Hemolysate-mediated renal vasoconstriction and hypersensitization.

The present studies measured vessel diameter, before and after addition of hemolysate, in isolated afferent arterioles (AA) and efferent arterioles (EA) obtained from the rat kidney. Human red blood cells (RBC) were hemolyzed in distilled water and membranes were discarded after centrifugation. Hemolysate added to the bath solution caused vigorous AA and EA contraction and, after washout, hypersensitized the AA and EA to doses of angiotensin II (AII) which would normally only elicit 50% contraction (EC50). Neither the contraction nor the hypersensitization were mimicked by pure human hemoglobin. The vasoconstrictive responses in the AA and EA were accompanied by increased cytosolic-free calcium concentration. Further purification (desalting) of the hemolysate to remove substance of < or = 1000 Da (which include ATP) did not eliminate the vasoconstrictive component from the hemolysate. Finally, cultured rat aortic vascular smooth muscle cells also demonstrated a rapid increase in (Ca2+i) when exposed to hemolysate. This increase in (Ca2+i) was, in part, dependent on Ca2+ influx since it could be attenuated with diltiazem (10(-5) M). In conclusion, hemolysate contains a factor which induces contractions of the isolated rat kidney AA and EA and rapid elevations in (Ca2+i). This factor, from hemolyzed RBC, is not hemoglobin itself.

Anaritide in acute tubular necrosis. Auriculin Anaritide Acute Renal Failure Study Group.

BACKGROUND: Atrial natriuretic peptide, a hormone synthesized by the cardiac atria, increases the glomerular filtration rate by dilating afferent arterioles while constricting efferent arterioles. It has been shown to improve glomerular filtration, urinary output, and renal histopathology in laboratory animals with acute renal dysfunction. Anaritide is a 25-amino-acid synthetic form of atrial natriuretic peptide. METHODS: We conducted a multicenter, randomized, double-blind, placebo-controlled clinical trial of anaritide in 504 critically ill patients with acute tubular necrosis. The patients received a 24-hour intravenous infusion of either anaritide (0.2 microgram per kilogram of body weight per minute) or placebo. The primary end point was dialysis-free survival for 21 days after treatment. Other end points included the need for dialysis, changes in the serum creatinine concentration, and mortality. RESULTS: The rate of dialysis-free survival was 47 percent in the placebo group and 43 percent in the anaritide group (P = 0.35). In the prospectively defined subgroup of 120 patients with oliguria (urinary output, < 400 ml per day), dialysis-free survival was 8 percent in the placebo group (5 of 60 patients) and 27 percent in the anaritide group (16 of 60 patients, P = 0.008). Anaritide-treated patients with oliguria who no longer had oliguria after treatment benefited the most. Conversely, among the 378 patients without oliguria, dialysis-free survival was 59 percent in the placebo group (116 of 195 patients) and 48 percent in the anaritide group (88 of 183 patients, P = 0.03). CONCLUSIONS: The administration of anaritide did not improve the overall rate of dialysis-free survival in critically ill patients with acute tubular necrosis. However, anaritide may improve dialysis-free survival in patients with oliguria and may worsen it in patients without oliguria who have acute tubular necrosis.

Abnormal vascular function following ischemia-reperfusion injury.

Ischemia-reperfusion injury as a general rule is accompanied by dramatic changes in basal and reactive vascular function in most organs. There are similarities in altered organ vascular function, particularly in the first 24 to 48 hours, with decreased basal organ blood flow, hypersensitivity to vasoconstrictor stimuli, attenuated responses to vasodilators, and increased vascular permeability. The reduced responsiveness to endothelium-dependent vasodilators may be due to reduced endothelial NOS activity or to spontaneous maximal activation of NOS/NO activity, which cannot be stimulated further by endothelium-dependent agents. There are also notable quantitative and qualitative differences in ischemia-reperfusion injury vasoreactive response in organs such as kidney, heart, and brain, the basis of which is unexplored, but may reflect regional differences in endothelium and/or organ parenchyma. Further examination of both the mechanisms and consequences of ischemia-reperfusion injury to the vasculature, as well as the clinical implications, should be a rewarding pursuit in organ pathophysiology.

Interventions in clinical acute renal failure: what are the data?

