Cadmium accumulation augments contraction and phosphoinositide hydrolysis of vascular smooth muscles

Effects of cadmium accumulation in blood vessels on vasoconstriction and hydrolysis of phosphoinositides were investigated using aortas isolated from rats. The aortic strips were incubated with cadmium chloride (10 microM) for 24 hr and then washed out (cadmium accumulation). In the cadmium-accumulated aortas, contractile responses to KCl and 5-hydroxytryptamine were augmented compared to the control incubated with a vehicle. The degree of the augmentation by cadmium was higher in 5-hydroxytryptamine contraction than in KCl contraction. The level of 5-hydroxytryptamine-induced contraction relative to KCl-induced contraction (expressed as percent of maximum KCl contraction in each strip) was also significantly increased in the cadmium-accumulated aortas as compared to the control. Cadmium pretreatment augmented 5-hydroxytryptamine-stimulated inositol monophosphate accumulation, while there was no difference in the basal level of inositol monophosphate between the cadmium-accumulated aortas and the control. These results suggest that cadmium accumulation increases vasocontractility, in part because of the facilitation of phosphoinositide hydrolysis.