Abstract
We previously reported that the beating rate of single myocardial cells cultured in a conditioned medium (CM) was higher than that of cells cultured in a fresh medium. We have characterized and partially purified the beating-stimulating factor(s) of cultured myocardial cells from a conditioned medium of mouse embryonic cells.
The beating-stimulating factor(s) had stable activity for more than one month when it was freeze-dried in 0.1 M sucrose and stored at -20°C. The factor(s) was non-dialyzable and was heat-labile. It was inactivated by treatment with trypsin, pronase or hyaluronidase, but not with neuraminidase. These results strongly suggest that the beating-stimulating factor(s) is a glycoprotein(s). When concentrated CM was filtered on Sephadex G-200, the main peak of activity appeared in almost the same fractions as in those for that of hemoglobin. The SDS-polyacrylamide gel electrophoretogram of crude CM showed more than 20 protein bands and about 10 bands stainable by periodic acidSchiff (PAS). In contrast, the electrophoretogram of the active peak on Sephadex G-200 showed about 10 protein bands and one PAS-stainable band.
