Reliable information on the renal handling of aluminium (Al) is sparse, owing partly to uncertainties concerning its filterability and partly to the absence of a systematic micropuncture investigation. Here we report the results of a micropuncture assessment of Al filtration and also of its handling in the proximal convoluted tubule and loop of Henle.
Male Munich-Wistar rats were anaesthetized with Intraval (May & Baker; 100 mg kg-1, I.P.) and prepared surgically for micropuncture of the left kidney. They were infused I.V. with 0.9 % NaCl solution containing [3H] inulin and aluminium chloride in 3 % sodium citrate solution (400 µg Al bolus, 10 µg Al min-1), resulting in a plasma Al concentration of 5.4 ± 0.3 µg ml-1 (mean ± S.E.M.). Timed tubular fluid collections were made from Bowman’s space, late proximal convolutions and early distal tubules, and samples were diluted 150- to 300-fold prior to measurement of Al by electrothermal atomic absorption spectroscopy. At the end of each experiment, the rat was killed with an overdose of Intraval. The micropuncture results are shown in Table 1.
The results indicate that, contrary to conclusions reached using artificial filtration membranes (Lote et al. 1992), Al is freely filtered into Bowman’s space. No evidence was obtained for significant Al reabsorption in the proximal convoluted tubule, but substantial Al reabsorption occurred in the loop of Henle.
This work was supported by the National Kidney Research Fund.
- Lote, C.J., Wood, J.A. & Saunders, H.C. (1992). Clin. Sci. 82, 13-18.