An improved method for isolating Ca2+-resistant myocytes from the adult rat heart.

Maintaining viability in cardiac myocytes isolated from adult rats using collagenase is difficult in Ca-containing media due to cell damage that occurs on reintroduction of Ca after perfusing the heart with the Ca-free medium needed to isolate myocytes with collagenase. Recently it has been proposed that Ca-free perfusion of isolated rabbit interventricular septa leads to cellular Na overload which, on reintroducing Ca, produces influx of toxic concentrations of Ca due to the Na/Ca exchange mechanism in the sarcolemma. We have found that replacing a portion of the 118 mM NaCl in the Ca-free perfusion medium with 69 mM LiCl dramatically increased the proportion of Ca-tolerant cardiac myocytes isolated from adult male rats with collagenase. Myocyte viability was maintained over a four hour period of incubation at 37 degrees C in 1 mM Ca.