Figure 7.

Role of cAMP and PKA in the stretch response. (A) Intracellular levels of cAMP were measured in control cells (▪) and stretched cells (░⃞) after 15, 30, 120, or 300 min. Shown is mean ± SEM (n = 4). Values that are significantly different (p < 0.05) from matched control values are marked with an asterisk. (B) Effects of forskolin and H89 on capacitance. Cells were treated with 10 μM forskolin/500 μM IBMX without stretch (▪), treated with forskolin/IBMX and 10 μM H89 (▴), or stretched in the presence of 10 μM H89 alone (●). For comparison, the capacitance readings from Figure 1 of stretched (♦) and control (□) cells are shown. Shown is mean ± SEM (n = 6). (C) Effects of forskolin/IBMX on umbrella cell morphology. Tissue was treated with forskolin/IBMX without stretch for 5 h and processed for TEM. Notice the highly convoluted apical membrane. (D) Changes in surface area resulting from Forskolin/IBMX treatment. Tissue was treated with forskolin/IBMX (░⃞) and stereological analysis was performed as described. Control surface areas are shown for comparison (▪), n = 50. Values that are significantly different (p < 0.05) from matched control values are marked with an asterisk. (E) Endocytosis was determined in forskolin/IBMX-treated cells. Shown is representative Western blot after 0, 5, 15, 30, 60, or 120 min with or without MESNA treatment.