A variety of therapeutic approaches have been used both to prevent acute ischemic and nephrotoxic renal injury and to improve renal function and reduce mortality once acute renal failure (ARF) has developed. Unfortunately, there have been few rigorous assessments of the efficacy of these treatment interventions. The reasons for the lack of abundant critical data regarding treatment effects in ARF are several. First, ARF is a functional disorder. It has a spectrum of etiologies, occurs in a variety of clinical settings and varies in severity. Second, selected endpoints of treatment success vary and co-morbid factors frequently determine outcome. Third, it had been difficult to carry out prospective controlled studies in a disorder in which the mortality rate approaches 50%. In this review, an effort was made to analyze the available literature with a primary focus on controlled studies to determine significant prophylactic and treatment effects of various interventions in ARF. Three endpoints of therapy (change in renal function, change in course of azotemia, and change in mortality) were examined for pharmacologic agents. Changes in course of azotemia and mortality were assessed in evaluating different dialysis modes. Effect on nitrogen balance, change in course of azotemia, and change in mortality were used as endpoints to determine treatment effects of different nutritional regimens. When weight was given to prospective controlled studies, some insights emerged as to treatment interventions that are most likely to have beneficial effects in specific settings of ARF. Among pharmacologic agents, mannitol appears to have a positive prophylactic effect in kidney transplantation. There are no other significant beneficial effects of diuretics for prophylaxis or as treatment in early or established ARF. Of vasoactive agents, there is a relatively small amount of data suggesting that diltiazem may have a positive prophylactic effect in kidney transplantation, and dopamine possibly is beneficial early in the evolutionary phase of ARF. Atrial natriuretic peptide and calcium channel blockers may have beneficial effects in established disease. No other pharmacologic interventions are supported by substantial data. At best, the results are equivocal regarding the use of early and vigorous dialysis in ARF. However, there are recent impressive data indicating that the use of biocompatible membranes is efficacious in recovery and survival. There is no clear evidence that one form of nutritional therapy has advantages over others, but some level of amino acid supplementation in addition to basic energy replacement is supported by the overall data.

Is parenteral nutrition therapy of value in acute renal failure patients?

A patient with oliguric acute renal failure (ARF) following mitral valve surgery is presented. The patient was treated with parenteral nutrition and hemodialysis. While the patient survived, there were several complications of nutrition therapy. In this review, the benefits, risks, and uncertainties regarding parenteral nutrition in ARF are considered. First, the differences in metabolism in complicated and uncomplicated acute uremia are discussed. The important roles of alterations in intermediary metabolism and of proteases in the catabolism of ARF are emphasized. The historical basis of parenteral nutrition treatment in ARF is reviewed. The results are divided regarding the relationship among nutritional support, improvement in renal function, and enhanced patient survival. A critical analysis of nitrogen metabolism results reported in the literature does not convincingly support the effectiveness of parenteral nutrition formulae in generating positive nitrogen balance. The complications of parenteral nutrition therapy are outlined. In light of the uncertain efficacy and recognized risks of prolonged parenteral nutrition, a rationale for approaching therapy is presented that is based on the estimated metabolic stress and protein-energy requirements of the individual ARF patient.

Sequential agonist activation and site-specific mediation of acute cyclosporine constriction in rat renal arterioles.

Evidence suggests that acute and chronic cyclosporine (CsA) nephropathy may be related to its renal vasoconstrictor effects. While the mechanism of CsA-induced renal vasoconstriction is uncertain, several studies indicate that endogenous constrictor agonists including endothelins (ET), platelet activating factor (PAF), and thromboxane A2 (TXA2) play a mediating role. In this study, two possible mechanisms explaining the participation of multiple constrictor agonists in CsA vasoconstriction were investigated: sequential activation of agonists initiated by CsA and site-specific mediation of CsA constriction by different agonists. The acute constrictor effects of CsA were examined in isolated rat renal afferent (AA) and efferent arterioles (EA) without and with specific receptor antagonists of ETA (BQ123, 10(-7) M), PAF (L-659,989, 10(-7) M), and TXA2/PGH2 (SQ29,548, 10(-7) M) in the bathing media. Both BQ123 and L-659,989 completely inhibited CsA, constriction in AA, but had no significant inhibiting effect in EA. Constriction to ET-1 was also blocked by the PAF antagonist L-659,989 in AA, but not EA. There was no effect of SQ29,548 on CsA constriction in AA--however, there was partial attenuation of CsA constriction in EA. Based on these results in isolated rat renal arterioles, it is suggested that CsA-induced constriction in AA is likely mediated by sequential activation of ET and PAF. However, CsA constriction of EA involves a different mechanism or mediator that, in part, may involve TXA2/PGH2 stimulation.

Endothelial regulation of vascular tone.

