STUDY OF ANTIDIABETIC ACTIVITY OF WHITE SKINNED SWEET-POTATO (IPOMOEA-BATATAS L.) - COMPARISON OF NORMAL AND STREPTOZOTOCIN-INDUCED DIABETIC RATS AND HEREDITARY DIABETIC MICE

White skinned sweet potato (Ipomoea batatas L.) cortex (WSSP-cortex) w as found to have potential hypoglycemic activity in streptozotosin (ST Z) induced diabetic rats and hereditary diabetic mice (Type II, KK-A(Y )/Ta Jcl, C57BL/KsJ db/db) by oral administration. However, in normal rats, serum glucose levels were not changed by WSSP-cortex treatment. In glucose tolerance tests, treatment of normal and STZ diabetic rats by WSSP-cortex showed increased glucose tolerance and increased serum insulin levels like the tolbutamide treatment, whereas the treatment o f KK-AY and db/db mice showed increased glucose tolerance and decrease d serum insulin levels different from the tolbutamide treatment in res ponse to oral glucose load. These results suggest that the WSSP-cortex has quite unique properties such as the increase of insulin secretion and improving insulin resistance.