Inotropic Activity of Orthanilic and L-Cysteic Acid on Isolated Guinea-Pig Ventricular Strips
The positive inotropic effect of taurine in low calcium medium has been demonstrated extensively in guinea-pig (1,2,4,6,9), and chick heart (11). This effect of taurine is dose- and calcium-concentration dependent (2,6,8), and is not suppressed by the addition of propranolol (4,11), cimetidine or indomethacin (8). Furthermore, taurine antagonizes the negative inotropic effect of D-600 (7) in guinea-pig ventricular strips. More recently it has been demonstrated that two taurine-related compounds, orthanilic acid (2-aminobenzenesulfonic acid) and L-cysteic acid (Fig. 1), exert a positive inotropic effect on guinea-pig ventricular strips incubated in a medium containing 0.9 mM CaCl2 (4). This effect is dose-dependent and occurs over the same concentration range as the inotropic action of taurine (5–20 mM). It is also similar with respect to the time course (4). Both compounds are characterized by primary amino and sulfonic groups bound to adjacent carbons (Fig. 1). Chain length, sulfonic and primary amino groups are a structural requirement for taurine-like inotropic activity (4). The present study investigates other properties of these two compounds in guinea-pig ventricular strips.
KeywordsNegative Inotropic Effect Positive Inotropic Effect Calcium Medium Inotropic Activity CaC12 Concentration
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