Cortical interstitial cell interactions induce sensitivity of hydronephrotic kidney to bradykinin

Thromboxane A2 receptor blockade improves renal function and histopathology in the post-obstructive kidney

To elucidate the role of the vasoconstrictor thromboxane A2(TXA2) in post-obstructive nephropathy, we examined the effect of the TXA2 receptor antagonist GR32191(GR) on renal function and histopathology in the post-obstructed kidney (POK) in rats. Rats pre-treated with 3 or 6 mg/kg i.p. of GR prior to ureteral obstruction and maintained on b.i.d. doses of GR were compared to vehicle-treated and sham-operated controls. Renal hemodynamic, clearance and excretory function were assessed in each kidney following relief of 24 hours of unilateral ureteral obstruction. The histology of each kidney was evaluated. Mean clearances of inulin for the POK were significantly greater in the treated rats (0.42 +/- 0.06 ml/min at 6 mg/kg) than in controls (0.13 +/- 0.04 ml/min) and a dose-response effect was observed (P < 0.05). Paraaminohippurate clearance was increased by > 150% and renal vascular resistance was reduced by 50% in GR treated animals compared with controls (P < 0.05). Histopathologic findings in the untreated POK were typical of early obstruction. In the GR treated groups these changes were much less severe. These data support an important role for TXA2 in the pathogenesis of post-obstructive nephropathy.

The effect of stones on renal and ureteric physiology

The effect of calculi on renal and ureteric function is the result of a complex sequence of pathophysiological events triggered by obstruction. The degree of impairment of renal function resulting depends on whether the obstruction is partial or complete, is unilateral or bilateral, is complicated by infection or not and how and when it is relieved. This review will look at these interacting factors and particularly on the effects of various treatment modalities ranging from open techniques to minimally and non-invasive interventions.

Tubulointerstitial nephritis

Tubulointerstitial nephritis (TIN) describes a range of pathological processes that are at least partly responsible for the progression of renal disease of nearly all aetiologies. TIN is frequently the most important pathological manifestation of progressive glomerulonephritis, obstructive uropathy, reflux nephropathy and cystic diseases, although it may also present as a primary disease process associated with infection, drug use or other immunologically mediated disease. Recent clinical and laboratory research has increased our knowledge of tubulointerstitial structure, physiological function and tubulointerstitial response to injury. This review presents a classification of TIN in which acute and chronic tubulointerstitial diseases are recognized as forming a continuum. Primary TIN and TIN associated with glomerulonephritis, obstructive nephropathy and chronic progressive renal disease are discussed from both clinical and pathogenic aspects. It is argued that chronic TIN is a disease process in which inflammation is accompanied by a destructive tubulopathy and fibrogenesis. In acute TIN there is a cessation and reversal of this process. It is suggested that most forms of TIN have an immunological basis because of the presence of immune cell infiltrates, the occurrence of TIN in several immune diseases and immunological animal models of TIN. However, to date TIN has not been convincingly modified in patients by immune manipulation. Experimental evidence suggesting an important pathogenic role for proteinuria and antigenuria, and the renal tubule cell acting as an antigen-presenting cell is discussed.

Acute renal failure due to urinary tract obstruction

Urinary tract obstruction is a frequent cause of acute renal failure that is potentially life threatening but reversible, if it is promptly recognized and corrected. The level of urinary tract obstruction is variable, dependent on the underlying disease, and may range from the loop of Henle to the urethral meatus. Clinical manifestations are most commonly due to renal failure, but the history and physical examination can aid in determining the localization and cause of the obstruction. Laboratory findings may suggest urinary tract obstruction as the etiology for acute renal failure. Radiologic procedures, most prominently ultrasonography, can establish the diagnosis. Treatment is variable, but patient management may need to be altered during the postobstructive phase of urinary tract obstruction owing to physiologic response to reestablishment of urine flow.

Epidermal growth factor stimulates phospholipase A2 in vasopressin-treated rat glomerular mesangial cells

Epidermal growth factor (EGF) enhances vasopressin- and ionophore-A23187-induced prostaglandin production and arachidonate release by rat glomerular mesangial cells in culture. The purpose of the present study was to delineate the phospholipid pathways involved in this effect. In cells labelled with [14C]arachidonate, EGF significantly enhanced the free arachidonate released in response to A23187 or vasopressin without enhancing the production of [14C]arachidonate-labelled diacylglycerol. EGF increased the [14C]arachidonate-labelled phosphatidic acid formed in response to vasopressin, but to a much smaller extent than it increased free arachidonate release. These results indicate that activation of phospholipase C is not sufficient to explain the increase in free arachidonate release observed on addition of EGF. To examine if EGF enhanced phospholipase A2 activity, mesangial cells were labelled with [2-2H]glycerol and [14C]-arachidonate, and the formation of arachidonate-poor lysophospholipids was studied. When combined with vasopressin, EGF significantly enhanced the formation of arachidonate-poor lysophospholipids as compared with vasopressin alone. The fate of exogenously added lysophosphatidylcholine was not altered after stimulation with vasopressin plus EGF, indicating that decreased deacylation or reacylation of the lysophospholipids was not responsible for their accumulation. Taken together, these results indicate that EGF enhances free arachidonate release by activation of phospholipase A2. The signalling mechanism responsible for the change in phospholipase A2 activity is not known, but could conceivably involve phosphorylation of modulating proteins such as lipocortin or G-proteins.