SYSTEMIC HEMODYNAMICS AND RENAL-FUNCTION DURING LONG-TERM PATHOPHYSIOLOGICAL INCREASES IN CIRCULATING ENDOTHELIN

Although recent studies have reported endogenous plasma endothelin levels to be elevated two- to fivefold in chronic pathophysiological states, whether such an increase in circulating endothelin levels alone can lead to significant long-term alterations in cardiovascular and renal function is not known. The purpose of this study was to examine the long-term systemic hemodynamic and renal effects of a pathophysiological increase in plasma endothelin concentration in chronically instrumented, conscious dogs (n = 7). Infusion of endothelin-l (2.5 ng.kg(-1).min(-1)) for 8 days increased plasma concentration of immunoreactive endothelin approximately two- to threefold from 6.7 +/- 0.4 to 16.0 +/- 2.2 pg/ml. Mean arterial pressure increased 21% from a control value of 86.7 +/- 2.1 to 105.0 +/- 2.5 mmHg during the endothelin infusion period. Cardiac output averaged 2,200 +/- 205 ml/min during control and fell by 33% on day 4 of endothelin infusion (1,484 +/- 146 ml/min) and was still 14% below control after day 8 of endothelin infusion (1,885 +/- 154 ml/min). Endothelin increased total peripheral resistance from 42.0 +/- 8.1 to 80.3 +/- 9.1 mmHg.l(-1).min. Increasing plasma endothelin two- to threefold was associated with an increase in renal vascular resistance and decreases in glomerular filtration rate and renal plasma flow. Endothelin-1 had no long-term effect on plasma renin activity or aldosterone concentration. These data indicate the importance of pathophysiological levels of endothelin in controlling renal and cardiovascular function in chronic conditions. Furthermore, the results indicate that endothelin may play a role as a mediator of chronic hypertension in pathophysiological states associated with endothelial dysfunction.