Hypoglycaemic effect of liposome-entrapped insulin administered intragastrically into rats.

The possibility of using liposomes as intragastric carriers of insulin was investigated in normal and diabetic rats. 1-3 units of insulin entrapped in dipalmitoylphosphatidylcholine cholesterol liposomes administered to normal rats decreased blood-glucose levels in 4 h to about 77% of those before treatment. Higher doses (4-2 and 8-4 units) extended this effect over 24 h. 1-0 units of insulin entrapped in the same liposomes had an even more pronounced effect in diabetic rats--levels of blood-glucose were reduced to 57% of pretreatment values after 4 h. Insulin entrapped in egg phosphatidylcholine/cholesterol liposomes was less effective. The effectiveness of liposome-entrapped insulin was similar in diabetic rats whether administered intragastrically or intraperitoneally but free insulin was more effective intraperitoneally. Radioimmunoassay of insulin in the serum confirmed that lowering of blood-glucose after the intragastric administration of liposome-entrapped insulin was related to the entry of at least some of the insulin into the circulation.