Involvement of IRS-1 in L-783,281–stimulated increases in [Ca2+]i and exocytosis. Involvement of IRS-1 in L-783,281–stimulated increases in [Ca2+]i and exocytosis. A: Representative Ca2+ trace of a fura-2 loaded IRS-1–/– β-cell stimulated with 18 mmol/l glucose and the same cell stimulated with 10 μmol/l L-783,281. The horizontal bar under the trace indicates time of stimulation. B: Amperometric trace of a single IRS-1+/+ β-cell stimulated with 10 μmol/l L-783,281 (top), a IRS-1–/– β-cell stimulated with 10 μmol/l L-783,281 (middle), and the same IRS-1–/– β-cell stimulated with 18 mmol/l glucose (bottom). Michael G. Roper et al. Diabetes 2002;51:S43-S49 ©2002 by American Diabetes Association