QUANTIFICATION OF NORMAL AND ADRENAL STEROID AFFECTED CALCIUM METABOLISM IN THE YOUNG DOG

¹ Research Laboratories, The Upjohn Company, Kalamazoo, Michigan
² Research Laboratories, The Upjohn Company, Katamazoo, Michigan

Adrenal steroid increased the total calcium content of the compartment associated with blood serum in young beagle dogs. This increase was reversed on cessation of steroid regimen. Blood serum and fecal calcium were invariant during the intervals where Ca⁴⁷ distribution was studied in pre-, post- and steroid phases after intravenous administration. This was indicative of the relative constancy of the calcium pool sizes or compartmental volumes during the times of radioisotope study.

There was no significant variation of calcium values in serum or feces, Ca⁴⁷ excretion or kinetic constants of Ca⁴⁷ elimination from the blood serum with steroid dose levels of 0.50 to 2.00 mg/kg/day/dog. This indicated a physiological attitude on chronic administration which was not dose-responsive in these dose ranges.

The age of the young beagle significantly affects calcium metabolism with significantly less incorporation of calcium into a "deep compartment" and significantly more fecally excreted.

From the calcium data and Ca⁴⁷ kinetics, estimates have been made of calcium in the various compartments of an operational model and the rates of transfer among these compartments. The data are consistent with a transfer of serum calcium initially into the extracellular body water and subsequently into a compartment that may be associated with a metabolic precursor to bone possibly in part the protein matrix. Adrenal steroid regimen inhibits the capacity of this compartment and the rates of transfer into a deep compartment which may be synonymous with "bone." On cessation of steroid, this phenomenon tends to reverse although the steroid effects appear to have persistence.