Extrarenal handling of phosphate: effect of thyroparathyroidectomy, 1,25-dihydroxycholecalciferol, and dietary calcium.

It is known that 1,25-dihydroxycholecalciferol [1,25(OH)2D3] mobilizes inorganic phosphate (Pi) from gut and bone, thus increasing the entry of Pi into the extracellular space (ECS). In this work, we have investigated whether 1,25(OH)2D3 could also facilitate the net exit of Pi out of this pool into certain soft tissue and/or bone compartments in thyroparathyroidectomized (TPTX) rats. Sham-operated, TPTX, and TPTX rats treated with 1,25(OH)2D3 (26 pmol/day ip for 1 wk) were infused with a known amount of Pi over a given time.

Renal transport of bisphosphonates: accumulation by renal cortical slices enhanced by calcium phosphate ions.

Bisphosphonates have been recognized as useful therapeutic agents in metabolic bone disease. Earlier studies showed a net renal secretion of 1-hydroxy-ethylidene-1,1-bisphosphonate (HEBP). They suggested a renal cellular uptake of this compound.

In vivo determination of intestinal calcium absorption, with scandium-47 used as marker.

The 47scandium/47calcium ratio technique for studying intestinal absorption of calcium in humans offers the following advantages: neither blood sampling nor complete faecal collection are required, and there is no need for an additional marker or for knowledge of the precise dose of calcium isotope administered. In the study this technique was corrected and modified using a new equation that considerably simplifies the determination procedures. The new method was validated in rats with various intestinal calcium absorption rates.