[Intestinal amino acid absorption in vitamin D dependent rickets]

Since structure and specifity of amino acid transport systems are basically similar in kidney and intestines it was suspected that rickets associated with hyperaminoaciduria was linked with defective intestinal amino acid uptake. Therefore amino acid absorption from everted sacs of small intestines was studied in 2 piglets suffering from vitamin D dependent rickets, and 7 healthy piglets using 14-C labelled amino acids. The experiments revealed an unaffected intestinal absorption in the rachitic animals, whereas the uptake decreased significantly with increasing age of the experimental animals. The results from these studies suggest that regulatory factors in the blood system, e.g. increased level of PTH or lack of specific vitamin D metabolites, do not directly affect amino acid transport systems in kidney and intestines. It is concluded that hyperaminoaciduria has to be mediated through specific and thus far unidentified effects at the tubular cell level.