P 32 Localization in the Intestine

Abstract

Radioautographic and histochemical observations have been made on sections of frozen-dried rat and mouse intestine containing P³². The tissue sections were prepared and mounted and radioautographs were made using procedures reported previously( 1 , 2 ). These procedures are designed toward qualitative and quantitative preservation and retention at the original sites of tissue constituents. The radioautographs of rat and mouse duodenum and small intestine have shown a more striking concentration and localization pattern with P³² than has been observed for other soft tissues. This localization occurs in the glands of the mucosa with the greater concentration at the more basal groups of cells (Fig. 1).

Studies of the solubility of localized P³² frozen-dried sections of rat intestine have been reported( 3 ). The localized P³² exhibits the same general solubilities as the background P³² in other regions of the tissue, indicating a similar chemical form. The P³² is not in phospholipid form as it does not dissolve in organic solvents; other solubility tests have indicated the presence of free phosphate ions and at least a partial protein linkage. The use of formalin or Bouin's solution as a fixative results in a radioautograph showing the same general type of localization pattern, but of diminished intensity as compared to the results with frozen dried tissues. This would be expected on the basis of solubility data.

Observations made at varying time intervals from isotope administration to killing the animal have shown that the typical localization pattern is present in the intestine at 30 believe that this evidence identifies the P³² with that which is being incorporated into newly formed desoxyribose nucleic acid molecules in the rapidly dividing mucosal cells. However, from a quantitative standpoint, chemical analyses( 4 ) have shown that the P³² incorporated into newly formed nucleic acid is only a minor fraction of the total intestinal P³² uptake.