4Intracellular Free Calcium Abnormalities in Fibroblasts From Non–Insulin-Dependent Diabetic Patients With and Without Arterial Hypertension

Abstract

Abstract As arterial hypertension is frequently associated with diabetes, it is possible that altered intracellular free calcium ([Ca 2+ ] i ) handling, as reported in non–insulin-dependent diabetic patients, is accounted for by abnormalities caused by hypertension rather than diabetes. Our aim was to investigate [Ca 2+ ] i transients triggered by two extracellular agonists, bradykinin and angiotensin II, with or without chronic insulin exposure, in cultured skin fibroblasts from 10 normotensive and 10 hypertensive non–insulin-dependent patients, matched for age, body mass index, and metabolic control, with fibroblasts from 10 healthy control subjects. Long-term cultured fibroblasts were loaded with fura 2-AM for measurement of [Ca 2+ ] i . Resting [Ca 2+ ] i levels were similar in the three groups of subjects. [Ca 2+ ] i spikes stimulated by angiotensin II (0.1 μmol/L) and bradykinin (1 μmol/L) were significantly greater in hypertensive non–insulin-dependent diabetic patients (216±43 and 374±39 nmol/L, respectively) than in normotensive patients (174±16 and 267±55 nmol/L) and control subjects (188±29 and 320±78 nmol/L). Also, ionomycin evoked a greater [Ca 2+ ] i response in hypertensive than normotensive non–insulin-dependent diabetic patients and in control subjects. Chronic insulin exposure increased by 70% to 90% the [Ca 2+ ] i response to both angiotensin II and bradykinin in control subjects and normotensive non–insulin-dependent diabetic patients but not in hypertensive patients. The presence of abnormalities in [Ca 2+ ] i transients in fibroblasts from only hypertensive non–insulin-dependent diabetic patients supports the possibility that these defects are a feature of concomitant arterial hypertension rather than of diabetes or its disturbed metabolic milieu.