Abstract

The choline metabolite betaine has been shown to be an important organic osmoregulatory solute in the kidney. The isolated perfused rat kidney and kidney slice incubations were used to investigate the effect of 2-dimethylaminoethanol (DMAE), a choline oxidase inhibitor, on the renal excretion and metabolism of choline. In the isolated perfused kidney, [14C]choline, at an initial perfusate concentration of 300 microM, was effectively removed from the perfusate over 25 min, with nearly all the 14C in the perfusate accounted for by betaine during the remainder of the 90-min perfusion. DMAE at concentrations of 3.0 or 5.0 mM significantly decreased the rate of removal of [14C]choline from the perfusate and the rate of addition of [14C]betaine to the perfusate, yet [14C]betaine remained the only metabolite of choline in perfusate and urine. In kidney tissue slice experiments, conversion of [14C]choline to [14C]betaine was found in cortical, outer medullary and inner medullary regions of rat kidney. DMAE at 5.0 mM significantly inhibited [14C]betaine production in each of the three regions studied. These data show that DMAE is an effective inhibitor of betaine production by the kidney and, as such, may be an important agent for the study of osmoregulation by the kidney.