Cytochemical effect of a stable PGI2 analog iloprost on guinea-pig heart in calcium-free and calcium paradox conditions.

Morphological and cytochemical effects of stable prostacyclin analog, iloprost were studied on isolated and perfused guinea-pig hearts according to Langendorff in Ca-free and Ca paradox conditions. Samples from the papillary muscles and left ventricular wall-muscles were examined. For calcium cytochemistry lead acetate and potassium pyroantimonate, and for nickel cytochemistry dimethylglyoxime (DMG) techniques were used. Electron microscopic studies showed that during Ca-free perfusion (for 15 min) and the following Ca repletion (for 15 min) disruption of the sarcolemma, damages in the sarcotubular system and in the mitochondria and gradual separation of intercalated discs were observed. Treatment with iloprost (1 microM) prevented those alterations in Ca-free and Ca paradox conditions. Iloprost caused a change in the intracellular distribution of Ca2+, decreased the cytochemically-demonstrated calcium in the cytoplasma, and inhibited the formation of calcium phosphate granules in mitochondria. Iloprost did not modify the number of nickel-DMG complexes either in Ca-free or in Ca paradox conditions. This study indicates that iloprost prevents the morphological damages caused by Ca paradox. The study also suggests that iloprost has an effect on the intracellular handling of calcium.