Fig. 3. ß-galactosidase activity in primary ventricular myocyte cultures. (A) The ratio of ß-galactosidase activity in left over right cultures is approximately 1 for different Mlc3f constructs and RSV-lacZ reporter genes after transfection into either rat (black circles) or nontransgenic mouse (open circles) primary ventricular free-wall cultures. (B) Decreasing the amount of Mlc3f-nlacZ-2 reporter gene does not change the ratio of ß-galactosidase activity in left or right nontransgenic cultures after transient transfection. (C) ß-galactosidase activity in transgenic cultures is cell autonomous. Co-culture with increasing amounts of rat cardiomyocytes from the opposite ventricle does not change the number of ß-galactosidase-positive cells in either left or right ventricular cultures. The average number of ß-galactosidase-positive nuclei over five fields plus s.e.m. is shown for each co-culture.