Renal micropuncture study of the effects of D‐glucose tubular calcium handling in the anaesthetized rat

Abstract

Tracer microinjection studies were used to grossly locate the nephron site of altered calcium transport following D-glucose loading. Superficial proximal and distal nephrons were injected with a solution containing 45Ca and either D-glucose or L-glucose (as control). Tubule calcium transport was assessed from the recovery of radioactivity in the final urine. 45Ca recoveries from early proximal microinjections were comparable in the two groups (2.63 +/- 0.68 vs. 3.70 +/- 1.19%). However, 45Ca recoveries from late proximal microinjections were significantly higher than D-glucose was included in the injectate (7.39 +/- 1.34 vs. 2.83 +/- 0.67%, P < 0.05). 45Ca recoveries from distal microinjections were also significantly higher in the D-glucose group (87.6 +/- 2.43 vs. 71.0 +/- 2.92%, P < 0.001). These data suggest that the effects of D-glucose on renal calcium handling are mediated at the level of the distal tubule, thick ascending limb of the loop of Henle and/or pars recta. The precise mechanisms involved are not known.