from experiments using Fura-2-loaded canine airway smooth muscle cells grown to confluence then serum deprived in insulin-supplemented medium for 7 days. Each tracing is the mean of 8-12 elongate cells identified in a single microscopic field. Cells were first stimulated with methacholine (MCh1, left panels) (10 -9 to 10 -5 M) and changes in intracellular Ca 2+ ([Ca 2+ ] i ) recorded. Thereafter, cells were incubated with either vehicle (top row) or latrunculin-A (1M, 37°C) (bottom row) for 1 hour, and were subsequently treated with methacholine (MCh2) at the same concentration used for MCh1. Changes in [Ca 2+ ] i in response to MCh2 were recorded for the same cells monitored after MCh1 treatment. (B)Concentration-response curves for MCh2 in control and latrunculin-A-treated cells plotted as peak [Ca 2+ ] i . Curves are derived using individual **data** points that are the mean ± s.e.m. of at least 30 cells in total (assayed in at least three different experiments). *P<0.05, **P<0.01, for control versus latrunculin A at a given MCh concentration. cells (Fig. 4D,E). These **data** indicate that -dystroglycan is essential for the association of caveolin-1 with lipid rafts and for supporting caveolae formation and/or stability.