The Physiological Behavior of Calcium in the Rat

Abstract

The excretion, absorption and movement in the body of calcium as a function of age has been studied in 141 individual rats. Consideration was given to the use of radiocalcium data for the interpretation of the physiological behavior of the stable calcium normally present in the animal body, and the fundamental importance of balance data in radioisotope investigations was emphasized. Calcium absorption, retention and excretion rate were greatest in young animals, decreased rapidly to the age of sexual maturity and more slowly to maturity and old age. Daily endogenous fecal calcium losses and the requirements for maintenance increased slightly to maturity and markedly in the aged animal. Tissue calcium-45 concentration data, corrected for body weight and absorption differences due to age indicated that tissue deposition reflected the physiological status of the animal and its ability to handle the current calcium supply. The significance of fecal calcium partition, the estimation of endogenous calcium, true digestibility, maintenance requirements and the interpretation of radiocalcium data in terms of the behavior of stable calcium in the animal body are discussed.