The changes in aldolase isoenzyme pattern during development of the human kidney and small intestine--demonstrated in organ extracts and tissue sections.

Aldolases A, B and C were determined by immunotitration analysis in extracts of human kidney and small intestine and demonstrated immunohistochemically in tissue sections of the same organs at various stages of development. By both techniques a change of isoenzyme pattern during development of the kidney and the small intestine was observed, leading from the predominance of A-type towards the predominance of B-type aldolase. In the extracts of kidney and small intestine the specific activity of aldolase B--but not that of aldolase A--rises with age by about one order of magnitude. The histochemical investigation showed that the developmental change in aldolase pattern in the organ extracts is caused by the differentiation of proximal tubulus cells in the kidney and the differentiation of epithelial cells in the small intestine. Within these cells an increase in the concentration of aldolase B and a decrease in that of aldolase A takes place during development. The possible physiological role of this cellular change in aldolase isoenzyme pattern is discussed. Aldolase C was found only in low concentrations in fetal organs. Only in the kidney, a specific localization within the proximal tubules could be demonstrated.