Through the release of a variety of relaxing and contracting factors, including nitric oxide and endothelin-1, the endothelium exerts a complex paracrine influence on vascular smooth muscle cells. Dysfunction of these mechanisms for regulating tone may have relevance to various clinical entities, including hypertension, atherosclerosis, renal failure, and diabetes.

Effects of ANG II, ETA, and TxA2 receptor antagonists on cyclosporin A renal vasoconstriction.

The renin-angiotensin system, endothelin (ET), and vasoconstrictor prostaglandins have been reported in separate studies to mediate the renal vasoconstrictor effect of cyclosporin A (CsA). However, direct comparison of the relative importance of these potential mediators has not been performed. In this study, the attenuating effects of comparable agonist-inhibiting doses of receptor antagonists for angiotensin II (ANG II), DuP-753 at 2.5 mg/kg, for ETA, BQ-123 at 0.5 mg/kg, and for thromboxane A2 (TxA2), SQ-29,548 at 1.6 mg.kg-1.h-1, or saline vehicle on acute CsA (20 mg/kg) renal vasoconstriction were compared in anesthetized Sprague-Dawley rats. All three receptor antagonists significantly limited the CsA-induced increase in renal vascular resistance; however, BQ-123 and SQ-29,548 were more effective than DuP-753. Because all three receptor antagonists demonstrated at least some attenuation of CsA-induced renal vasoconstriction, the potential role of acute CsA-related nitric oxide synthase (NOS) inhibition and nonspecific heterologous effects of specific receptor antagonists on other agonists were determined to exclude the possibilities that there was a general increased agonist sensitivity and that detection of a single or primary constrictor mediator was obscured by "crossover" receptor antagonist effects. CsA significantly reduced renal blood flow (39%) in the presence of the NOS inhibitor, N omega-nitro-L-arginine methyl ester, and there was negligible indication that receptor antagonists had nonspecific effects. It is concluded that CsA-induced renal vasoconstriction is complex and involves activation of multiple constrictor agonists independently or sequentially.

Responses to hemorrhagic arterial pressure reduction in different ischemic renal failure models.

Renal blood flow (RBF) autoregulation has been found to be impaired in both norepinephrine (NE) and renal artery clamp (RAC) rat ischemic acute renal failure models. However, the decline in RBF at the normal lower limit of autoregulation is greater in NE-ARF. The present study was designed to determine if this difference in autoregulatory profiles has potential functional and morphologic significance. After demonstrating a fall in RBF to renal perfusion pressure reduction to 90 mm Hg that was twofold more in one week NE- than RAC-ARF (p < 0.001), separate rats of both ischemic ARF types with nearly identical levels of azotemia and glomerular filtration rate reduction and sham-ARF rats were subjected to four-hour controlled reduction in mean arterial pressure to 90 by transient phlebotomy at one week. On day 9, two days after mean arterial pressure reduction, blood urea nitrogen (BUN), serum creatinine (SCr) and creatinine clearance (CCr) showed continued improvement in RAC-ARF, but there were significant increases in BUN (46 +/- 22 to 72 +/- 10 mg/dl) and SCr (1.2 +/- 0.2 to 1.5 +/- 0.2 mg/dl) and a decline in CCr (0.434 +/- 0.127 to 0.334 +/- 0.079 ml/min) in the NE-ARF group (all P < 0.02). The mean sum of scores of morphologic indices of ARF was higher in NE- than RAC-ARF kidneys of rats sacrificed on day 9 but interstitial edema was the only individual index that was worse in NE-ARF.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of atrial natriuretic peptide in clinical acute renal failure.

Fifty-three consenting patients meeting clinical and urine composition criteria for established intrinsic ARF were assigned to two treatment groups. Group I patients were treated with human atrial natriuretic peptide (ANP) with or without diuretics. Groups II patients were treated with or without diuretics and with no ANP. Age, sex, etiology of ARF, entry serum creatinines (SCr) (Group I, 5.3 +/- 1.8; Group II, 5.1 +/- 2.1 mg/dl) and creatinine clearances (CCr) (Group I, 9.9 +/- 2.1; Group II, 9.2 +/- 2.1 ml/min) were similar. Thirty patients received ANP [0.20 micrograms/kg/min i.v. x 24 hr (N = 20) or 0.08 micrograms/kg/min i.a. x 8 hr (N = 10)] and furosemide, 0.5 mg/kg/hr x 24 hr or mannitol, 12.5 g every six hours x 4, or no diuretic; 23 Group II patients received diuretics as above or no diuretic in a similar distribution to Group I. CCr (verified with simultaneous inulin clearances x 12, r = 0.93, P < 0.001) increased significantly by eight hours of ANP treatment to 17.1 +/- 3.2 ml/min and by 24 hours after discontinuing ANP to 21.0 +/- 4.4 ml/min (both P < 0.05). There was no corresponding increase in CCr in Group II. Dialysis was required in 23% of Group I and in 52% of Group II patients (different at P < 0.05). Mortality rates of 17% for Group I and 35% for Group II were not significantly different (P = 0.11). It is concluded that parenteral ANP increases CCr and reduces need for dialysis in patients with established intrinsic ARF.

