The effect of pregnancy and delivery on the function and ultrastructure of the rat bladder and urethra

Objective To examine the effect of pregnancy and delivery on the function and ultrastructure of the bladder and urethra in rats. Material and methods The study comprised six virgin and 18 pregnant rats; both groups underwent cystometry (at the 19th day of gestation, and 2 days and 6 weeks after parturition). Tissues from the bladder and urethra were collected for electron microscopy, western blotting and immunostaining for caveolin-1 and caveolin-3, Results The bladder capacity was greater and the modified leak-point pressures lower in pregnant and 2-day postpartum rats than in virgin and Q-week postpartum rats. The residual volume was significantly higher in the pregnant group. Electron microscopy showed more sarcolemmal caveolae in the smooth muscle cells of both the bladder and urethra of virgin rats than in the other groups. Lipid droplets and subsarcolemmal mitochondria accumulated in pregnant and a-day postpartum rats. Caveolin-1 protein was detected in the cytoplasmic membrane of urethra and bladder smooth muscle cells. Caveolin-3 was detected in the membrane of striated muscle in the intrinsic sphincter. Western blotting showed increased caveolin-1 protein expression in the bladder and urethra of 2-day postpartum rats; in contrast, levels of caveolin-1 were lower in pregnant rats than in virgin and 6-week postpartum rats. Conclusions During pregnancy there was a significant decrease in sarcolemmal caveolae and caveolin-1 in the smooth muscle cells of the rat bladder and urethra. The changes in caveolae and the membrane protein caveolin may play a role in the functional changes associated with pregnancy and after delivery.