Influence of gender on the diurnal variation of urine production and micturition characteristics of the rat

The diurnal variation in the frequency/volume characteristics of male and f emale conscious rats was evaluated with reference to fluid consumption and urine production. Baseline values of the micturition volume and frequency o f nine male and 10 female SD adult rats were measured over a 24-hour time p eriod. The level of initial hydration conditions was standardized with 5 ml of water administered orally. With animals in a metabolism chamber having free access to water, the total volume of water consumed, the frequency/vol ume characteristics during micturition and the urine production rate were d erived from the measurements of voided volume as detected by a digital bala nce. To establish reliability of measurements two separate micturition stud ies were done per rat at an interval of 1 week. Mean frequency of micturiti on and mean volume voided per micturition and urine production rate were co mputed in 3-hour time bins and represented over the 24-hour period. In addi tion the mean values of the number of micturitions and mean micturated volu mes during the day/dark cycle were evaluated. The results how significant g ender specificity in water consumption, urine production, and diurnal varia tions in micturition frequency/volume characteristics. Females consistently consume significantly larger amounts of water (83%) than males while urine production rate was correspondingly higher in females. It is concluded tha t water consumption and urine production are gender-specific. Because highe r volumes of water are imbibed by females than males, the frequency/volume characteristic of micturition in the rat is also gender-specific. Data sugg est that the volume voided per micturition depends on the urine production rate. Neurourol. Urodynam. 20:287-295, 2001. (C) 2001 Wiley-Liss, Inc.