The proposed research will determine which opiate peptides are abundant in the pancreas of normal rats and which peptides are altered in content in the pancreas of hypoinsulinemic and diabetic rodent models. The techniques to be used to characterize the opiate peptides include gel filtration chromatography, reverse phase high performance liquid chromatography, radioimmunoassay, and other techniques such as digestion by proteolytic enzymes. Localization of specific opiate peptides within the islets of Langerhans, rather than in the acinar pancreas, will be determined by both (a) extraction and chromatography of opiates from islets isolated by the collagenase method and (b) immunohistochemistry using opiate-directed first antibody and a peroxidase-antiperoxidase technique. The hypo-insulinemic models to be studied include the streptozotocin-diabetic rat, which has previously been shown to have drastically reduced total opiate content in the pancreas; alloxan-induced diabetes in the rat; the genetically diabetic rat (B/B), which has an autoimmune disease course; the mildly hypoinsulinemic, hypophysectomized rat as well as two genetically growth hormone-deficient models (dw/dw and lit/lit mice) and matched controls. In addition, the genetically diabetic db/db mouse (and its controls) will be studied longitudinally, during the early, hyperinsulinemic-hyperglycemic phase as well as the late, hypoinsulinemic phase. The effects of insulin replacement or pituitary hormone replacement on pancreatic opiate content will be studied, as appropriate. The long-term objective is to understand the role of endogenous opiate peptides in modulating insulin secretion in humans as well as rodents. In particular, a possible role for opiate peptides in the pathogenesis of non-insulin-dependent diabetes has been suggested and needs further investigation. The proposed initial studies of islet opiate content in rodents will combine biochemical and histological methods and will seek correlations with physiological variables in the animal models (such as rate of insulin secretion). In the future, the modulation of insulin secretion rates by specific opiate peptides will be studied more directly using the information gathered in the studies proposed here. It may eventually be possible to design a drug which will specifically correct opiate-mediated defects in glucose-stimulated insulin secretion and can be used to treat non-insulin-dependent diabetics.
| Timmers, K; Coleman, D L; Voyles, N R et al. (1990) Neuropeptide content in pancreas and pituitary of obese and diabetes mutant mice: strain and sex differences. Metabolism 39:378-83 |
| Timmers, K I; Palkovits, M; Coleman, D L (1990) Unique alterations of neuropeptide content in median eminence, amygdala, and dorsal vagal complex of 3- and 6-week-old diabetes mutant mice. Metabolism 39:1158-66 |
| Powell, A M; Wells, M R; Timmers, K I et al. (1987) Autoradiographic localization of [3H]-guanidinoethylmercaptosuccinic acid binding sites in rat islets of Langerhans. Life Sci 40:2511-3 |
