3H-thymidine uptake by the rat urinary bladder after induction of diabetes mellitus

Streptozotocin-induced diabetes mellitus causes diuresis, increases in bladder mass and changes in micturition. Temporal changes in micturition and bladder mass after induction of diabetes with streptozotocin were monitored and correlated with DNA synthesis and 3H-thymidine incorporation. There were increases in water consumption, urine excretion, urinary frequency, and mean and maximal micturition volume within 1 day after induction of diabetes. These parameters reached maximal values within 6 to 11 days and were maintained at 30 and 60 days. Bladder mass was significantly elevated by 7 days and did not increase further with increasing duration of diabetes. DNA concentration was decreased in bladders from 4, 7 and 14 day diabetics. 3H-thymidine incorporation into DNA increased within 2 days after induction of diabetes, reached maximal values at 4 to 7 days and declined to control values by 14 days. Autoradiography showed intense labelling of the urothelium one day after induction of diabetes, with labelling remaining high up to day 7. Connective tissue and smooth muscle labelling were slower to develop. Labelling of smooth muscle was transient, appearing only on days 4 and 7. The time course of the events was consistent with the hypothesis that bladder distension or increasing micturition volume stimulates thymidine incorporation into DNA, resulting in an increase in bladder mass.