Figure 5.

Insulin potentiates agonist-induced increases in intracellular calcium in rat tracheal smooth muscle cells. Insulin (10 μM) did not cause an immediate, acute increase in intracellular calcium in cells preloaded with the calcium-sensitive indicator Fluo4 (A). However, pretreatment with 1 μM insulin for 3 h significantly increased baseline fluorescence (B). Methacholine (10, 1,000 μM, MCh) and serotonin (0.01–10 μM) each caused concentration-dependent increases in intracellular calcium (C and D, respectively, open circles), that were significantly potentiated in cells pretreated with 1 μM insulin for 3 h (C and D, filled circles). (n = 5). *P < 0.05.