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PROCEEDINGS OF THE BIOCHEMICAL SOCIETY medium nor by the liver. The experiments with amyloglucosidase showed no difference in glycogen concentration in the liver nor in glucose release into the medium when compared with control perfusions. Nevertheless there was penetration of liver tissue by circulating amyloglucosidase during perfusion corresponding to 0.03-0.4mg of enzyme/g wet wt. of liver (corrected for endogenous glucosidase activity). The concentration in liver was never greater than that in the medium. When amyloglucosidase was administered intravenously to intact rats, a major proportion of the enzyme found in the liver was identified in a mitochondrial-lysosomal fraction prepared by the procedure of Lloyd (1969a), confirming the results of Lloyd (1969b). After perfusion with amyloglucosidase increased glucosidase activity was also associated with a mitochondrial-lysosomal fraction. Although penetration of liver lysosomes by amyloglucosidase apparently occurred during perfusion under the present conditions, the extent of this process was less than in vivo. This may be due to the absence of cofactors or to lysosomal damage in the isolated liver. Attempts to separate hepatocytes from Kupffer cells in an effort to identify the involvement of each in enzyme uptake in vivo have been made. We are grateful to the Wellcome Trust for financial support and to Professor Sir Ernst Chain for the use of departmental facilities.

[3H]Amyloglucosidase and 1311-labelled albumin were entrapped into liposomes (lipid spherules) composed of phosphatidyl choline, cholesterol and dicetyl phosphate (7 : 2 : 1 molar ratio). l3lI-labelled albumin was also entrapped in [3H]cholesterol-liposomes.Investigations on the fate in vivo following intravenous injection of such protein-containing liposomes into rats, showed that the bulk of liposomal radioactivity is removed from the blood within minutes. There is no measurable leakage of entrapped 1311-labelled albumin while liposomes are in the circulation.Most of the removed liposomal radioactivity was recovered in the liver. Autoradiographic examination of the liver 3 min after injection of albumin-containing [3H]cholesterol-liposomes suggests that hepatocytes and probably Kupffer cells are involved in the uptake of liposomes. It appears that liposomes enter this tissue intact but subsequently liposomal membranes and entrapped protein are catabolized.These catabolic processes are probably occurring in the liver lysosomes, as most of the liposoma1 radioactivity in this tissue was recovered in the mitochondrial-lysosomal fraction. Liposomes appear to be promising as a vehicle for the administration of enzymes and possibly also drugs to patients with storage diseases.In previous work [l] we reported the entrapment of albumin and Aspergillus niger amyloglucosidase into liposomes. Liposomes are lipid spherules formed when phospholipids are allowed to swell in aqueous media and become hydrated crystals [2,3].

The oral glucose tolerance test, a diagnostic procedure used in the detection of human diabetes, was used to study carbohydrate metabolism in rainbow trout, Sulmo guirdneri (Richardson). Fish exhibited pronounced and persistent hyperglycaemia on oral glucose administration. Hyperglycaemia was accompanied by decrease in blood amino acids, serum free fatty acids and cholesterol and marked increase in hepatic storage of glycogen. The incidence of oral glucose intolerance results, at least in part from insufficient circulating insulin. Exogenous insulin exerts a hypoglycaemic action and effectively abolishes the hyperglycacmia resulting from glucose administration. Tolbutamidc, the sulphonylurea hypoglycaemic drug, is without effect. Possibly as an indirect result of hyperadrenocorticism, oral glucose tolerance is markedly improved in the pre-spawning female. Longterm feeding of high carbohydrate diet to goldfish Cnrussiirs aurutus (L.) resultcd in gross hepatomegaly due to excessive hepatic glycogen accumulation and, possibly, fatty change of the liver. Protein metabolism was impaired as evidenced by protein depletion. Such degenerative changes in liver metabolism are probably a direct result of oral glucose intolerance and reflcct a metabolism adapted to diets normally low in available carbohydrate.

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