Biochemical properties of H(+)-Ca(2+)-exchanger in the myometrium mitochondria

Some biochemical properties of the H(+)-Ca(2+)-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 Ca(2+) 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(+)-Ca(2+)-exchanger the H(+)-Ca(2+)-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(+)-Ca(2+)-exchanger was suppressed by antibodies against the LETM1 protein. Calmodulin may act as a regulator of H(+)-Ca(2+)-exchanger by inhibiting it.