Biochemical and functional correlates of an increased membrane density of caveolae in hypertrophic rat urinary bladder

Organ hypertrophy is often found to be associated with changes in the expression of caveolins and altered density of caveolae in the membrane A plethora of signalling intermediaries are associated with caveolae and loss of caveolae has profound effects on contractility of the urinary bladder We hypothesized that smooth muscle hypertrophy caused by bladder outflow obstruction (BOO) might lead to an altered caveola density with consequences for contractile regulation Rat BOO for 6 weeks caused a 2 56-fold increase in the number of smooth muscle caveolae per mu m membrane No changes in the expression of caveolin 1 or cavin-1 normalized to beta-actin were seen but membrane area per unit muscle volume dropped to 0 346 Hypertrophy was associated with altered contraction in response to carbachol The effect on contraction of cholesterol desorption which disrupts lipid rafts and caveolae was however not changed Contraction in response to bradykinin resisted m beta cd in control destrusor but was inhibited by it after 6 weeks of obstruction It is concluded that rat detrusor hypertrophy leads to an increased number of caveolae per unit membrane area This change is due to a reduction of membrane area per volume muscle and It does not play a role for cholinergic activation but promotes contraction in response to bradykinin after long-term obstruction (C) 2010 Elsevier B V All rights reserved