SENSITIVITY OF VALINOMYCIN-BASED K-SELECTIVE MICROELECTRODES TO INHIBITORS OF K+ TRANSPORT()

The sensitivies of double-barrelled K+-selective micro-electrodes (KSM s) employing the low-impedance membrane cocktail based on the neutral K+-selective ion carrier valinomycin (Fluka, Cocktail B 60398) to the following 3 different classes of inhibitors of K+ transport were measu red: (1) general metabolic inhibitors (dinitrophenol, potassium cyanid e, sodium azide, rotenone, dicyclohexylcarbodiimide, salicylhydroxamic acid); (2) P-type ATPase inhibitors (vanadate, ouabain, amiloride, SC H 28080); and (3) anion-dependent K+ transport inhibitors (bumetanide, 4-acetamide-4-isothiocyanostilbene-2,2-disulphonic acid). Of the 12 i nhibitors tested, only dinitrophenol had any significant effect on the response of KSMs to K+ activity. Comparison of the calibrations in so lutions with and without 0.1 mM dinitrophenol showed that this inhibit or behaved as a 'classical' interferent whereby its contribution to th e K+ activity signal was statistically significant at K+ activities of 36.0 mM and less. However, at higher K+ activities (97.0 mM), dinitro phenol interference was not significant. It was possible to correct fo r the DNP interference and to obtain measurements of intracellular Kactivity in insect muscles.