A simplified method for the determination of intestinal calcium absorption

The double-isotope technique for the estimation of intestinal calcium absorption was simplified by using the scintillation liquid Insta-Gel. The urine was mixed with Insta-Gel without any previous preparation. A suitable constitution of the sample was ascertained by preliminary experiments (1 ml urine + 10 ml Insta-Gel); the stability of the samples, the correctness of 45Ca (counting separately as well as mixed with 47Ca) and the linearity of the counting rates of 45Ca obtained in a range of doses over four orders was proved. In 43 subjects aged 20 to 65 years and without any disturbance of calcium metabolism or intestinal function, the average normal value of fractional calcium absorption was 45.9 +/- 1.6% (SEM).