Proteinous amino acids in muscle cytosol of rats' heart, after their treatment with propranolol, pentylenetetrazol or reserpine.

Tissue levels of nineteen amino acids and total free amino acids, were assayed by gas-liquid chromatography in cytosols of rat atrial and ventricular muscle cardiomyocytes. The tissues were assayed after the rats had been administered IP with the three cardioactive drugs, exerting a significant effect on their heart action: propranolol, pentylenetetrazol and reserpine. It was demonstrated that while in the atrial and ventricular cardiac muscle cytosols of control rats, arginine, glutamine and cysteine were detected in high levels (35.1% and 17.6%; 14.8% and 51.6%; 9.9% and 0.25% of the total free amino acids, respectively), all three drugs significantly reduced the total amounts of cytosolic free amino acids in both atrial and ventricular heart muscles. All three drugs (with reserpine in particular) modified the levels of arginine, cysteine, phenylalanine, tryptophan, isoleucine and tyrosine. The role of these amino acids in the heart muscle cytosol, and their involvement in the mechanism of action of these three cardioactive drugs, is discussed.