Abstract

The cells of the inner medulla of the mammalian kidney accumulate high concentrations of nonurea organic osmolytes. The organic osmolytes found in the kidney include glycine betaine and sorbitol. This study was designed to measure changes in the urinary excretion of glycine betaine and sorbitol and the plasma concentration of glycine betaine in response to an acute water load (20 ml/kg) or acute water deprivation in young healthy males. In response to a water load the urinary excretion of glycine betaine and sorbitol increased parallel with or shortly after urinary urea excretion. The increase in urinary urea and sorbitol excretions preceded maximum minute volume, whereas peak glycine betaine excretion was closely related to maximum urine minute volume. Subsequently, urea, sorbitol, and glycine betaine excretion rates returned to baseline. In contrast, during water deprivation no change in glycine betaine, sorbitol, and urea urinary excretions occurred during the study period. Plasma glycine betaine concentration was stable during both diuresis and antidiuresis. We conclude that the organic osmolytes glycine betaine and sorbitol are components of a physiological and dynamic system in response to an acute water diuresis.