Sulfate Metabolism in Rat Calvaria Cultured Under Vitamin A Deficient Conditions

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; X +/- 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; X +/- 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 defect in the degradative process.