Effects of millimolar concentrations of glutaraldehyde on the electrical properties of frog skin.

Abstract

1. The effects of millimolar concentrations of glutaraldehyde on the electrophysiological properties of the epithelium of frog skin (Rana temporaria) were investigated. We recorded short-circuit current (Isc), transepithelial conductance (Gt) and impedance (Zt), fractional resistance (fRo) and the potential difference across the apical membrane (Vo). We used either Na+ or K+ as major mucosal cations to compare the effects on transepithelial Na+ and K+ currents (INa and IK) and thus on the apical Na+ and K+ permeabilities. 2. At concentrations above 0.005% (w/v) or 0.5 mM, glutaraldehyde irreversibly and completely inhibits both INa and IK within 2-3 h. The initial time courses of the inhibition of transepithelial currents following serosal and mucosal applications of the compound markedly differ. 3. Glutaraldehyde decreased Gt in sulphate Ringer solutions while it augmented Gt severalfold in chloride Ringer solution. 4. Measurements of the transepithelial impedance of tissues incubated with sulphate solutions showed that glutaraldehyde increased the resistances of both apical and basolateral membranes significantly. The capacitance of the apical membrane was augmented, while the basolateral membrane capacitance was drastically decreased. 5. Microelectrode impalements of the granulosum cells showed that glutaraldehyde decreased Vo by more than 40 mV and increased fRo, which reached values around 90%. 6. The role of free amino groups in ion-transporting proteins and the potential non-fixative uses of protein cross-linkers in epithelia are discussed.

Effect of insulin on area and Na+ channel density of apical membrane of cultured toad kidney cells.

“…they were not generated by a system dominated by a single time constant. Indeed, as shown in the figure they were fitted successfully by a model that includes two RC networks in series (Margineanu & Van Driessche, 1990 Table 3. The average value for the high frequency component was 1P48 ,sF cm-2 while the capacitance associated with the low frequency time constant was 12-6 ,uF cm2.…”

“…Therefore, the sum of eqns (1) and (2) was fitted to the power density spectra to determine the Lorentzian parameters (S. and f0) by nonlinear curve fitting (Van Driessche & Erlij, 1983). In the present study we recorded the blocker-induced noise using five (Margineanu & Van Driessche, 1990). The mean value of the transepithelial potential remained clamped at 0 mV.…”

“…5 curves b and c). These data were then fitted with the equation for a second-order system which describes the behaviour of the two-membrane model (Margineanu & Van Driessche, 1990):…”

“…The relations between A, B, C and D and the resistance and capacitance of the apical and basolateral membrane were derived by Margineanu & Van Driessche (1990). The apical equivalent resistance (Ra) and capacitance (Ca) and its basolateral equivalents (Rb and 0b) were determined as previously described (Margineanu & Van Driessche, 1990). …”

Electrogenic bicarbonate secretion by prairie dog gallbladder

“…Because the leaky nature of the gallbladder required a wide range of frequencies to calculate impedance, we focused this report on estimates of the R a and Rb, given the potential for capacitance to be frequency-dependent when R a Х Rp Rb (36,37). Unlike capacitance, individual membrane resistance is calculated from the real term of impedance (Z R) and is frequency-independent (1,23,29) given the relationship Z (j) ϭ V /I, which simplifies to Z R ϭ R (23).…”