Heterogeneity of glutathione synthesis and secretion in the proximal tubule of the rabbit

This study was designed to examine the synthesis and possible secretion of glutathione (GSH) in the S , S , and S segments of the rabbit proximal tubule. GSH synthesis and secretion rates were measured in the three segments of the proximal tubule, using the isolated perfused renal tubule technique. Tritiated ( H) glycine was perfused into segments and synthesized[Formula: see text]GSH ( H on the glycine residue) was measured in the bathing solution, collectate, and tubule extract. In the S segments, GSH was synthesized at the rate of 8.65 ± 0.88 fmol ⋅ min ⋅ mm tubule length and preferentially secreted into the lumen at the rate of 7.28 ± 0.74 fmol ⋅ min ⋅ mm . The difference between synthesis and secretion appeared in the bathing solution. The S segment synthesized GSH at the rate of 3.88 ± 0.82 and secreted GSH at the rate of 2.78 ± 0.57 fmol ⋅ min ⋅ mm . GSH synthesis and secretion rates in the S segment were 5.45 ± 1.19 and 4.22 ± 1.16 fmol ⋅ min ⋅ mm , respectively. Cellular concentrations of[Formula: see text]GSH increased along the length of the proximal tubule, with the highest concentrations in the S segment. The respective GSH cellular concentrations in the S , S , and S segments were 35.89 ± 10.51, 49.65 ± 9.32, and 116.90 ± 15.76 μM. These findings indicate that there is heterogeneity of GSH synthesis along the proximal tubule and that synthesized GSH is secreted preferentially into the lumen.