The calcium paradox and isolated myocytes.

A brief survey is presented of methods for producing Ca-tolerant ventricular myocytes, with reference to factors which might be related to the protection of the heart from the calcium paradox. Much of the analysis is based on the assumption that maintaining extracellular calcium above a 'threshold' concentration during cell isolation is a major influence on the production of Ca-tolerant myocytes, and that a similar manoeuvre in the whole organ would prevent the paradox. It is also shown that, although single cells have yet to be shown to be a good model for the paradox, measurements already reported on enzyme release and myocyte ionic homeostasis are of relevance to both Ca-tolerance and the genesis of the paradox, and that future research on isolated cells may well clarify further mechanisms important for both of these phenomena.