title: Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on guinea pig heart muscle.
abstract: Cardiac effects of TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) were examined using atrial muscle isolated from young or mature guinea pigs fed ad libitum, from young animals 10 or 20 days after a single ip injection of 1 microgram TCDD/kg body wt, and from control guinea pigs pair-fed to the TCDD-treated animals. Basal contraction force of left atrial muscle obtained from TCDD-treated and pair-fed control guinea pigs 10 days after treatment was significantly increased compared to atrial muscle obtained from ad libitum control animals. Atrial muscle from TCDD-treated animals 20 days after treatment had a significantly lower basal force of contraction while that from pair-fed animals was significantly higher relative to atrial muscle from ad libitum control animals. These results suggest that the TCDD-induced change in basal atrial contraction force is in part due to undernutrition and that prolonged exposure to TCDD inhibits this response observed in pair-fed animals. Furthermore, prolonged TCDD treatment shifted the dose-response curve for the positive inotropic effect of isoproterenol to the right with no statistically significant change in the maximal inotropic effect obtained with high concentrations of isoproterenol. The TCDD-induced changes in force of contraction and the dose-response curve for the positive inotropic effect of isoproterenol were similar in young TCDD-treated and mature control guinea pigs. TCDD did not alter the basal contraction frequency or the dose-response curve for the positive chronotropic effect of isoproterenol. There was no effect on cardiac lipoprotein lipase activity at 1 microgram/kg, but in animals administered 4 micrograms TCDD/kg activity was reduced. It was concluded that TCDD adversely affects atrial muscle of guinea pig heart.
mesh_terms: D000818:Animals; D001835:Body Weight / Q000187:drug effects; D004147:Dioxins / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D007545:Isoproterenol / Q000494:pharmacology; D008071:Lipoprotein Lipase / Q000378:metabolism; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009929:Organ Size / Q000187:drug effects; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology*; D051381:Rats
chemical_list: D004147:Dioxins; D000072317:Polychlorinated Dibenzodioxins; D008071:Lipoprotein Lipase; D007545:Isoproterenol