Developmental changes in normal fetal bovine whole bladder physiology.

In the present study, normal and experimentally altered whole fetal bovine bladders have been used in vitro to study developmental changes in compliance and capacity. For the first time, we have attempted to define the relative contributions of the detrusor and mucosal layers to bladder compliance. Fetal bovine bladder compliance increases with fetal development. Elimination of the active component of smooth muscle tension improves compliance and increases capacity more than 60% in younger fetuses but only 35% in older fetuses. Active smooth muscle tension as evaluated by whole bladder cystometry is highest in the youngest fetuses and decreases with fetal age. Surgical removal of the detrusor layer (smooth muscle and connective tissue) also increases compliance and capacity substantially in all fetal bladders. These observations show that both smooth muscle and connective tissue are important in the function of the developing fetal bladder. Changes in both of these bladder wall components probably occur during development and are responsible for the physiologic changes observed.