Rate of Initial Entry of Ca47 and Sr85 from the Intestine into the Vascular Space.

Abstract

The rate of initial entry of both radioactive Ca and Sr from the gastrointestinal tract into the vascular system was determined in man by adapting an integral equation approach for use with a digital computer. A single tracer dose of Ca47 and of Sr85 was given both by the oral and intravenous route in separate studies and serial samples of plasma were obtained for radioassay. The maximal rate of initial entry of Ca47 per 15-min. interval ranged from 2.2% to 3.8% of the dose and was reached within 1 1/2 hr. This rate was sustained for about 1 hr. and decreased thereafter with time. The rate of initial entry for Sr85 was less than that for Ca47, not exceeding 1.5% of the dose in any 15-min. interval, but was relatively more sustained from the 1st to the 4th hr. After the 4th hr., the rates of initial entry of Sr85 and Ca47 were almost proportional.