Glomerular and tubular factors in urine flow rates of acute renal failure patients.

Distinguishing between oliguric and nonoliguric acute renal failure (ARF) has clinical relevance. However, there is a paucity of data regarding the pathophysiologic basis for variations in urine flow rates in ARF. This study was designed to determine whether differences in residual levels of glomerular filtration rate (GFR) or differences in tubular reabsorption of filtered solutes and H2O accounted for the variations in urine flow rates among ARF patients. Twenty-five patients with ARF of 3 to 6 days duration having ischemic and nephrotoxic etiologies, increasing serum creatinines of more than 0.7 mg/dL/d, urine sodium concentrations and fractional excretions of sodium (FENa) of more than 20 mEq/L and more than 1%, respectively, 12 hours after stopping diuretics and urine sediments consistent with acute tubular necrosis were studied. Urine and serum collections were made over an 8-hour period to determine creatinine clearance (Ccr), filtered osmolar load, urine to serum creatinine ratio (U/Scr), urine to serum creatinine osmolality (U/Sosm), and FENa. These were compared with urine flow rates. Creatinine clearance was validated as an estimate of GFR in ARF with simultaneous inulin clearances x 12 measurements (r = 0.935, P < 0.001). Residual Ccr was strongly correlated with urine flow rate (r = 0.857, P < 0.001), as was filtered osmolar load (r = 0.810, P < 0.001). However, the latter relationship was totally dependent on Ccr. There was no correlation between U/Scr, U/Sosm, or FENa and urine flow rates. It is concluded that the residual level of GFR is the primary determinant of variations in urine flow rate in patients with ARF.

Effects of endothelin receptor antagonist on cyclosporine-induced vasoconstriction in isolated rat renal arterioles.

Recent evidence suggests that the potent constrictor peptide, endothelin (ET) has a mediating role in cyclosporine A (CsA)-related renal vasoconstriction. However, the nature of the CsA-ET interaction and effect on the renal vasculature is uncertain. The purpose of the present study was twofold: (a) to determine if CsA exposure caused direct local release of ET from the endothelium of the renal microvasculature and (b) to determine if locally generated ET has paracrine effects on the underlying vascular smooth muscle to induce vasoconstriction. Experiments were performed in isolated rat renal arterioles. First it was determined that both afferent arteriole (AA) and efferent arteriole (EA) exhibited concentration-dependent decreases in lumen diameter to increasing molar concentrations of CsA. The AA was more sensitive to the vasoconstrictive effects of CsA than the EA. Next, the blocking effect of a recently synthesized putative ETA receptor antagonist was verified in both the AA and EA, where it was found that the cyclic peptide cyclo D-Asp-L-Pro-D-Val-L-Leu-D-Trp totally inhibited the vasoconstriction observed with ET addition. Finally, the role of locally stimulated ET in CsA-induced vasoconstriction was tested by determining the effect of the ETA receptor antagonist on CsA-induced AA and EA constriction. In the AA the vasoconstrictor effect of 10(-11) M CsA was completely blocked by the ETA receptor antagonist. However, in contrast to AA, 10(-11) M CsA in EA in the presence of the ETA receptor antagonist decreased EA lumen diameter by a mean of 41% from baseline (4.80 +/- 0.75 microns vs 7.80 +/- 0.84 microns, P < 0.05). This change in lumen diameter was similar to that induced by CsA alone. These data suggest that CsA directly constricts renal microvessels. This effect is mediated by ET in the AA but not the EA.

Angiotensin II-induced changes in smooth muscle calcium in rat renal arterioles.

