[Increase in the maximum intensity of myocardial contractile function using glutamic acid]. / Povyshenie maksimal'noi intensivnosti sokratitel'noi funktsii miokarda glutaminovoi kislotoi.

In experiments on 54 isolated papillary muscles from guinea-pig hearts a rise in contraction velocity and amplitude was induced by the increment in stimulation rate. Maximal contractile indices and the rate at which they were observed were the less the greater the muscle thickness limiting oxygen supply. At any rate the relaxation velocity of thin muscles (cross sectional area 0.38 mm2) was approximately twice higher than the contraction velocity. The difference became smaller as the muscle thickness increased and completely disappeared in experiments on thick muscles (cross sectional area 1.34 mm2). Addition of glutamic acid (3.5 mM) to perfusate did not influence contraction and relaxation values at a rate of 0.5-2.0 Hz but prevented their depression at a rate of 2.5-3.5 Hz, which was typical of thick muscles. This effect seems to be related to improved energy production by myocardial cells during hypoxia or ischemia.