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Effect of ascorbic acid deficiency on the in vivo synthesis of carnitine.

The effects of ascorbate deficiency on carnitine biosynthesis was investigated in young male guinea pigs. Liver and kidney carnitine levels were not affected by the deficiency, but scorbutic animals had 50% less carnitine in heart and skeletal muscle than control animals. Labeled carnitine precursors, 6-N-tri-methyl-L-lysine and 4-N-trimethylaminobutyrate, both of which require ascorbate for their enzymatic hydroxylation, were injected into the vena cava of control, pair-fed and scorbutic animals. The distribution of isotope in compounds present in the liver and kidney after 1 h was determined. The uptake of trimethyllysine by the liver was less than 2% in 1 h, while the kidney took up approx. 20% of the 14C. Control and pair-fed animals converted trimethyllysine to kidney trimethylaminobutyrate 8--10 times as well as did scorbutic animals. Trimethylaminobutyrate hydroxylase, present in the liver but almost absent from the kidney, converted nearly all of substrate taken up by the liver to carnitine in both the scorbutic and control animals.

Animals↗

Alteration of bone status with ascorbic acid deficiency in ODS (osteogenic disorder Shionogi) rats.

Rats with hereditary defects in ascorbic acid (AsA) synthesis (ODS rats) subjected to AsA-deficiency for 3 weeks showed reductions of plasma alkaline phosphatase and dry and ash weights of the tibia, but no body weight alteration. In accordance with the chemical changes, bone loss and decrease of bone formation by AsA deficiency but not by malnutrition were observed in contact microradiographs of the tibia and by a tetracycline double labeling technique, respectively. The mechanical properties of femora measured by a three point-bending procedure were also altered by AsA deficiency for 3 weeks and showed decreases of 59% in toughness, 32% in strength, 32% in ductility and 22% in stiffness. The biomechanical changes by AsA deficiency were greater than the chemical changes in bone, indicating the usefulness of measuring mechanical properties as a sensitive method for the evaluation of the bone status. The second moment of the area of the femur was not changed by AsA deficiency. These results suggest that AsA deficiency in ODS rats causes marked bone loss and reduction in bone formation, which is accompanied by a greater reduction in biomechanics of the femur without causing macroarchitectural changes.

Animals↗

Multilocational hepatocyte transplantation for treatment of congenital ascorbic acid deficiency rats.

We attempted multilocational hepatocyte transplantation (HCTx) including hepatocyte-bearing polyurethane foam (PUF) to treat congenitally ascorbic acid (AsA) biosynthetic enzyme-deficient (ODS-od/od) rats. Hepatocytes isolated from the liver of congeneic rats were transplanted into the portal vein (Pv), spleen (Sp), omentum (Om), and mesentery (Ms). Hepatocyte-bearing PUF was transplanted into the Om and Ms. Experimental groups were divided into four groups (group I; Pv + Sp, group II; Pv + Sp + Om + Ms, group III; Pv + Sp + hepatocyte-bearing PUF, group IV; control). The average serum AsA level of the surviving rats in group II and III was significantly higher than that in group I 3 mo after HCTx. Histological examination showed small foci of surviving hepatocytes in the Om and Ms tissues and in the connective tissue in the PUF. ODS-od/od rats survived for a long time by multilocational HCTx.

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