Acute stimulatory effect of tumor necrosis factor on the basolateral 50 pS K channels in the thick ascending limb of the rat kidney.

ABSTRACT

The aim of the present study was to investigate the acute effect and mechanism of tumor necrosis factor (TNF) on basolateral 50 pS K channels in the thick ascending limb (TAL) of the rat kidney. The TAL tubules were isolated from the rat kidney, and the activity of the 50 pS K channels was recorded using the patch­clamp technique. The results indicated that the application of TNF (10 nM) significantly activated the 50 pS K channels and the TNF effect was concentration­dependent. Inhibition of protein kinase A, phospholipase A2 and protein tyrosine kinase using pathway inhibitors (H89, AACOCF3 and Herbimycin A, respectively) did not abolish the stimulatory effect of TNF, indicating that none of these pathways mediated the TNF effect. By contrast, the phenylarsine oxide inhibitor against protein tyrosine phosphatase (PTP) decreased the activity of the 50 pS K channels and blocked the stimulatory effect of TNF on these channels. Furthermore, western blot analysis demonstrated that the application of TNF (10 nM) in the TAL increased the phosphorylation of PTP, an indication of PTP activity stimulation. Thus, it was concluded that the acute application of TNF may stimulate the basolateral 50 pS K channel in the TAL and the stimulatory effect of TNF may be mediated by the PTP­dependent pathway.