PHOSPHORUS METABOLISM OF THE ADRENAL GLAND: THE MECHANISM OF THE CHANGE AFTER HYPOPHYSECTOMY
The specific activity of the intracellular inorganic phosphate (P) of the adrenal gland relative to that of the inorganic P of the plasma is significantly decreased in hypophysectomized rats at time intervals as long as 16 hr. after the injection of inorganic P labelled with P32. The specific activity of the intracellular inorganic P was determined (1) by measuring the specific activity of the easily-hydrolyzable acid-soluble P, which rapidly comes into isotope equilibrium with the intracellular inorganic P, (2) by calculation, from the specific activity of the inorganic P of the whole adrenal, assuming values for the specific activity and the concentration of the inorganic P of the extracellular fluid and the volume of the extracellular fluid compartment, and (3) by measuring the specific activities of the inorganic P of both the adrenal gland and the plasma at a series of time intervals after the injection of the P32. It is concluded that the decrease in the relative specific activity of the intracellular inorganic P of the adrenal is the result of a slowing in the passage of inorganic P32 across the cell membrane, i.e. from the extracellular to the intracellular fluid.