Distribution of absorbed strontium-85 and calcium-45 as influenced by lactose

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Abstract
Studies on the absorption and subsequent deposition in bone of Sr85 and Ca45 injected into ligated sections of small intestine of the rat showed that: a) more Ca45 than Sr85 was absorbed from the intestine; b) especially during the 1st 4 hr, significantly more of the absorbed Sr85 than Ca45 was deposited in bone; c) injection of lactose, lysine, or glucose into the ileum, along with the alkaline earths, caused the absorbed Ca45 to deposit in the bone at the same rate as the Sr85, and also caused an increased total absorption of both radionuclides; these observations did not hold for the duodenum or jejunum, confirming differences in mechanism among the sections of the small intestine. Tentative explanations are suggested, the most plausible one being that calcium is bound as it is absorbed from the small intestine and that the presence of lactose in the intestine inhibits the production of the bound form.