CYTOKINES AFFECT ION-TRANSPORT IN PRIMARY CULTURED THICK ASCENDING LIMB OF HENLES LOOP CELLS

Tumor necrosis factor-alpha (TNF) and interleukin-1 (IL-1) affect epithelial cell ion transport. However, the site of action along the nephron has not been elucidated fully for these cytokines. Thus, the effect of TNF and IL-1 on the ion transport function of primary cultured medullary thick ascending limb of Henle's loop (mTALH) cells was determined by measuring rubidium (Rb-86) uptake. TNF, IL-1, and lipopolysaccharide (LPS), a known activator of cytokine production, inhibited Rb-86 uptake by cultured mTALH cells after a 24-h incubation period but had no effect when incubated with the cells for 1 or 4 h. Furthermore, mTALH cells produced biologically active TNF after stimulation with LPS for 24 h, and the LPS-induced inhibition of Rb-86 uptake was abolished in the presence of an anti-TNF antibody, suggesting that TNF produced by the mTALH cells acted in an autocrine manner to inhibit Rb-86 uptake. The effects of LPS on Rb-86 uptake also were inhibited by the cyclooxygenase inhibitor, indomethacin. As TNF increased prostaglandin E(2) synthesis by cultured mTALH cells and as prostaglandin E(2) also inhibited Rb-86 uptake, LPS presumably inhibited Rb-86 uptake by inducing a TNF-mediated increase in prostaglandin synthesis. These data demonstrate that a prostanoid produced by mTALH cells mediates the inhibitory effect of LPS and TNF on Rb-86 uptake and imply that endogenous TNF inhibits ion fluxes in the mTALH via a prostaglandin-dependent mechanism.