Comparison of the serum insulin and endothelin level in patients with essential and renovascular hypertension.

To evaluate whether a relationship exists between insulinaemia (increased in essential hypertension) and endothelin level, we determined insulin and endothelin-1-like (ET-1-Li) immunoreactivity in blood serum by radioimmunoassay (RIA) in essential (EH, n = 64) and renovascular (RVH, n = 36) patients with hypertension and in healthy subjects (controls, n = 44). The trials were carried out in fasting patients and after an oral glucose tolerance test (OGTT, 75 g). Each group of subjects had similar body mass index (BMI) values. The mean values of insulin level were significantly (P < 0.0001 in every case) elevated in patients with essential hypertension compared with renovascular and control subjects during the whole OGTT. There was no significant difference in insulin level between subjects with renovascular hypertension and controls. ET-1-Li immunoreactivity levels were significantly increased (P < 0.005 fasting; P < 0.01 after 1 and 2 h) throughout the whole test in the essential hypertensive group compared with controls; in renovascular hypertensive patients 2 h after glucose administration the analogous difference was not statistically significant (P < 0.05 fasting; P < 0.01 after 1 h). In all the investigated groups the mean value of ET-1-Li immunoreactivity increased and decreased in parallel to the changes in insulin concentration during the OGTT. The ET-1-Li level was positively correlated with insulin concentration with a statistical significance for patients with essential hypertension 1 h after load (r = 0.6578, P < 0.05). The border of the significance level correlation was obtained in essential hypertensive patients 2 h after load (r = 0.5227, P = 0.06) and in controls 1 h after glucose administration (r = 0.5465, P = 0.054). Our results indicate a mutual connection between insulinaemia and an endothelin set; their relevance for the pathogenesis of hypertension requires further research.