The potential and short-circuit current across isolated rumen epithelium of the sheep

Abstract

A technique is described for working with isolated sheets of rumen epithelium. Epithelium was obtained at operations for rumen fistula-tion or in acute experiments and was rapidly mounted between two cone-shaped chambers each of which held 40 ml. of bathing fluid. The fluids were gassed with 95% O2/5%CO2 and 20 cm2 of epithelium was exposed to the fluids. Electrical measurements were made of (a) the potential generated across the epithelium, (b) the short-circuit current which flowed and (c) the resistance of the epithelium. The results are grouped according to the composition of the sheep Ringer solution used to bathe the epithelium. The most stable preparation was obtained when the solutions contained 5m[image] each of glucose, acetate, propionate and butyrate as well as bicarbonate and phosphate buffers. In Cl- media, the average initial p.d., short-circuit current (s.-c.c.) and resistance were 9-3 mV, 11.''6 [mu]A/cm2 and 1156 [OMEGA]. cm2 respectively. Higher values of 17.6mV, 17.3[mu]A/cm2 and 1501 [OMEGA].cm2 were recorded in SO42- media. In both media, the s.-c.c. declined at approximately 1.5[mu]A/cm2.hr. and preparations were suitable for study over periods from 4 to 6 hr. When the concentration of K was varied on either side of the epithelium at constant [Na+], the potential showed a linear relation with log [K+] for both sides of the epithelium. Changing the Na concentrations at constant [K+] on either side of the epithelium caused negligible alterations in the potential. Exclusion of Na from the media bathing both sides of the epithelium abolished the potential and s.-c.c. The addition of ouabain to the blood side of the preparation abolished the potential and s.-c.c. whereas on the rumen side these parameters were unaffected.