IN-VITRO EVALUATION OF PHOSPHATE, BICARBONATE, AND HEPES BUFFERED STORAGE SOLUTIONS ON HYPOTHERMIC INJURY TO IMMATURE MYOCYTES

In this study we evaluated cardiac myocyte viability and function unde r hypothermic conditions using three types of buffer solutions: phosph ate buffer solution (PBS), Krebs-Henseleit bicarbonate buffer solution (KHB), and Hepes buffered minimum salt solution (MSS). As a control, normal saline solution (NSS) was used. Cardiac myocytes were isolated from neonatal rat ventricles. Myocytes (12.5 x 10(5) myocytes/culture flask) were then incubated at 4 degrees C for 6, 12, 18, and 24 hours in various buffer solutions. After each incubation time, CPK and LDH w ere measured. The myocytes were then incubated for an additional 24 ho urs at 37 degrees C to evaluate the recovery of the myocyte beating ra te. Group MSS had a significantly better beating rate recovery than gr oup NSS (control) after 18 hours (MSS, 32.7%, NSS, 0.0% of control; i. e., beating rate prior to hypothermic incubation). In contrast, group KHB showed a significantly lower recovery ratio than group NSS at 12 h ours (41.0%, 78.8%, respectively), and the lowest recovery was observe d in group PBS beginning at 6 hours of hypothermic incubation (27.6%). Group MSS significantly suppressed the release of CPK and LDH compare d to group NSS at 24 hours (MSS, 246.7 and 440.2 mIU/flask; NSS, 369.7 and 821.3 mIU/flask, respectively). In contrast, groups PBS and KHB s howed significantly increased CPK and LDH levels compared to group NSS after 12 hours (PBS, 388.6 and 721.4 mIU/flask; KHB, 340.5 and 540.5 mIU/flask; NSS, 91.5 and 222.7 mIU/flask, respectively). In conclusion , Hepes buffer has cytoprotective characteristics that may be suitable for long-term hypothermic preservation of immature myocardium compare d to phosphate or bicarbonate buffer.