Preservation of metabolic reserves and function after storage of myocytes in hypothermic UW solution

Isolated rat myocytes cold stored anaerobically up to 24 h in University of Wisconsin solution lost 95% of their ATP and 100% of their glycogen. They underwent contracture when rewarmed mi a Krebg-Henseleit (KH) medium that c ontained Ca unless Ca addition was delayed. In the latter case, cell functi on, measured by stimulation-induced cell shortening, was surprisingly well retained. Aerobically stored cells were resistant to Ca on rewarming, altho ugh 96% of glycogen was still lost, along with 46% of ATP. Cells that were incubated for 48 h aerobically with the substrates glucose and pyruvate at pH 6.2 retained 77% of their ATP and 59% of their glycogen, with good cell morphology. At pH 6.2, the demand for ATP was only 55% of that at pH 7.4. H owever, after rewarming, these cells functioned no better than anaerobicall y stored cells, although their inotropic response to isoproterenol was impr oved. We conclude that 1) aerobic conditions with substrates at low pH pres erve myocyte metabolic reserves well for 48 h, partly by reducing the deman d for ATP; 2) rewarming conditions are critical for anaerobically stored ce lls with metabolic stores that are severely depleted; and 3) unloaded cell function is surprisingly insensitive to a period of severe metabolic depriv ation.