THE EFFECT OF INSULIN ON INTRACELLULAR CA LCIUM-CONCENTRATION IN ESSENTIAL-HYPERTENSION IN-VITRO

The effect of insulin on cytosolic free calcium concentration (Ca2+!i ) was investigated in lymphocytes from 23 essential hypertensive patie nts and 17 normotensive control subjects. Ca2+!i was measured using t he calcium-sensitive fluorescent dye fura-2 at 510 nm emission with ex citation wavelengths of 340 nm and 380 nm. Leakage of the dye was eval uated by quenching of extracellular fluorescence using MnCl2. After in cubation of lymphocytes with 2 U/ml insulin for 3 h the resting Ca2+! i was not significantly different compared to the control value in ess ential hypertensive patients (27.6 +/- 1.6 nM vs 27.3 +/- 2.1 nM, mean +/- SEM) and in normotensive control subjects (24.7 +/- 1.3 nM vs 23. 5 +/- 1.3 nM). Now lymphocytes were stimulated by concanavalin A. Afte r incubation of lymphocytes from essential hypertensive patients with insulin, the concanavalin A-induced Ca2+!i increase was significantly reduced compared to the control value (5.2 +/- 1.0 nM vs 7.7 +/- 1.0 nM, p < 0.02). On the other hand, the concanavalin A-induced Ca2+!i i ncrease was not significantly different in the absence or presence of insulin in lymphocytes from normotensive control subjects (7.6 +/- 0.9 nM vs 7.7 +/- 1.0 nM). It is concluded that the effects of insulin on regulation of Ca2+! i are impaired in essential hypertensive patient s.