CONGENER-SPECIFIC EFFECTS OF PCBS ON CONTRACTIONS OF PREGNANT RAT UTERI

Both increased and decreased gestation lengths have been reported foll owing exposures to polychlorinated biphenyl (PCB) mixtures and congene rs. Because oscillatory uterine contractions are essential for parturi tion, we hypothesized that the disparate findings on gestation length may be the result of distinct PCB congener-specific actions on oscilla tory uterine contractions. This study examined the acute effects of PC B congeners on isometric contractions of isolated pregnant uteri and t he structure-activity relationship for individual congeners. After cum ulative exposure to individual PCB congeners (0.5 mu M to 150 mu M), o scillatory contractions were: 1) not altered by 2,4,5,2',4',5'-hexachl orobiphenyl, 3,4,5,3',4'-pentachlorobiphenyl, or 3,4,3'4'-tetrachlorob iphenyl; 2) significantly inhibited by 4-hydroxy-2',4',6'-trichlorobip henyl; and 3) markedly increased by 2,4,6-trichlorobiphenyl and 2,4,2' ,4'-tetrachlorobiphenyl, when compared to solvent controls. The uteri were more sensitive to PCB congeners with ortho-substituted light chlo rination than those highly chlorinated, or those interacting with the Ah-receptor.