LONG-TERM HYPOTHERMIC PRESERVATION OF CARDIAC MYOCYTES ISOLATED FROM THE NEONATAL RAT VENTRICLE - A COMPARISON OF VARIOUS CRYSTALLOID SOLUTIONS

In this study, the functional and biochemical effects of crystalloid s olutions on immature cardiac myocytes incubated under hypothermic cond itions were evaluated. Cardiac myocytes were isolated from neonatal ra t ventricles and cultured for 4 days, following which 12.5 X 10(5) myo cytes per flask were incubated at 4 degrees C for 3, 6, 12; and 18 h i n five types of crystalloid solutions: lactated Ringer's (LR), St. Tho mas' Hospital (ST), University of Wisconsin (UW), 5% glucose-based pot assium (GK), and normal saline (NS). The levels of creatine phosphokin ase (CPK) and lactate dehydrogenase (LDH) in the solutions were measur ed after each hypothermic incubation, following which the myocytes wer e cultured for an additional 24 h at 37 degrees C to evaluate the reco very of the myocyte beating rate. In the LR, UW, and NS groups, the re covery ratios of the myocyte beating rate were over 95% of the control (the beating rate prior to hypothermic incubation) at 3 h, but decrea sed to 20.3, 15.1, and 0%, respectively, at 18 h. The ST and GK groups had significantly lower recovery ratios than the other three groups ( 72.9% and 63.4%, respectively) at 3 h. The release of CPK and LDH in t he LR, UW, and NS groups was significantly suppressed compared to the ST and GK groups, with the greatest suppression observed in the LR gro up. Moreover, the ST and GK groups had the highest CPK and LDH levels, respectively. Thus, LR solution had the least cytotoxic effects, indi cating that it could be the most suitable basic solution of the variou s cardioplegic or preservation solutions during the neonatal period.