Guinea pig pulmonary mechanics: Altered sensitivity to carbachol by cadmium and/or selenium

Male Hartley guinea pigs (480-610 g) were treated intratracheally as follows: saline, cadmium (Cd, 0.3 mg), selenium (Se, 0.3 or 0.06 mg), or Se (0.06 mg) and Cd (0.3 mg) simultaneously. Selenium and Cd were administered as sodium selenite and cadmium chloride, respectively. Twenty-four h later, dynamic lung compliance (C-dyn) and pulmonary resistance (R-p) were measured before (baseline C-dyn and R-p) and after carbachol administration (0.0001, 0.001, 0.01, and 0.1 mu mol/kg, intravenously). Results indicated a significant decrease in baseline C-dyn, caused by 0.3 mg of Cd, 0.3 mg or 0.06 mg of Se, and 0.3 mg of Cd with 0.06 mg of Se (p < 0.05). A significant increase in baseline R-p due to 0.3 mg of Se was observed (p < 0.05). Carbachol decreased C-dyn significantly below baseline, evident after lower doses of carbachol, in guinea pigs pretreated with 0.3 mg of Se, whereas a significant improvement in C-dyn was seen after 0.0001 mu mol/kg carbachol in the group pretreated with Se and Cd simultaneously (p < 0.05) compared with the respective baseline values of the saline-treated group. Similarly, a significant increase in R-p was observed after carbachol in groups pretreated with 0.3 mg of Cd or Se (p < 0.05). Results also indicated a significant increase in large air-way constriction caused by Cd and/or Se (p < 0.05). A leftward shift in the carbachol dose-response curve indicated increased sensitivity to carbachol in Cd- and/or Se-pretreated guinea pigs.