INTESTINAL STRONTIUM ABSORPTION - FROM BIOAVAILABILITY TO VALIDATION OF A SIMPLE TEST REPRESENTATIVE FOR INTESTINAL CALCIUM-ABSORPTION

Calcium absorption tests have rarely been validated for being represen tative for absolute bioavailability (true absorption) or for intraindi vidual variation. Therefore, we investigated the reproducibility of th e absolute bioavailability of strontium chloride, a marker for intesti nal calcium absorption, in healthy male volunteers (n = 8) by measurin g the area under the plasma strontium concentration-time curve after o ral and intravenous administration of strontium. Subsequently, we sele cted a simple test variable as being representative of absolute bioava ilability. The mean absolute bioavailability (+/-SD) was 25% +/- 7%. T he best test variable appeared to be the fractional absorption at 240 min (Fc(240)) after oral intake, which demonstrated the highest correl ation with absolute bioavailability (r = 0.66). The intraindividual va riations of the data for this variable and for the absolute bioavailab ility are similar to those described for various absorption tests base d on the use of calcium isotopes. Thus, the Fc(240) of strontium offer s the potential of a simple clinical test for use as a measure of inte stinal calcium absorption and its modulation.