POSSIBLE MODULATORY ROLE OF NONACTIVATED LYMPHOCYTES ON INSULIN-SECRETION

In order to study the probable physiological role of non-activated lym phocytes on islet B-cells, we incubated and perfused rat pancreatic is lets in the presence of low (2.8 mM) and high (16.7 mM) glucose concen trations after pre-exposure for 60 min to rat lymphocytes or to substa nces secreted by lymphocytes. Insulin secretion and Rb-86(+), Ca-45(2) and [H-3]-phosphoinositide metabolite fluxes were lower compared to controls when islets were pre-exposed to lymphocytes but were not diff erent when islets were pre-exposed to substances secreted by lymphocyt es. These alterations in isotope flux suggest that, when lymphocytes a nd islets are in contact, closure of potassium channels and a paradoxi cal effect of glucose load on insulin release occur in the presence of low glucose concentrations. The alterations observed are probably due to a swift and direct action of lymphocyte secretion perhaps induced by a direct contact of islet cells.