Incorporation of radioactive glucosamine into the serum proteins of intact rats and rabbits

Abstract

d-[i-¹⁴C]Glucosamine was administered to rats and rabbits by intraperitoneal injection in order to study the incorporation of hexosamines into the glycoproteins of liver and serum. Maximum radioactivity of the fraction soluble in trichloroacetic acid was found in rat livers within 30 min after injection and in rabbit livers within 1 h. Highest values for radioactivity in the trichloroacetic acid-insoluble fraction were found at 3 h for the rat. Maximum protein-bound radioactivity in the serum was found at 3 h for the rat and at 7 h for the rabbit. Efficient incorporation into serum proteins was found in both species, being 24 % and 28 % of the administered dose for rats and rabbits, respectively, at the maximum level of radioactivity. About 22 % of the bound radioactivity of serum was found associated with sialic acid in the rat, most of the remaining 78 % was associated with glucosamine, and only negligible amounts of radioactivity were found in the hexoses. Liver glycogen was not radioactive. Glucosamine was isolated from serum protein hydrolysates with the radioactivity in the number-one position. Therefore, it appears that parenterally administered glucosamine is incorporated into liver and tissue glycoproteins without degradation. The value of [i-¹⁴C]glucosamine as a tool for further studies of glycoprotein metabolism is indicated.