MACROAGGREGATED ALBUMIN POTENTIATES THE HYPOGLYCEMIC EFFECT OF MICROENCAPSULATED ISLETS IN THE FED STATE OF STREPTOZOTOCIN-INDUCED DIABETICMICE

Prolonged postprandial hyperglycaemia was noted in streptozotocin-indu ced diabetic mice which had been treated intraperitoneally with 2000-3 000 alginate-poly-1-lysine-alginate (A-P-A) microencapsulated rat isle ts. We hypothesized that the persistent postprandial hyperglycaemia wa s due to shortage of intracapsular calcium ion. In order to study the effect of encapsulated macroaggregated albumin (MAA) on the function o f microencapsulated islets, we coencapsulated MAA and islets in A-P-A microcapsules which we implanted intraperitoneally into streptozotocin -induced diabetic mice. From binding study and Scatchard analysis, we found that MAA-containing A-P-A microcapsules had a lower calcium bind ing affinity 5.24 +/- 1.20 mM versus 2.35 +/- 0.86 mM, n = 12, p < 0.0 1) and a higher calcium binding capacity (14.34 +/- 1.22 mu g/mg versu s 7.24 +/- 0.82 mu g/mg, n = 12, p < 0.01) than empty A-P-A microcapsu les. After intraperitoneal transplantation of 2000-3000 microcapsules containing islets and encapsulated MAA, the basal and postprandial blo od glucose levels of the treated diabetic mice were not significantly different from that of normal mice. The improvement of persistent post prandial hyperglycaemia in these treated diabetic mice was not due to the difference of food intake in amount. In conclusion, A-P-A microcap sules containing islets and encapsulated MAA functioned better than mi crocapsules containing islets alone in treating streptozotocin-induced diabetic mice. The former preparation restored both fasting and postp randial hyperglycaemia and put these treated diabetic mice into a cure d status of diabetes.