Effects of thyroparathyroidectomy, phosphate depletion and diphosphonate therapy on acute uraemic extra-osseous calcification in the rat.

1. The effects of acute uraemia on arterial and visceral calcium concentrations were studied in acutely uraemic rats. The influences of thyroparathyroidectomy, phosphate depletion and diphosphonate therapy on extra-osseous calcium concentrations were assessed in this model. 2. Aortic and visceral calcium concentrations were greater in acutely uraemic rats than in non-uraemic rats. Both prior thyroparathyroidectomy and prior phosphate-depletion resulted in lower aortic and visceral calcium concentrations in non-uraemic rats and prevented the increase in aortic and visceral calcium concentrations with acute uraemia. Diphosphonate given for 5 days before and for 2 days after the induction of acute uraemia resulted in lower tissue calcium concentrations than in non-diphosphonate-treated acutely uraemic rats. In contrast, diphosphonate given only immediately before or only after induction of acute uraemia did not prevent the increase in extra-osseous calcium concentrations with acute uraemia. 3. It is concluded that acute uraemia results in an increase in arterial and visceral calcium concentrations. Both thyroparathyroidectomy and phosphate depletion are effective in preventing the increase in extra-osseous calcium concentrations in acute uraemia. Diphosphonates may have a future role in preventing such calcification.