± 0.8 × 10 5 . A significant (p = 0.02) change in characteristic impedance of the aorta (dynes-sec/cm 5 ) was observed with an increase over the baseline value of 6.6 × 10 3 ± 2.2 × 10 3 to 8.1 × 10 3 ± 2.9 × 10 3 : which occurred immediately following bolus infusion and during the nadir, n svr, followed by a return towards the baseline value (6.6 × 10 3 ± 2.1 × 10 3 during the peak increase in svr). These in vivo data indicate that significant changes in conduit vessel tone, in addition to peripheral vascular resistance, accompany administration of endothelin-l with a significant decrease in conduit vessel compliance, reflected by increased characteristic impedance, which precedes an increase in svr. Therefore, endothelin-l modulation of systemic blood pressure may be mediated by regulation of conduit vessel compliance as well as peripheral vascular tone.