Effects of chronic cadmium exposure on contractility of the rat detrusor

Abstract.

The chronic effects of Cd²⁺ on the myogenic contractions induced by acetylcholine (ACh), and the neurogenic contractions induced by electrical field stimulation (EFS) of the rat detrusor were investigated. Wistar Kyoto rats weighing 150–250 g were randomly divided into four groups each containing ten animals. Three groups received intraperitoneal Cd²⁺ (0.25, 0.5 and 1 mg/kg, respectively) dissolved in saline twice a week for 3 months. The control group received only saline (0.3 ml). At the end of 3 months, the urinary bladders were surgically removed and a strip of detrusor was prepared from each bladder. An atomic absorption device and the standard addition method were used to determine blood levels of Cd²⁺ and the Cd²⁺ levels of the remaining parts of each bladder. The responses of the detrusor strips were studied in organ chambers. The tissues were first treated with ACh and then with EFS. The responses were recorded by isotonic transducers. The tissue Cd²⁺ levels were significantly increased in the Cd²⁺ treated rats in a dose-dependent manner except in the 0.25 mg/kg Cd²⁺ treated group. ACh-induced contractions were significantly attenuated only in the 1 mg/kg Cd²⁺ treated rats. The contractions induced by EFS were significantly decreased in all of the Cd²⁺-treated groups, but there were no significant differences between the groups. This study showed that Cd²⁺ exposure for 3 months impairs neurogenic and myogenic contractile activity in the rat detrusor muscle. This action seems to be at least partly due to an inhibition of the cholinergic muscarinic system. This may have clinical implications for people who are exposed to Cd²⁺.