Renal and bone uptake of tartaric acid in rats: comparison of L(+) and DL-Forms

Plasma concentrations of radioactivity declined biphasically with half-lives of about 15 and 58 h respectively in rats dosed with monosodium DL-[14C]tartrate for 7 days at a dose level of 2.73 g/kg/day. Uptake and retention of radioactivity occurred in blood cells, kidneys and bones where it was detected for at least 12 days after dosing. Renal retention (11202 +/- 4469 ppm at 6 h, n = 7) was probably due to precipitation of the poorly soluble calcium DL-tartrate in the tubules leading to increased kidney weight, nephrotoxicity and even death. The more soluble, naturally-occurring L(+)-[14C] tartrate was not retained in the kidneys (1287 +/- 118 ppm at 6 h, n = 8) when administered to rats under the same conditions, and the initial decline of plasma concentrations of radioactivity was more rapid (t 0.5 approx. 3 h). For this reason, monosodium L(+)-tartrate was non-toxic at 2.73 g/kg/day whereas monosodium DL-tartrate was toxic at this dosage.