RENAL DISCRIMINATION BETWEEN CALCIUM AND STRONTIUM
The ratio of excreted (Sr/sub u/) to filtered (Sr/sub o/) radiostrontium (Sr/sup 85/) was compared with the ratio of excreted (Ca/sub u/) to filtered (Ca/ sub o/) calcium in human subjects and dogs undergoing a variety of diuretic procedures. The relation Sr/sub u//Sr/sub o/ = (Ca/sub u/,/Ca/sub o//sup 0.7/ serves to predict Sr/sub u//Sr/sub o/ from Ca/su b u//Ca/sub o/with a standard error of estimate of 15% over a wide range of variation (30- to 200-fold) in the 2 quantities. The equation can be derived from the assumptions that the 2 ions are reabsorbed at rates proportional to the local concentrations in the tubular fluid, and that the rate constant for Sr reabsorption is always 0.7 times that for Ca reabsorption. This relation was not affected by adrenocortical activity (in man), parathyroid activity, hypercalcemia, acid-base balance, Mg clearance, or diuretics (chlorothiazide or hydrochlorothiazide). Sulfate or ferrocyanide infusion was also without effect, presumably because the affinity of each of the 2 anions for Ca is similar to its affinity for Sr. Citrate, which binds Ca more strongly, diminishes renal discrimination between Ca and Sr. Although this relation has high predictive value (r* = 0.98), it does not establish that the reabsorption of Ca and Sr are first-order processes nor that the 2 ions share a common mechanism. (H.H.D.)
- Research Organization:
- Johns Hopkins Univ., Baltimore
- NSA Number:
- NSA-17-019760
- OSTI ID:
- 4726704
- Journal Information:
- Bulletin of the Johns Hopkins Hospital (U.S.), Journal Name: Bulletin of the Johns Hopkins Hospital (U.S.) Vol. Vol: 111; ISSN BJHHA
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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