ONKEN, H*; MOFFETT, SB; MOFFETT, DF; Washington State University, Pullman; Washington State University, Pullman; Washington State University, Pullman: The transepithelial voltage of the isolated anterior stomach of mosquito larvae (Aedes aegypti): Characterization of the serotonin-stimulated cells.

The lumen-negative transepithelial voltage (V_te) of the isolated and perfused anterior stomach of mosquito larvae (Aedes aegypti) was studied with a �semi-open� preparation in which one end of the gut was ligated onto a perfusion pipette and the other end remained open to the bath. All experiments were performed with serotonin-stimulated preparations displaying voltages between -9 and -65 mV. V_te was abolished after addition of 2.5 mmol l^-1 dinitrophenol and depended on the presence of Cl^–. Na⁺ substitution experiments showed that a major part of V_te depended on the presence of this cation in the hemolymph-side bath. Addition of 10 μmol l^-1 concanamycin (78 � 6 % inhibition) or 2.5 mmol l^-1 ouabain (15 � 2 % inhibition) to the bath partially inhibited V_te. DPC (0.5 mmol l^-1) or DIDS (0.1 mmol l^-1) partly inhibited V_te when applied to the hemolymph-side bath. When present on both sides of the epithelium, these inhibitors caused further V_te reductions. Hemolymph-side furosemide (0.1 mmol l^-1) or BaCl₂ (5 mmol l^-1) partly inhibited V_te. When applied to the hemolymph-side, amiloride (0.2 mmol l^-1) significantly decreased V_te, whereas the drug caused no further effect when it was subsequently also applied to the luminal side of the epithelium. The above results are the basis for an extended model for the cellular mechanisms of NaHCO₃ secretion / HCl absorption involved in alkalization of the anterior stomach of mosquito larvae. Financial support by NSF (IBN-0091208) is gratefully acknowledged.