Volume 115, Issue 3, Pages 714-721 (September 1998) β-adrenergic regulation of ion transport in pancreatic ducts: Patch-clamp study of isolated rat pancreatic ducts  Ivana Novak  Gastroenterology  Volume 115, Issue 3, Pages 714-721 (September 1998) DOI: 10.1016/S0016-5085(98)70151-9 Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 1 Effect of adrenaline (10−6 mol/L) on the membrane voltage and conductance of a pancreatic duct cell in the nystatin whole-cell patch-clamp recording. The bottom trace of this original recording taken from the pen recorder shows the membrane voltage, Vm, made in a current-clamp mode, when the whole-cell current was clamped to zero during most of the experiment. The upper trace shows the whole-cell current, I. Periodically, for example during the adrenaline stimulation and immediately before and after stimulation, the cell voltage was clamped in several consecutive 10-mV steps below and above the cell potential, and the resulting current response is shown as steps in the upper trace. (The pulse steps were lasting 500 milliseconds, and only the plateaus are visible in the traces.) The whole-cell conductance was estimated from the current responses to given voltage steps, which can be presented as I/V plots as that shown in Figure 7. Gastroenterology 1998 115, 714-721DOI: (10.1016/S0016-5085(98)70151-9) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 2 Effect of different concentrations of phenylephrine on the membrane voltage (bottom trace) and the whole-cell current (top trace) of a single pancreatic duct cell. The voltage trace is interrupted by fast voltage-clamp protocols similar to that in Figure 1. Note small changes in Vm and whole-cell currents during stimulation. Gastroenterology 1998 115, 714-721DOI: (10.1016/S0016-5085(98)70151-9) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 3 Phenylephrine (10−6 mol/L) reversibly depolarizes Vm of pancreatic duct cells (P < 0.005). C, control period; Phenyl, period of stimulation with phenylephrine. Each curve represents recording from a single cell. Gastroenterology 1998 115, 714-721DOI: (10.1016/S0016-5085(98)70151-9) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 4 Effect of carbachol (CCH, 10−5 mol/L), phenylephrine (Phe, 10−6 mol/L), isoproterenol (Iso, 10−6 mol/L), ATP (ATP, 10−4 mol/L), and UTP (UTP, 10−4 mol/L) on [Ca2+]i as measured by changes in fura-2 fluorescence ratio 340/380 nm. Purinergic and cholinergic agonists increase [Ca2+]i by 300–400 nmol/L. Original traces A and B are examples of recordings from two different pancreatic ducts. Gastroenterology 1998 115, 714-721DOI: (10.1016/S0016-5085(98)70151-9) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 5 Effect of isoproterenol (β-agonist), propranolol (β-antagonist), and phentolamine (α-antagonist) on the Vm (lower trace) and the whole-cell current (upper trace) of a pancreatic duct cell in a nystatin whole-cell recording. The drugs were applied at the following concentrations: 10−8, 10−6, and 10−6 mol/L, respectively. Note that isoproterenol depolarizes Vm and increases whole-cell currents. For details of clamp protocols see the legend to Figure 1. Gastroenterology 1998 115, 714-721DOI: (10.1016/S0016-5085(98)70151-9) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 6 (A) Effect of isoproterenol (10−6 mol/L) on the Vm of 17 experiments and (B) on the cell membrane conductance, Gm, in 6 of these 17 experiments. Asterisks indicate that the test values for the agonist are significantly different from the control (*P < 0.05; **P < 0.005). C, control period; Iso, stimulation with isoproterenol. Gastroenterology 1998 115, 714-721DOI: (10.1016/S0016-5085(98)70151-9) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 7 Effect of isoproterenol (10−8 mol/L) on the whole-cell current/voltage relation of a pancreatic duct cell. Such curves are obtained from voltage-clamp protocols as shown in Figure 5. The increase in the slope of the curve with the agonist indicates an increase in Gm, and shift in Vm at zero current shows the depolarization. Gastroenterology 1998 115, 714-721DOI: (10.1016/S0016-5085(98)70151-9) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 8 Effect of low Cl− concentrations (5 mmol/L) on the Vm (lower trace) and the whole-cell current (upper trace) of a pancreatic duct cell stimulated with isoproterenol (10−6 mol/L), as indicated by the bars. For details of clamp protocols, see Figure 1. Gastroenterology 1998 115, 714-721DOI: (10.1016/S0016-5085(98)70151-9) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 9 Isoproterenol increases the Cl− conductance of pancreatic duct cells. □, Depolarizing effect of low Cl− concentrations (5 mmol/L) on the Vm of unstimulated duct cells; ▩, effect in duct cells stimulated with isoproterenol (10−6 mol/L). Asterisks indicate that the low Cl− solutions caused significant depolarization of Vm compared with Vm values obtained with solutions containing control Cl− concentrations (*P < 0.05; **P < 0.005). Gastroenterology 1998 115, 714-721DOI: (10.1016/S0016-5085(98)70151-9) Copyright © 1998 American Gastroenterological Association Terms and Conditions

Fig. 10 Concentration-response curves for isoproterenol and phenylephrine. The response is given as the change in Vm above the unstimulated value (Δ Vm). Numbers in parentheses indicate the number of experiments. Gastroenterology 1998 115, 714-721DOI: (10.1016/S0016-5085(98)70151-9) Copyright © 1998 American Gastroenterological Association Terms and Conditions