Mechanism of action of the new cardiotonic suphan on calcium exchange in cardiomyocytes

Effects of suphan, a new cardiotonic agent containing succinyl tryptophan, on the entry of Ca²⁺ into rat cardiomyocytes, its intracellular compartmentalization, and its exit from these cells were evaluatedin vitro. It was found that the recorded sulfan-induced rise of intracellular calcium was due to Ca²⁺ entering the cell via L-type calcium channels, and that a reversible reduction of its concentration in the sarcoplasm occurred through its accumulation in the sarcoplasmic reticulum and was blocked by the specific Ca²⁺-ATPase inhibitor thapsigargin (10 μM). Suphan did not alter the activity of Na⁺/Ca²⁺ exchange in a concentration range of 5–150 μg/ml. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 122, No. 7, pp. 57–59, July, 1996