Tissue calcification and alkaline phosphatase activity in uraemic rats.

The activity and localization of alkaline phosphatase activity (AP) in aorta and heart, and the incidence of calcifications in aorta, heart and kidney as well as cardial fibrosis were studied in uraemic rats treated with 1,25-dihydroxycholecalciferol (1,25-DCHH) and Nifedipine. 1,25-DHCC treatment elevated the serum Ca x P product and aggravated the development of renal and aortic calcifications and cardial fibrosis. Nifedipine did not protect against calcifications, but decreased the incidence of cardial fibrosis. The activity of AP was increased in the thoracic aorta in uraemia independent of 1,25-DHCC or Nifedipine treatment or presence of calcification. No changes of the AP activity were found in the heart.