Relationship between Voided Urine Volume and Urinary ATP in Healthy Volunteers

Abstract

Purpose: We examined the relationship between the urinary ATP level and the desire to void, voided urine volume, and urinary osmotic pressure. Materials and Methods: The subjects were 4 healthy volunteers (2 men and 2 women) without micturition disorders who were not taking any medications and had normal urinalysis findings. Over 2 - 3 days, they urinated into a clean cup a total of 20 times. The strength of the desire to void was classified (none, slight, moderate, or strong; scored from 1 to 4, respectively) and a voiding score was assigned at each urination, along with measurement of the voided volume, urinary ATP, urinary creatinine, and urinary osmotic pressure (one man). Results: Variation of the urinary ATP/creatinine ratio was large in both male and female subjects. The urinary ATP/creatinine ratio was lower in the 2 men compared with the 2 women. This ratio showed a significant negative correlation (R 2 = 0.1577 and 0.1673, both p < 0.05) with the voided urine volume in the male subjects. However, there was no relationship between the urinary ATP/creatinine ratio and the voiding score or voided urine volume in the female subjects. Conclusions: The urinary ATP level may not be a clinically useful marker of bladder pathology. Both the present study and our previous studies identified a large sex difference in the urinary ATP/creatinine ratio, and this finding may be important when considering the causes of overactive bladder (OAB) in women. The mechanism underlying the increase in urinary ATP in women should be investigated to develop new therapies for OAB.