Comparison of intravenous infusion of stable strontium with the calcium tolerance test.

Abstract

Data obtained by the calcium tolerance test (Ca TT) were compared with those obtained with the intravenous administration of an equivalent amount of stable Sr in 9 human subjects. Urinary Ca excretion increased in all subjects on the day of Sr (977 mg) infusion. The sum of the increase plus the amount of Sr excreted equaled the amount of the excess urinary Ca observed on the day of the Ca TT. In all subjects the percentage of Sr excreted was always less than that for Ca. On the days following the infusion, the elimination of Sr decreased exponentially from the 24th or 48th hr. After 7 days, the total quantity of Sr eliminated was between 6 and 43% of the administered dose. Plasma Sr levels rose gradually, reaching at the end of the infusion a peak of 10% of the infused dose per total plasma volume and declined thereafter with time. Plasma levels of Ca also increased, reaching a peak at the second hr and returning to the control values in 6 to 8 hr. From these results, it appears that the sum of the increased calciuria and of the Sr excretion, similarly to the excess calciuria following the Camore » TT, are an indication of the skeletal capacity to retain Ca. Moreover, the ratio of Sr excretion to the increase in calciuria on the day of Sr infusion was an index of the magnitude of the exchangeable pool. It appeared that Sr has the same effects as Ca on the parathyroid glands, and that its metabolism is controlled by the same homeostatic mechanism as that of Ca. (TCO)« less