The late effect of 7-oxo prostacyclin protects the rat heart against calcium paradox.

Protective effect of a stable derivative of prostacyclin (7-oxo PGI2) was studied on the model of calcium overload (Ca paradox) 48 h after i.m. administration of the drug in a dosage of 50 micrograms/kg. In isolated rat heart perfused at 37 degrees C and a constant perfusion pressure of 65 mm Hg (Langendorff preparation) Ca paradox was induced by a 3 min perfusion with a calcium-free Krebs-Henseleit (KH) solution and followed by a 10 min perfusion with KH containing normal concentration of calcium. Late protective effect of 7-oxo PGI2 was manifested by: i. improved recovery of heart function (developed pressure and coronary flow) after Ca paradox, ii. better preservation of macroergic phosphates content, iii. better preserved cardiac ultrastructure (sarcolemma) already during Ca depletion phase. One of the proposed mechanisms of the protection afforded by the pretreatment with 7-oxo PGI2 may be that the cell membrane and possibly the intercalated discs become less affected by calcium depletion, resulting in less contracture-mediated membrane damage upon calcium repletion.