FIGURE 10.
Isoproterenol enhances carbachol-promoted increases in QO2 and [Ca2+]i in rat parotid acinar cells. A, shown are increases (ΔQO2) in the rate of O2 consumption of parotid cells exposed to 10−5 m carbachol in cells pretreated (or not) with 10−7 m and 10−5 m isoproterenol (Iso) for 2 min before carbachol. The rates in the presence of isoproterenol were normalized to the control ΔQO2 value (18.9 ± 0.4 nmol of O2/mg of protein/min, n = 3) in the presence of carbachol alone (−). n = 3. *, p < 0.05. B, increases in intracellular Ca2+ in cells suspended in Ca2+-containing Solution A and stimulated with 10−6 and 10−5 m carbachol (CCh) in the presence (+Iso) or absence (−Iso) of 10−5 m isoproterenol. Shown are individual traces from one experiment. The ordinate axis is the 340/380-nm Fura-2 fluorescence excitation ratio. C, cumulative data show the stimulatory effects of isoproterenol (10−5 m) and forskolin (10−5 m) on the initial peak Ca2+ increase produced by carbachol (10−6 m, 10−5 m), as shown in B. Data were normalized to the increases in the Fura-2 ratio produced by carbachol alone (10−6 m, 1.06 ± 0.12, n = 3; 10−5 m, 2.34 ± 0.13, n = 8). Numbers at the bottom of the bars indicate number of experiments. *, p < 0.01 versus control. D, shown is the stimulatory effect of isoproterenol (10−5 m) on intracellular Ca2+ release promoted by 10−5 m carbachol in Fura-2-loaded cells suspended in Ca2+-free Solution A and the entry of Ca2+ when CaCl2 (1 mm) was added to cells after depletion of Ca2+ stores. Shown are individual traces from one experiment. The ordinate axis is the 340/380-nm Fura-2 fluorescence excitation ratio. E, cumulative data show the stimulatory effects of isoproterenol (10−5 m) on the peak Ca2+ increase due to carbachol-promoted Ca2+ release and the subsequent Ca2+ peak due to Ca2+ entry as shown in D. Increases in the Fura-2 ratio from isoproterenol-treated cells were normalized to the increases produced in the absence of isoproterenol (10−6 m, release, 0.74 ± 0.05, n = 4; entry, 1.32 ± 0.21, n = 4; 10−5 m, release, 1.28 ± 0.10, n = 8; entry, 2.05 ± 0.13, n = 9). *, p < 0.01 versus control; #, p < 0.05 versus control. F, cumulative data show the effect of treatment of cells with H-89 (2 μm, 10 min) before initiating the stimulatory effect of isoproterenol on the carbachol (10−5 m)-promoted Ca2+ release and uptake as shown in D. *, p < 0.05. n = 4.