The effects of dietary potassium depletion on the ultrastructure of cardiac ventricular myocytes in rabbits: a morphometric study.

The ultrastructure of cardiac ventricular myocytes isolated from normal and chronically K-depleted rabbits was analysed using morphometric techniques. Myocytes from normal animals showed a quantitatively similar distribution of organelle volumes to those previously reported for isolated myocytes from rat, and for whole myocardium in a variety of species. Myocytes from animals that had been fed a K-deficient diet for 25 days had a significantly increased surface density of junctional sarcoplasmic reticulum with the T-tubules and a significant increase in the surface density of the T-system itself. There were no other differences. The increase in junctional SR and T-system may be related to the defect in cardiac contractility that has been reported for rabbit following K depletion, and may represent an adaptive mechanism acting to protect the heart against Ca overload.