Cells in culture from rabbit medullary thick ascending limb of Henle's loop.

Freshly isolated cells obtained from the medullary segment of the rabbit thick ascending limb of Henle's loop (mTALH) metabolize arachidonic acid (AA) primarily by the cytochrome P-450 monooxygenase pathway forming several products; a vasorelaxant and an inhibitor of Na+-K+-ATPase have been identified. These studies have been extended to mTALH cells in culture. The ability of cells isolated from 1-mo-old rabbits to grow in culture far surpassed that of cells isolated from adult rabbits, whereas similar cytochrome P-450-dependent AA metabolites were produced by freshly isolated cells from rabbits of both ages. Three-week-old mTALH cultures formed ouabain-sensitive "domes" when grown on plastic surfaces and developed transepithelial voltages (4.7 + 1.2 mV, n = 6) when grown on gas-permeable surfaces. Electron microscopy of the cells showed typical mTALH cell characteristics. The presence of Tamm-Horsfall protein, a surface membrane protein of mTALH cells, in 90-95% of the cells confirmed the homogeneity of the cultures. Although several environmental manipulations were tested, mTALH cells in culture did not produce the same cytochrome P-450-dependent AA metabolites as those produced by mTALH cells before culture. However, a cytochrome P-450-dependent AA metabolite that differs from the AA metabolites formed by freshly isolated mTALH cells was produced by hemin-treated mTALH and heterogenous cell cultures.