Figure 5. Effect of G protein stimulation with GTP-γS. (a) Original current recording showing the effect of 1 μM epinephrine on the conductance of an oocyte expressing the β-adrenergic receptor and CFTR. The holding potential was alternating between −40 and −60 mV with a 1 Hz frequency. (b) The same protocol was applied to an oocyte injected 13 min before with 50 nl of a 1.8-mM GTP-γS solution. (c) Effect of trypsin (2 μg/ml for 3.5 min) on the amiloride-sensitive Na+ current (INa) at −100 mV after intracellular injection with GTP-γS (50 nl, 1.8 mM). (d) The effect of a 3-min trypsin treatment (left) on INa (before trypsin, white bars; after trypsin, black bars) in oocytes expressing αβγXENaC. Nine oocytes were injected with GTP-γS, and seven control oocytes were noninjected. The effect of trypsin was not affected by previous GTP-γS intracellular injection. (right) The whole oocyte conductance in oocytes expressing CFTR and the β2-adrenergic receptor before (open bars) and after (filled bars) stimulation with 1 μM epinephrine. In control oocytes (n = 11) (i.e., without previous GTP-γS injection), epinephrine induced an increase of the whole oocyte conductance (P < 0.005, paired t test). Intracellular GTP-γS injection (n = 13) increased the oocyte conductance (P < 0.05, unpaired t test) and completely prevented the effect of epinephrine.
Image published in: Chraïbi A et al. (1998)
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