Effect of pregnancy on rabbit urinary bladder physiology. 1. Effects of extracellular calcium.

Recent advances in imaging technology have allowed for the diagnosis of many congenital urologic abnormalities through the use of antenatal ultrasonography. There is controversy in the literature as to whether antenatally detected dilatations of the urinary tract are always secondary to obstruction or if in select cases the dilatations are physiologic in nature and will spontaneously regress. Benign dilatations of the fetal urinary tract are postulated to be secondary to the increased fetal diuresis and a more compliant fetal urinary tract. No one has investigated the possibility that such dilatations might be a consequence of the hormonal changes seen with pregnancy. In this study we present evidence for a change in bladder function with pregnancy. A summary of our results shows that in the presence of bethanechol, strips from the urinary bladders of pregnant rabbits generate 50% less tension in response to calcium than those from nonpregnant rabbits. Such a suppression in smooth muscle function might also help explain the benign dilatations of the upper urinary tract which are seen frequently during pregnancy.