INTRACELLULAR MAGNESIUM HOMEOSTASIS IS INVOLVED IN THE FUNCTIONAL RECOVERY OF PRECONDITIONED RAT-HEART

The role of ionic derangements in preconditioned hearts (PC) was assessed by measuring pH(i), high-energy phosphates (HEP) and [Mg2+] by 31P-NMR. Control (C) Langendorff rat hearts were subjected to 30′ ischemia and 30′ reflow. PC underwent 4 x (2′ ischemia + 3′ reperfusion) before prolonged ischemia and reflow. In this model, the contractile recovery of PC hearts at the end of reflow (rate-pressure product RPP: 50 ± 12% vs. 5 ± 5% of C, p = 0.004) is not related to higher HEP or pH(i) levels than in C. [Mg2+](i) increased significantly during ischemia both in C and PC organs; upon reperfusion its level remained significantly high in C (p < 0.001), while it regained the normal values in PC hearts. This behavior might improve in turn the SR calcium handling in PC organs, eventually contributing to the contractile recovery. © 1993 Academic Press, Inc.