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 μmol/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 μmol/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 airway 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. Accepted for publication: 14 March 1997