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Comparison of cellular and medium insulin and GABA content as markers for living -cells

Diabetes Research Center, Vrije Universiteit Brussel, Brussels, Belgium

Submitted 26 May 2004 ; accepted in final form 17 September 2004

Experimental and therapeutic use of islet cell preparations could benefit from assays that measure variations in the mass of living -cells. Because processes of cell death can be followed by depletion and/or discharge of cell-specific substances, we examined whether in vitro conditions of -cell death resulted in changes in tissue and medium content of insulin and of -aminobutyric acid (GABA), two -cell-specific compounds with different cellular localization and turnover. Exposure of rat purified -cells to streptozotocin (5 mM, 120 min) or to the nitric oxide donor GEA-3162 (GEA; 50 µM, 120 min) caused 80% necrosis within 24 h; at the end of this period, cellular insulin content was not significantly decreased, but cellular GABA content was reduced by 70%; when cultured at basal glucose (6 mM), the toxin-exposed cells did not discharge less insulin but released 80% less GABA in the period 8–24 h. As in rat -cell purification, GABA comigrated with insulin during human islet cell isolation. Twenty-four hours after GEA (500 µM, 120 min), human islet cell preparations exhibited 90% dead cells and a 45 and 90% reduction, respectively, in tissue insulin and GABA content; in the period 9–24 h, insulin discharge in the medium was not reduced, but GABA release was decreased by 90%. When rat -cells were cultured for 24 h with nontoxic interleukin (IL)-1 concentrations that suppressed glucose-induced insulin release, cellular GABA content was not decreased and GABA release increased by 90% in the period 8–24 h. These data indicate that a reduction in cellular and medium GABA levels is more sensitive than insulin as a marker for the presence of dead -cells in isolated preparations. Pancreatic GABA content also rapidly decreased after streptozotocin injection and remained unaffected by 12 h of hyperglycemia. At further variance with insulin, GABA release from living -cells depends little on its cellular content but increases with IL-1-induced alterations in -cell phenotype.

islet; diabetes; -cell death; -aminobutyric acid

This article has been cited by other articles:

				C. Wang, R. Mao, M. Van De Casteele, D. Pipeleers, and Z. Ling Glucagon-like peptide-1 stimulates GABA formation by pancreatic beta-cells at the level of glutamate decarboxylase Am J Physiol Endocrinol Metab, April 1, 2007; 292(4): E1201 - E1206. [Abstract] [Full Text] [PDF]

				C. Wang, K. Kerckhofs, M. Van de Casteele, I. Smolders, D. Pipeleers, and Z. Ling Glucose inhibits GABA release by pancreatic beta-cells through an increase in GABA shunt activity Am J Physiol Endocrinol Metab, March 1, 2006; 290(3): E494 - E499. [Abstract] [Full Text] [PDF]