Specific glucose protection of pancreatic beta-cell function during culture in chemically defined medium

Microdissected pancreatic islets from non-inbred ob/ob-mice were cultured for 7 days in modified tissue culture medium 199 lacking serum. When 3 mM glucose was present during culture little or no insulin response to glucose stimulation was observed during the following incubation. Culture with 18 mM glucose on the other hand resulted in good preservation of glucose-stimulated insulin release, especially if release into the culture medium had been inhibited by lack of Ca++. High concentrations of leucine or its non-metabolizable analogue, 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid (BCH), stimulated insulin release into the culture medium but did not preserve glucose-stimulated insulin release. When compared to previously published fresh-islet levels, culture with 3 mM glucose alone or in combination with high concentrations of leucine or BCH resulted in a substantial loss of beta-cell insulin. This loss was less marked after culture with 18 mM glucose, and completely abolished if no Ca++ was included in the high glucose medium. The data indicate that glucose has a specific effect in protecting some glucoreceptor mechanism of the beta-cells during culture.