Mechanism For Exercise-induced Diuresis Observed Following An Exhaustive Short Duration Run

Abstract

PURPOSE: Reductions of renal plasma flow (RPF) and glomerular nitration rate (GFR) after an exercise are depending on an increasing workload. However, an excessive increase in urine flow rate (UFR) was observed 15 to 30 min after exhaustive exercise. This phenomenon is called exercise-induced diuresis (EID). The mechanism for EID remains unclear. Recent studies have suggested that the regulation of GFR might be due in part to a change in the luminal Cl via the maculadensa. The present study was conducted to ascertain the relationship between changes in UFR and urinary Cl concentration following a 400m exhaustive run, and to consider the mechanism for EID. METHODS: Eight healthy male volunteers performed an exhaustive run twice with a 60 min interval. Urine samples were taken both at 15 and 30 min before, immediately after as well as 15, 30, 45 and 60 min after the 400m exhaustive run. UFR and urinary Cl, Na, creatinine (cr), lactate (uLa), pyruvate (uPa) and osmolality (Uosm) were measured. Blood samples were taken before, immediately after, and 30 min after the run. Serum electrolytes, cr and Sosm, lactate (bLa), pyruvate (bPa) and plasma ADH, aldosterone (pAld), and catecholamine concentrations were measured. Creatinine clearance (Ccr) was calculated as the indicator of GFR. RESULTS: Fifteen to thirty min after the run, UFR increased 2∼4.4 fold, and Uosm decreased to 35∼25% of the pre-run level. Ccr decreased to 62∼70% of the resting level immediately after, and gradually recovered. Urinary Cl concentration decreased to 11.7 and 7.8 %, in contrast to only 83.5 and 91.3 % of the resting level in Na concentration, at 15 and 30 min after the run. The remarkable reduction of urinary Cl concentration was accompanied by an increase in uLa following the 400m exhaustive run (r=−0.887, p<0.001). La and Pa might be preferentially excreted into urine over Cl. The remarkable reduction in Cl concentration in urine might have a role in compensating for the increase in the anion gap in urine produced by the 400m exhaustive run. CONCLUSIONS: The decrease in Cl in the distal tubule might reduce the contraction of the mesangial cells via the macula densa, and might lead to an increase in GFR (Ccr) and UFR.