Electrophoretic method of ion injection in single kidney cells.

Electroplysiological studies of the electroclhemical profile across the r-enal epitheliuim lhave contributtecl to ouir uin(ler-standlino of the meclhanism responsible for soditlm reabsorption. In particillar stuclh sttudies have defined the electrical potential step across the lutminal and peritubular cell membrane aind lhave madle it possible to locate a meclhanism for active Na extrusion at the peritubiular cell boundary(l). Few teclhniqtues lhave been available to study transport pllIenomena at the single cell level. One way to obtain information at this level is to concluct stuLdies on tissue slices. Alterations of intracellular ion content and cell potential difference in kidney slices exposedl to a variety of soaking procedIures pelmit an analysis of ion fluxes across single cell membranes(2). Slice teclhniques, hlowever, lea(l to the dlisrtuption of the ttubLular geomnetry of the renal epitlhelitum and of the normal asymmetrical belhavior of kidney cells witlh respect to transport. Ideally, intracellular ion concentrations shotuld 1)e modlifie(l by means of a teclhniqtue maintaining the integrity of the tubular epitlhelium and allowinig fothe assessment of the sodium punmp at the single cellular level. To this end, we developed an intracelltliar electroplioretic ion injection teclhniqtue applicable to Nectltrlts proximal tuLbuile cells. Similar methods lhave been used extensively in excitable tissues(3). In the iM vivo or (loul)ly-perfuse(d ki(dniey of Nelctirlts, it is possilble to impale single proximal tutbuile cells by means of a (louible-barreled microelectrode as indicated in Fig. 1. The peritubular membrane potential difference can be recordled as well as its alteration after cation injection in the same cell. One barrel of the electro(le is filled witlh 3 Al KCI and meastures the potential difference between the cell interior and the surface of the kidney. The otlher barrel is used for cuLrrent injection and contains concentrated solutions of potassium acetate,