Sulfate Metabolism in Rat Calvaria Cultured Under Vitamin A Deficient Conditions

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Abstract
The metabolism of sulfated glycosaminoglycans (GAG) in bone has been found to be altered in vitamin A deficiency. A neonatal rat calvarium model system was used to determine if these changes are related to catabolic defects. Two day old rat pup calvaria were cultured in media containing serum from A — or A+ rats and radiolabeled sulfate or glucosamine. The incorporation of 35S-sulfate into the GAG fraction of calvaria cultured with A — serum for 48 hours was significantly increased compared to the values found in calvaria cultured with A+ serum (A —, 1,970 ± 300; A+, 940 ± 177; x̄ ± SD). The uptake of 35S-sulfate into the GAG fraction of calvaria cultured with A- serum showed continuous increase over 96 hours, whereas, 35S-sulfate uptake leveled off after 24 hours in the A+ group. There was also a significant increase in [14C]glucosamine uptake into the GAG fractions of calvaria cultured with A — serum (A —, 1,966 ± 537; A+, 1,662 ± 244; x̄ ± SD). To determine if the alteration in metabolism of sulfated GAG was in the biosynthetic or degradative pathways, a chase study was performed in which the calvaria were prelabeled with 35SO4. The rate of tissue loss of 35S-sulfate was lower in the total digests and the GAG fractions from calvaria cultured with A — serum than those cultured with A+ serum. Thus, the alteration in the metabolism of the sulfated GAG resulting from A — culture conditions seems to be a defect in the degradative process.