Protection of cardiac myocytes from hypothermic injury by cardiac fibroblasts isolated from neonatal rat ventricle.

In this study, we evaluated the functional and biochemical effects of cardiac fibroblasts (CFs) on cardiac myocytes (CMs) incubated under hypothermic conditions. CMs and CFs were isolated from neonatal rat ventricles and cultures of myocytes only or myocytes in coculture with CFs were established. A CM and CF concentration of 2.5 x 10(5) cells/ml was chosen and the optimum proportion of CF was determined to be 33% (ml CM:ml CF) as follows: 6:0 (group C-a), 4:0 (group C-b), 4:2 (group M-F). On the fourth day of culture, cells were incubated at 4 degrees C for 6, 12, 18, 24, 36 and 48 hr. After each incubation, creatine phosphokinase ((PK) and lactate dehydrogenase (LDH) were measured in the medium, and then the cells were cultured for an additional 24 hr at 37 degrees C to evaluate the recovery of the CM contracting rate. In groups C-a and C-b (n = 6 each), the recovery ratio of CM contracting rate decreased at 18 hr (C-a, 59.0; C-b, 55.6% of control; i.e., contracting rate prior to hypothermic incubation), reaching null levels at 48 hr. However, group M-F (n = 6) showed a significantly increased recovery at 18 hr (95.7%, P < 0.05; at 48 hrs, 27.6%). Release of CPK and LDH in groups C-a and C-b increased gradually by 24 hr and showed a marked increase at 48 hr (C-a, 114.3 x 10(-2), 194.2 x 10(-2); C-b, 81.6 x 10(-2), 118.6 x 10(-2) IU/flask, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)