Nutrient and pharmacological stimulation of insulin-secreting cells: marked differences in the onset of electrical...

Whole-cell current clamp experiments with the patch-clamp technique have been used to investigate the electrical activity of insulin-secreting (RINm5F) cells. When challenged with either glucose (10 mM), glyceraldehyde (10 mM), L-alanine (5 mM) or tolbutamide (100 microM) the cells depolarized and this led to the generation of spike potentials. Marked differences in the lag times between stimulation and the onset of electrical activity were observed. Both tolbutamide and L-alanine evoked spike potentials within on average 7 s of stimulation, whilst the effects of glucose and glyceraldehyde were only observed over a much longer delay. These variations may be explained by differences in the routes through which closure of ATP-sensitive K+ channels is brought about.