1. The influence of thyroparathyroidectomy and/or acidosis on renal function and specifically on acid excretion was studied in rats treated with a cumulative dose of 2 mg of aluminium.
2. Aluminium-treated and non-treated thyroparathyroidectomized rats showed a significant decrease in glomerular filtration rate and in the urinary/plasma inulin ratio without alteration in net acid excretion.
3. Non-treated thyroparathyroidectomized acidotic rats showed a significant fall in the amount of ammonium excreted and in overall acid excretion, suggesting that parathyroid hormone participates in an important way in the defence against metabolic acidosis.
4. The effects of acidosis, thyroparathyroidectomy and aluminium treatment on renal function parameters were not additive, suggesting a common final mechanism. In normal or acidotic aluminium-treated rats, thyroparathyroidectomy had no effect on renal acid excretion, suggesting that aluminium even in low doses inhibited the action of PTH on the renal tubule.
5. After exposure to aluminium, the relative inhibition of PTH on the renal tubule may become an additional factor that could contribute to the worsening of clinical conditions in which an inappropriate retention of acid loads can occur.