ABSTRACT
Effects of intracellular Na+, K+ and Cl- on Ca(2+)-regulated exocytosis activated by 10 microM acetylcholine (ACh) were studied in guinea-pig antral mucous cells which are permeabilized by nystatin treatment. Ca(2+)-regulated exocytotic events were modulated by [Na+]i, [K+]i and [Cl-]i via mediation of PTX-sensitive G proteins. Increases in [Na+]i and PTX inhibit G protein (G(Na)), which suppressed the exocytosis. Increases in [K+]i caused the exchange of G proteins (from G(Na) to G(K)) to increase, and GK evoked activation of the exocytosis and was inhibited by PTX. Increases in [Cl-]i and PTX inhibit G protein (G(Cl)), which stimulates exocytotic events. Based on these observations, the exocytosis in antral mucous cells were modulated by intracellular ions, concentration of which were increased or decreased by cell volume changes caused by Ach.
Subject(s)
Acetylcholine/pharmacology , Animals , Cell Membrane Permeability/drug effects , Exocytosis/physiology , Exocytosis/drug effects , Gastric Mucosa/metabolism , Gastric Mucosa/cytology , Guinea Pigs , Hypertonic Solutions/pharmacology , Ionophores/pharmacology , Nystatin/pharmacology , Pertussis Toxin/pharmacology , Potassium/pharmacokinetics , Pyloric Antrum/metabolism , Pyloric Antrum/cytology , Sodium Chloride/pharmacokinetics , Vasodilator Agents/pharmacologyABSTRACT
Caryopses of two Triticum estivum genotypes, differing in salt tolerance [Sakha 8, tolerant, Giza 162, sensitive], were hydroponically grown under natural environmental conditions [in the laboratory] in presence and absence of different concentrations of NaCl added to the growth medium. NaCl stress increased nonelectrolyte permeability of leaf sheath subepidermal cells in Giza 162 [sensitive], whereas no such effect of salt was found in Sakha 8 [tolerant]. Psi s of leaf sheath subepidermal cells of both cultivars was decreased with rising NaCl concentration in the external solution. At 100 mM NaCl, the decrease in psi s in Giza 162 was greater than that found in Sakha 8. Cytoplasmic viscosity of Giza 162 was decreased by NaCl addition to the growth solution, although viscosity was higher in Giza 162 than in Sakha 8 under control condition [O mM NaCl]. Cytoplasmic viscosity in Sakha 8, however, did not change by salt stress. The results confirmed and extended earlier data that cytoplasmic characteristics are different in wheat salt sensitive and tolerant genotypes, they may correlate with salt tolerance