The isolated rat renal arteriole technique was adapted for use in a fluorescence ratio imaging system in which angiotensin II (AII)-induced changes in lumen diameter and smooth muscle cell (SMC) cytosolic calcium [(Ca2+]i were serially determined for 4 min with Fura-2. Selective fluorescence acquisition from SMC was guided by direct image visualization of the vessel walls. A maximal constricting concentration of AII (10(-8) M) caused similar abrupt and sustained increases in SMC [Ca2+]i in afferent arterioles (AA) at 80 mm Hg and efferent arterioles (EA) at 30 mm Hg. When lumen pressure was reduced to 0 mm Hg, 10(-8) M AII caused abrupt peak increases in SMC [Ca2+]i in 15 s in both AA and EA, which declined rapidly thereafter--patterns distinctly different from pressurized vessels (P < 0.02). With diltiazem (10(-5) M) in the bathing media, 10(-8) M AII caused an abrupt rise and decline in SMC [Ca2+]i in AA, but a sustained elevation in EA (P < 0.02). In low-Ca(2+)-EGTA media, there was an abrupt peak and rapid decline in SMC [Ca2+]i to 10(-8) M AII in AA and EA; the abrupt peaks were attenuated by the prior addition of dantrolene (5 x 10(-5) M) to the low-Ca(2+)-EGTA media. When half-maximal constricting (EC50) AII for AA (4 x 10(-11) M) was added, there was a slow, progressive increase in SMC [Ca2+]i that was distinctly different from the abrupt peak and decline with EC50 AII (5 x 10(-12) M) in EA. Collectively, these findings indicate that maximal AII stimulates both Ca2+ entry and storage mobilization in AA and EA; EC50 AII stimulates primarily Ca2+ entry in AA, but storage mobilization in EA. Lumen pressure modifies the AII SMC [Ca2+]i response profiles.

Maintenance of endothelin-induced renal arteriolar constriction in rats is cyclooxygenase dependent.

Influence of arachidonate cyclooxygenase (COX) products on endothelin (ET)-evoked renal vasoconstriction was assessed. In microperfused rat afferent (AA) and efferent arterioles (EA), indomethacin had no effects on the maximal contraction of both AA and EA by ET, but reduced the duration of ET-induced constriction in both arterioles. ET infusion to rats in vivo resulted in a selective increase in efferent but not afferent arteriolar resistance, leading to a dramatic increase in transcapillary hydraulic pressure difference. Glomerular filtration rate (GFR), which fell progressively during infusion of ET alone, was markedly preserved by COX inhibition, but not during selective thromboxane A2 antagonism. In isolated glomeruli, release of prostaglandin (PG) F2 alpha in response to 10(-6) mol/l ET exceeded that the PGE2 by a ratio of 3.2. Collectively, these data provide strong evidence that locally released COX products, possibly PGF2 alpha, play a key role in sustaining ET-induced renal arteriolar constriction. COX inhibition leads to acute vasorelaxation of AA despite continued ET administration, without affecting EA constriction in vivo, thereby resulting in a dramatic reversal of the effects of ET on GFR.

Analysis of the repertoire of human B-lymphocytes specific for type A and type B blood group terminal trisaccharide epitopes.

Naturally occurring serum antibodies specific for the A and B blood group isoantigens are of great importance in medicine. By using A-type terminal trisaccharide (ATS) or B-type terminal trisaccharide (BTS) coupled to albumin as coating antigens, an enzyme-linked immunosorbent assay capable of detecting all ATS/BTS-binding antibodies was performed. The combination of this enzyme-linked immunosorbent assay with limiting-dilution methodology, using a polyclonal B-lymphocyte activator, permitted a monoclonal analysis of the human antibody repertoire that is specific for ATS and BTS in persons of different blood types. Most (78%) positive supernatants from type O cultures were monospecific for either ATS or BTS, and these were present at roughly equivalent frequencies. Nine supernatants with reactivity toward both ATS and BTS were tested by red cell adsorption; six had properties expected for true dually reactive monoclonal antibodies: adsorption with either A1 or B red cells eliminated both anti-ATS and anti-BTS activity. This finding accords with a monoclonal origin for anti-A,B. The analysis of cultures of peripheral blood lymphocytes from type A and B donors unexpectedly showed significant numbers of clones with apparent autospecificity. However, none of the anti-ATS-positive supernatants from type A cultures or anti-BTS-positive supernatants from type B cultures were adsorbable with A1 or B red cells, respectively. Consideration of only true (adsorbable) positives indicates that the type A and B anti-trisaccharide repertoires differ significantly from the type O repertoire, probably as a result of the action of normal self-tolerance mechanisms.

