Ca2+ release in permeabilized human neutrophils induced by ciclosporin

In suspensions of permeabilized human neutrophils, the free Ca2+ concentration was measured to test the effects of ciclosporin. Free Ca2+ concentration was measured with a Ca2(+)-selective electrode. Ciclosporin (500 ng/ml) induced a transient increase in free Ca2+ concentration (maximum delta pCa, 0.41 +/- 0.17). Thereafter, the free Ca2+ concentration decreased again, but did not reach the baseline level in most experiments. Ruthenium red, but not orthovanadate, abolished the slow decline of free Ca2+ concentration after the initial increase. The experiments suggest that ciclosporin may induce a release of Ca2+ from cellular organelles, e.g. the endoplasmic reticulum, and a partial reuptake in mitochondria. A release of cellular Ca2+ may play a role in ciclosporin-induced hypertension.