On the Incorporation of Radiosulfate in the Cartilage

Journal/Book: Separatum E X P E R I E N T I A BIRKHÄUSER VERLAG BASEL SCHWEIZ Vol. XI/2 1955 - pag. 65. 1955;

Abstract: Institute of Human Anatomy University of Turin August 31 1954. DZIEWIATKOWSKI et al.1 showed that radioactive sulfur administered intraperitoneally to 7 days old rats becomes fixed in a high proportion in the hyalin cartilage of the skeletal anlagen. DZIEWIATROWSKI and later BOSTRÖM gave the further proof that the radiosulfate is incorporated in the chondroitinsulfuric acid; uptake of radiosulfate was also demonstrated in a mucopolysaccharide fraction isolated from rats skin. Besides BOSTRÖM and MÅNSSON have shown that the radioactive sulfur is taken up by slices of hyalin cartilage (e. g. fresh rib cartilage of adult calves cats and guinea pigs) suspended in Krebs solution and that it is introduced into the chondroitinsulfuric acid during its synthesis : the possibility that in the absence of an enzyme system an exchange reaction of the sulfate group might occur was disposed of. According to BOSTRÖM and MANSSON exchange does not take place even in solutions of pure chondroitinsulfuric acid alone. The data presented here offer evidence that also in the living animal the fixation of radiosulfur to cartilage depends upon processes of synthesis and that a simple exchange of radiosulfate with the sulfate group of the chondroitinsulfuric acid does not occur to any autoradiographically detectable extent. The following results are part of an autoradiographic study an the distribution of radiosulfur in the differentiation and growth of cartilage in chicken embryos. The technique of the experiments and a summary of the main results have been presented elsewhere; here we only want to stress the fact that in given regions of the cartilage in which large amounts of chondroitinsulfuric acid are available for sulfate exchange but no actual increment of the matrix occurs no fixation of radiosulfur takes place. By treating chicken embryos of various ages with small amounts of S35-labeled sodium sulfate (e.g. 5 to 10 µC) different results are obtained according to whether the embryos are fixed from 2 to 10 h or from 5 to 10 days after the treatment. In short term experiments only the matrix which formed or underwent increment during the period of treatment shows a varying degree of radioactivity. In long term experiments especially if the treatment with radiosulfate is started before the beginning of chondrification of the cartilaginous anlagen (viz. in the 4th or 5th day of incubation) the whole cartilage of the skeletal pieces appears radioactive (Fig. 1) ; however differences in the degree of radioactivity are apparent between different cartilaginous segments or from region to region of the same skeletal element according to the degree of their histological differentiation. ... ___MH

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