Administration of isolated chicken L-gulonolactone oxidase to guinea pigs evokes ascorbic acid synthetic capacity

Assisted Enteral Feeding of Exotic Companion Animals

Malnutrition is a known concern during hospitalization for humans, dogs, and cats. The same nutrition principals to reduce the risk of malnutrition can be applied to exotic companion animal patients. However, it's important to understand that many nutritional requirements are ill defined for specific species and prudent clinical judgment is required.

Administration of gulonolactone does not evoke ascorbic acid synthesis in teleost fish

Evidence is presented that for common carp (Cyprinus carpio L.), intraperitoneal injection of L-gulonolactone, a precursor of ascorbic acid synthesis in the D-glucuronic acid pathway, does not result in an increased concentration of ascorbate in tissue. Control fish injected with an equimolar amount of ascorbic acid have shown a significant increase in ascorbic acid concentration in the kidney, hepatopancreas, plasma and spleen. The ascorbate status in the carp body,i.e., the ascorbate nutritional history, produced significant differences in ascorbate withdrawal from circulation and probably in the catabolic rate. Acute fasting decreased ascorbate uptake into tissues as compared to fish fed a diet lacking ascorbate. Intraperitoneally injected ascorbate affects common carp being fed a diet containing 295 mg of total ascorbic acid kg(-1) by causing tissue to become saturated with vitamin C, similar to the tissues in the group undergoing acute fasting. There was no gulonolactone oxidase activity in the hepatopancreas of the common carp. These results suggest that the metabolic rate induced by feeding is the primary factor regulating ascorbate requirement.

Biosynthesis of ascorbic acid in chick embryos

Biosynthesis of ascorbic acid was found in the kidneys (mesonephros and metanephros) of the chick embryo as well as in the yolk sac membrane. The activity of L-gulonolactone oxidase in the yolk sac membrane suggested that it was the major source of ascorbic acid in the chick embryo.

Glutaraldehyde-reacted immunoprecipitates of L-gulonolactone oxidase are suitable for administration to guinea pigs

The potential pharmacologic use of enzymes has long been considered. Practical applications, however, have been limited by the toxicity and allergic response to administered foreign proteins. A simple in vitro modification that allows the intraperitoneal administration of large doses of L-gulonolactone oxidase to guinea pigs is described. The enzyme is precipitated by guinea pig antisera and reacted with glutaraldehyde (0.125%). The product is comparatively nontoxic in guinea pigs. Administration of this enzyme enables guinea pigs to synthesize ascorbic acid. Success of this approach may depend on reinforcement by the bifunctional reagent of the enzyme-antibody complex.

Feasibility of using an isolated intestinal segment as an artificial organ for enzyme replacement therapy

Guinea pigs fed an ascorbic acid-deficient diet develop scurvy because of the absence of the enzyme L-gulonolactone oxidase. In theory if this enzyme is provided and its substrate L-gulonolactone is present at adequate concentrations ascorbic acid will be synthesized and the development of scurvy prevented. Using this model we tested whether a viable segment of intestine could be used to contain the administered enzyme and act as an artificial organ for the production of ascorbic acid. A surgical procedure was developed to prepare an externalized pouch of intestine with its circulation left intact. When enzyme is inserted in this intestinal bag it is not toxic and not antigenic in some animals, whereas, enzyme injected intraperitoneally is clearly antigenic. Synthesis of ascorbic acid by this artificial organ could not, however, be detected by elevation of plasma concentrations of the vitamin.