Effect of mersalyl on isolated perfused guinea pig atria

¹ Department of Medicine, New York University College of Medicine; and Electrocardiographic Laboratory of the Third (N.Y.U.) Medical Division of Bellevue Hospital, New York City

The effects of mersalyl in concentrations of 0.4^–2 x 10^–4 m were studied on isolated perfused guinea pig atria. Mersalyl produced a moderate slowing of the heart rate, an enhanced repolarization of the transmembrane potential and a decrease in contractility of both right and left atrium. The atria eventually developed asystole which usually occurred earlier in the left than in the right atrium. Administration of 6.3 x 10^–4 m cysteine hydrochloride as a constant perfusion reversed the asystole. The improvement in both the electrical and mechanical activities occurred gradually. The mechanism of action of mersalyl is attributed to inhibition of certain protein sulfhydryls in the cell; the reactivation of function by cysteine is postulated to be due to the formation of mersalyl cysteinate.