Effects of polychlorinated biphenyl 19 (2,2 ',6-trichlorobiphenyl) on contraction, Ca2+ transient, and Ca2+ current of cardiac myocytes

Polychlorinated biphenyls (PCBs) have been known as serious environmental p ollutants, causing developmental delays, motor dysfunction, and decrease in brain dopamine level in humans and animals. We have investigated the effec ts of a PCB congener, 2,2 ' ,6-trichlorobiphenyl (PCB 19) on contractile fo rce, Ca2+ transient, and L-type Ca2+ current (I-Ca,I-L) in guinea pig ventr icular myocytes stimulated at a rate of 0.25-0.33 Hz. PCB 19 decreased cont ractile force in a concentration-dependent manner. During the negative inot ropic response, the action potential duration at 20% (APD(90)), 90% of repo larization (APD(90)), and the action potential amplitude (APA) were decreas ed concentration dependently: 30 muM PCB 19 reduced APD(20), APD(90), and A PA by 36.7 +/- 3.5%, 22.6 +/- 3.9%, and 2.4 +/- 0.6%, respectively (n = 11, p < 0.01). PCB 19 30 muM decreased the Ca2+ transient and the I-Ca,I-L by 46.8 +/- 1.8% (n = 9, p < 0.01) and 47.1 +/- 3.1% (n = 9, p < 0.01), respec tively. The results suggest that PCB 19 decreased the Ca2+ transient throug h inhibition of L-type Ca2+ channels and that the decreased Ca2+ transient consequently caused a negative inotropic effect in cardiac myocytes.