Effects of manganese on Q-T interval and distribution of calcium in rat heart

¹ Department of Medicine, University of Oklahoma Medical Center, and Medical and Research Services, Veterans Administration Hospital, Oklahoma City, Oklahoma

Electrocardiographic observations were correlated with the 2- and 24-hr uptake of Ca⁴⁵ by the myocardium of the normal rat and the rat injected subcutaneously with manganese chloride. The distribution of Ca⁴⁵ in the heart cell was determined by differential centrifugation and the effects of manganese noted. Normally, about 40% of the Ca⁴⁵ in the rat heart was found in the microsomal fraction, the remainder being distributed equally in the other cell fractions at 2 hr. None was found in the supernatant material after centrifuging for 17 hr. After manganese injection the total uptake of Ca⁴⁵ was doubled at 2 hr due to increases in the microsomal and 17-hr fractions. Control values were re-established by 24 hr. Electrocardiograms showed a significant prolongation of the Q-T interval at 2 and 24 hr after manganese injection. There was a significant decrease in serum calcium concentration 24 hr after the injection of manganese.

Note:
With the Technical Assistance of Eleanor C. Haygood and Robert L. Trendley

Key Words: intracellular calcium • electrocardiogram • microsomes cell fractions

Submitted on May 28, 1963