Different time courses of GTP[gamma-S]-induced exocytosis and current oscillations in isolated mouse pancreatic acinar cells.
Exocytosis in isolated mouse pancreatic acinar cells was investigated using the dual-frequency method for measuring membrane capacitance and ionic conductances. Under control conditions, single exo- and endocytotic events could be resolved. The total cell capacitance slightly decreased to 98.7 +/- 0.9% of the initial cell capacitance within 10 min after establishing the whole-cell configuration. When guanosine 5'-O-(3-thiophosphate) (GTP[gamma-S] was added to the patch pipette, stepwise elevations in membrane capacitance occurred and the cell capacitance increased to 106.7 +/- 1.6% within 10 min. Exocytosis was also stimulated by GTP[gamma-S] when a Ca2+-free pipette solution supplemented with 1 to 10 mM ethylenebis(oxonitrilo) tetraacetate (EGTA) was used. Measurement of the DC current component in parallel with AC current analysis was used to isolate components of the Ca2+-dependent Cl- and monovalent cation conductances from the whole-cell conductance. These experiments demonstrate that in GTP[gamma-S]-stimulated pancreatic acinar cells: (1) activation of Cl- currents precedes that of cation currents, and (2) fusion of the zymogen granule membrane with the plasma membrane does not lead to incorporation of active Cl- or nonselective cation channels (>/= 10 pS).
Schmid
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2. Physiologisches Institut, Universität des Saarlandes, D-66421 Homburg/Saar, Germany.
Schulz
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D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D004072:Digitonin / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004553:Electric Conductivity; D005089:Exocytosis / Q000187:drug effects*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology*; D066298:In Vitro Techniques; D051379:Mice; D010179:Pancreas / Q000166:cytology* / Q000187:drug effects; D013997:Time Factors
D016244:Guanosine 5'-O-(3-Thiotriphosphate); D004533:Egtazic Acid; D002217:Carbachol; D004072:Digitonin