The aim of this project is to combine biophysical, biochemical
and morphological approaches to investigate the mechanisms which couple stimuli to insulin release in both normal pancreatic islets and in islets from animals with biabetes-like syndromes. Glucose-induced insulin release is modulated by several hormones and neurotransmitters. It has been hypothesized that these agents regulate insulin secretion, at least in part, by interacting with plasma membrane K- or Ca-channels. 1) This possibility will be investigated by simultaneous measurement intracellular Ca 2+ concentration (!Ca2+!i) and either membrane potential or ion channel activity. 2) The role of second messenger systems (G-proteins, protein kinase C and adenylate cyclase) will be evaluated using biophysical and biochemical methods. The perforated patch-clamp configuration will be used to study whole-cell current modulation. The role of G-proteins in all these processes will be investigated using activators (GTP analogues, AlF-4) and inhibitors (pertussis toxin) of G-proteins, purified G-protein subunits and specific antibodies against these subunits. 3) Despite the functional heterogeneity the islet behaves as a "syncithium". Intercellular coupling through gap junctions may also bring about signal
synchronization so that less responsive cells may be induced to secrete by active neighbouring cells. In this regard: a) the relationship between the electrical properties of the B-cell and the functional heterogeneity of B-cells in terms of insulin
secretion and biosynthesis will also be determined, and b) it will be also studied the regulation of the gap junctions (which are likely to form the structural basis for the islet to perform a synchronized response to nutrients and secretagogues).
Funding SchemeCSC - Cost-sharing contracts
OX1 3PT Oxford