Pathophysiological significance of plasma endothelin in peripheral circulatory disturbances

Endothelin (ET) is produced in blood vessels and is a novel potent vasoconstrictor. Although the presence of immunoreactive ET in the circulating blood suggests that ET plays an important role in the regulation of systemic and/or local hemodynamics, the role of circulating ET has not been ascertained using human populations. We examined the values of the ET level and peripheral blood flow, including other biochemical and physiological factors, in 108 healthy adults who participated in annual health examinations of Japanese adults living in a rural community in 1992 and 1993. A small change in ET after the passage of one year showed good reproducibility of the value. ET was positively correlated with diastolic blood pressure (BP) and negatively with finger skin blood flow in healthy adults. Multiple regression analysis demonstreted that the positive relationship between ET and diastolic BP was independent of other health indicators. A detailed examination using optical spectroscopy for elderly institutionalized subjects without any trouble in the activity of daily living revealed a negative correlation of ET with saturated oxygen in blood, tissue hemoglobin volume and local blood flow and a positive one with the local oxygen extraction fraction. The present study indicated that increased ET in the elderly subjects was associated with hypoxia not only in the local finger skin region, but also possibly in the arterial tissue, suggesting that ET is involved in atherosclerosis. The negative correlation between ET and finger skin blood flow seen in the healthy adults may be induced by hypoxia. Although we recognized a positive correlation between ET and BP, the increase in ET seemed to be an outcome of elevation in BP rather than a cause of hypertension.