Biochemical properties of H+-Ca2+-exchanger in the myometrium mitochondria

Abstract

Some biochemical properties of the H⁺-Ca²⁺-exchanger in uterine smooth muscle mitochondria have been described. The experiments were performed on a suspension of isolated mitochondria from the myometrium of rats. Methods of confocal microscopy, spectrofluorimetry and photon correlation spectroscopy were used. Fluo-4 probe was used to record changes in ionized Ca²⁺ in the matrix and cytosol; pH changes in the matrix were evaluated with BCECF. It was experimentally proved that in the myometrium instead of Na⁺-Ca²⁺-exchanger the H⁺-Ca²⁺-exchanger functions. It was activated at a physiological pH value, was carried out in stoichiometry 1: 1 and was electrogenic. The transport system was modulated by magnesium ions and the diuretic amiloride, but was not sensitive to changes in the concentration of extra-mitochondrial potassium ions. H⁺-Ca²⁺-exchanger was suppressed by antibodies against the LETM1 protein. Calmodulin may act as a regulator of H⁺-Ca²⁺-exchanger by inhibiting it.