dolichol-monophosphate-mannose and Body-Weight

The effects of protein malnutrition during the nursing period on glycoprotein biosynthesis by testes of 20-day-old rats was studied. Pregnant Wistar rats were housed individually. On the day of delivery they were divided into two groups: one was fed a control diet (25% casein) and the other a low-protein diet (8% casein) for a period of 20 days. Body and testis weights of pups suckled by the malnourished mothers were significantly lower than those of the pups suckled by normally-fed mothers. The seminiferous tubules o malnourished rats showed a significant decrease in diameter and in the stage of development of spermatogenesis. Whole testes of normally-fed 20-day-old rats showed significantly greater [2-3H]mannose incorporation into glycoproteins than did the testes of malnourished rats of the same age. The microsomes of normally-fed rats showed significantly higher GDP: mannose polyprenyl mannosyl transferase activity than did microsomes from malnourished rats, and this difference increased when exogenous dolichyl-phosphate was added to the incubation medium. These results indicate that protein malnutrition decreases GDP: mannose polyprenyl mannosyl transferase activity in the microsomes of testes from 20-day-old rats.

Topics: Animals; Animals, Suckling; Body Weight; Dolichol Monophosphate Mannose; Glycoproteins; Male; Microsomes; Organ Size; Protein Deficiency; Rats; Rats, Inbred Strains; Testis

Studies were conducted to investigate the in vivo and in vitro effects of retinol and retinoic acid on the synthesis of mannolipids and mannopeptides in rat liver. The incorporation of 14C-mannose into glycolipids and glycoproteins showed a decrease in vitamin A-depleted rats as compared with vitamin A-fed rats. By means of DEAE-cellulose, silicic acid and thin-layer chromatography, the mannose-containing lipids were separated into mannosyl retinyl phosphate (MRP, Rf 0.2) and dolichyl mannosyl phosphate (DMP, Rf 0.4), respectively. A rapid increase in the synthesis of labelled MRP was observed, exhibiting a peak between 25 and 60 min after intraperitoneal administration of retinol to vitamin A-depleted rats. Similarly, administration of retinoic acid brought about elevation of 14C-mannolipid (Rf 0.2) synthesis with a peak at 60 min after injection. On the other hand, the incorporation of 14C-mannose into DMP (Rf 0.4) remained unchanged by such treatment. In vitro addition of retinyl phosphate, but not retinoyl phosphate, markedly stimulated the synthesis of 14C-mannolipid (Rf 0.2), using crude membrane of rat liver and GDP-14C-mannose as the donor. These findings strongly suggest that not only retinol but also retinoic acid plays an important biological role in mannosyl transfer reaction in rat liver. However, the molecular participation of a metabolite of retinoic acid in the formation of a mannolipid and the structure of such a metabolite remain to be established.

Topics: Animals; Body Weight; Dolichol Monophosphate Mannose; Glycolipids; Glycopeptides; Glycoproteins; In Vitro Techniques; Liver; Male; Mannose; Mannosyltransferases; Polyisoprenyl Phosphate Monosaccharides; Polyisoprenyl Phosphate Sugars; Rats; Tretinoin; Vitamin A; Vitamin A Deficiency