ABSTRACT
Embryonic and neonatal myocytes have been shown to differ in some structural and metabolic aspects from mature myocytes. Manipulation of myocyte environment is relatively simple, for cardiac myocytes are large and sediment rapidly without centrifugation, allowing incubation medium to be sampled or changed without trauma to the cells. The significant differences between whole myocardial and myocyte content occur in the cases of adenosine deaminase, purine nucleoside Phosphorylase, and xanthine oxidase, all present in lesser amounts per gram wet weight in myocytes than in whole heart. The reduction in total adenine nucleotides parallels the number of myocytes changing from healthy rod-shaped to irreversibly hypercontracted “square” cells. The location of 5'nucleotidase has been the subject of debate, the importance of which should be seen in the context of both production of adenosine as a mediator of coronary artery dilation and platelet performance, and of depletion of myocyte purine nucleotides.
