Changes of contraction rhythm during ischemia/reperfusion in cultured cardiac myocytes

We analyzed the changes in fluctuation of contraction rhythm of cultured cardiac myocytes caused by simulated ischemia/reperfusion. Under the ischemia-like condition, the contraction intervals and the fluctuation of them increased as the ischemic time increased, and then myocytes stopped contraction by 3 hrs of the ischemia in many cases. The fluctuation temporarily decreased after reoxygenation compared with that before simulated ischemia, and then returned to the pre-ischemic level. The intracellular pH ([pH]_i) of myocytes gradually decreased through the ischemic period. However, the myocytes in an aggregate exhibited synchronized contraction with each other throughout the ischemic period. These results suggested that the increase in the fluctuation of contraction intervals during simulated ischemia was not caused by the decrease in the electrical interaction among myocytes and the extent of [pH]_i decrease during ischemia was not so great that resulted in the electrical uncoupling of myocytes.