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. The value of scandium as an unabsorbed intestinal marker was confirmed by the use of 46scandium. A mean recovery of 96% was obtained after intragastric administration. The 47scandium/47calcium ratio technique gave results that correlated well with the faecal 47calcium recovery method over a wide range of intestinal calcium absorption rates obtained by treatment with 1,25-dihydroxycholecalciferol or 1-hydroxyethylidene-1,1-biphosphonate. Taking into account the advantages of the 47scandium/47calcium ratio technique, it appears useful not only in small animals but also in outpatients, particularly children.