REMOVAL OF Ca40AND Ca45FROM BONE BY CITRATE AS INFLUENCED BY THE PARATHYROIDS1

Abstract

The effects produced by the introduction of exogenous citrate in a neutralized rinsing fluid into the peritoneal cavities of nephrectomized and para-thyroidectomized-nephrectomized male rats were followed through the technique of peritoneal lavage. Both groups of animals showed progressive increases in wash calcium when as little as 15 to 25 mg of citric acid were added per 100 ml of rinsing fluid. Peritoneal equilibration for one and one-half hours instead of one hour increased the amounts of calcium removed in the wash. Parathyroidectomized rats given the same amounts of citrate as control rats showed lower total wash calcium values; however, the increases in both groups were relative when compared to their citrate-free rinse values. The addition of citric acid did not appreciably alter the amount of radiocalcium removed in the wash when the radioactivity was administered within twenty-four hours of the start of the lavage. Therefore, because of the increase in the total calcium removed, the specific activity of the radiocalcium in the peritoneal wash fell markedly following the citric acid administration. These experiments are interpreted as showing that citric acid mobilizes calcium from the deep areas of bone, as does the hormone of the parathyroids, and not from those areas which are in close contact with the extracellular fluid compartments. No explanation of this phenomenon can be given as yet.