Identification of two strains of cultured canine renal epithelial cells (MDCK cells) which display entirely different physiological properties.

Cultured monolayers of Madin-Derby canine kidney (MDCK) cells grown upon permeable filter supports display many features of in vivo epithelia. Measurements of transmonolayer resistance, open-circuit p.d., dilution and bi-ionic p.d.s have been made of MDCK monolayers mounted in Ussing-type chamber (0.75 cm window radius). Previously reported values of transmonolayer resistance of 100 omega cm2 (Cereijido, Robbins, Dolan, Rotunno & Sabatini, 1978; Misfeldt, Hamamoto & Pitelka, 1976) indicate a 'leaky' epithelium. The major finding of this work is that MDCK monolayers can also display values of transmonolayer resistance similar to 'tight' epithelia (mean value = 4116 omega cm2). The reason for such differences is the existence of separate strains of MDCK cells. High-resistance monolayers originate from cell stocks of sixty serial passages whilst low-resistance monolayers originate from cell stocks of 109 serial passages. Measurements of transmonolayer dilution, and bi-ionic p.d.s together with Na ion tracer fluxes and electron microscope observations of La3+ penetration through the apical tight junctions, substantiate the finding of high-resistance properties in MDCK monolayers and confirm the existence of two separate MDCK cell strains displaying entirely different physiological properties. Differences extend to cellular morphology and cellular volume in the two strains of MDCK cells.