Tumor Necrosis Factor Enhanced The Effect Of Endothelin On Renal Vasoconstriction In Isolated Perfused Rat Kidney

AIMHepatorenal syndrome (MRS) with poor prognosis is a severe complication in advanced liver disease . Decreased renal perfiision caused by renal vasoconstriction is the key factor of pathogenesis. Recent study shows that tumor necrosis actor - a( TNF-a) enhances the expression of type I inositol 1,4,5 - triphos-phate receptors (IP3R) protein and I IP3R mRNA in cultured rat glomerular afferent arterioles smooth muscle cells. The aim of this work is to explore the effect of TNF-a on endothelin (ET) renal vasoconstriction by isolated perfused rat kidney.MATERIALS AND METHODSMale wistar rats weighing 260 - 320g were used and were divided into 6 groups randomly: 1. A group: ET' s stimulation after being perfused by kreb' s solution for 90 minutes;2. a group;no ET' s stimulation after being perfused by kreb' s solution for 90 minutes; 3. B group: ET' s stimulation after being perfused by kreb'.s solution with TNF-a( 1 u,g/L) for 90 minutes;4. b group: no ET' s stimulation after being perfused by kreb' s solution with TNF-a ( 1 jxg/L) for 90 minutes;5. C group ;ET' s stimulation after being perfused by kreb' s solution with heparin( lOmg/L) for 90 minutes ;6. c group:no ET' s stimulation after being perfused by kreb' s solution with heparin( 10mg/L)for 90 minutes. After preparation of isolated perfused kidney model, rat kidneys were perfused at a constant flow. Responses were consecutively measured as changes in perfusion pressure (mmHg) with polygraph amplifier console. After perfusion, kidney tissues were examined for I IP3R distribution with immunohistochemical staining and renal histological changes were observed with hematoxylin/eosin.RESULTSIn A group ( control group) , addition of 2nmol/L ET to perfusate caused an increase in perfusion pressure of 47 9 mmHg; In B group ( TNF- treatment group ) , TNF-a { 1 g/L ) didn' t modify baseline perfusion pressure, but caused an increase in perfusion pressure of 97 36 mmHg after ET' s stimulation. In C group ( heparin treatment group) , heparin also didn' t modify baseline perfusion pressure, but only caused an slight increase in perfusion pressure of 11 卤 6mmHg after ET' s stimulation. The differences in these three groups were very significant, P <0. 01. No pathological damages were found in kidney tissues from all groups after being stained with hematoxylin/eosin. The levels of I IP3R distribution with immunohistochemical staining in b group were higher than those of a group, the difference was significant, P <0. 05. While the levels of I IP3 R distribution in c group were not found less than those of a group, the difference was not significant, P >0. 05.CONCLUSION1. TNF-a may increase the renal vascular vasoconstriction responses to en-dothelin ( ET ).2. TNF-a can enhance the expression of type I inositol 1,4,5 - triphos-phate receptors (IP3 R) in glomerular mesangial cells and vascular smooth muscle cells.