KCl and angiotensin responses in isolated rat renal arterioles: effects of diltiazem and low-calcium medium.

Studies in intact renovascular models have shown that calcium entry blockers inhibit angiotensin (ANG II)-induced vasoconstriction in afferent (AA) but not efferent arterioles (EA), suggesting that increases in smooth muscle cell cytosolic calcium, the initiating intracellular message, result from entry through potential-operated channels in AA, but from organelle storage mobilization or entry through nonpotential-operated channels in EA. The present study examined the effects of diltiazem (10(-5) M) on the constrictor responses to KCl (50 mM) and half-maximal constricting concentrations (EC50) of ANG II and the effects of low-calcium bathing medium on EC50 ANG II responses in isolated rat AA and EA. KCl caused slightly greater decreases in lumen diameter in AA than in EA (P < 0.05) that were completely inhibited by diltiazem in both. Vasoconstriction to ANG II was significantly inhibited by diltiazem (29 +/- 12 vs. 67 +/- 31%; P < 0.02) in AA. However, constrictor response to ANG II in EA was unchanged by diltiazem (42 +/- 32 vs. 41 +/- 31%). Constriction to ANG II of AA in low-calcium medium was significantly attenuated (8 +/- 13 vs. 54 +/- 12%; P < 0.01); however, EA constrictor response was not affected (43 +/- 22 vs. 51 +/- 19%). These data indicate that EC50 ANG II-induced AA constriction requires calcium entry primarily through potential-operated channels. While potential-operated calcium entry channels can be functionally expressed in EA, intracellular calcium mobilization is the primary mechanism for ANG II-induced constriction.

Comparative sensitivities of isolated rat renal arterioles to endothelin.

The specific intrarenal sites and mechanism of endothelin (ET) vascular action are controversial. In this study afferent (AA) and efferent arterioles (EA) were isolated from the kidneys of normal Sprague-Dawley rats. Their respective concentration-dependent changes in lumen diameter in response to ET-1 were compared with those of angiotensin II (ANG II) and norepinephrine (NE). In a second series of experiments, the duration of vasoconstriction to comparable transient submaximal ET-1, ANG II, and NE concentrations in AA and EA was examined. The role of angiotensin II in mediating endothelin vasoconstriction also was examined with the converting-enzyme inhibitor captopril (CAP) and the competitive inhibitor [Sar1,Ala8]ANG II (SAR). The half-maximal constriction concentration (EC50) of ET-1 was less in EA than AA (P < 0.01). EC50 of ET-1 in AA was similar to that of ANG II, but was less than that of NE (P < 0.001). In EA the EC50 of ET-1 was also similar to that of ANG II, but much less than that of NE (P < 0.001). In both AA and EA the duration of ET-1 constriction was at least twice that of ANG II and more than fivefold that of NE. Neither CAP (10(-6) M) nor SAR (10(-7) M) changed the vasoconstrictor response to submaximal concentrations of ET-1 in AA or EA. It is concluded that ET-1 is a potent and prolonged constrictor agonist with a small, but significantly greater, concentration-dependent effect in EA than AA. The constrictor effect of ET-1 does not require ANG II activity.

Correlation of antibody multireactivity with variable region primary structure among murine anti-erythrocyte autoantibodies.

A high proportion of the antibodies in the preimmune repertoire bind to several unrelated antigens and are considered to be multireactive. This property is reportedly associated with the antibodies produced by CD5+ B lymphocytes. Because many antibodies specific for bromelain-treated mouse red blood cells (BrMRBC) derive from CD5+ B cells, we tested monoclonal antibodies of this specificity for multireactivity. Two variable region combinations, VH11/V kappa 9 and VH12/V kappa 4, account for greater than 80% of this repertoire, but none of these antibodies exhibited a multireactive phenotype. In contrast, three anti-BrMRBC binding antibodies belonging to the J558 family (BrM1, BrM8, and CH12) showed varying degrees of multireactivity, and bound both highly negatively and positively charged antigens. The amino acid sequences of the VH regions of these antibodies are highly homologous (greater than 85% identical) and they possess large VH-D-J junctions with extensive N-region insertions. The kappa chains of two of these antibodies utilize an identical V kappa gene segment, while the third uses a very different V kappa with only 50% homology. The entire H chain V regions of these antibodies are unusually basic, with isoelectric points of 9.5-10, a feature which might be important in promoting interactions with acidic epitopes. The multireactive antibodies also contain regions with a high concentration of hydroxylside chain amino acids, especially in their VH-D-J junctions. This region also contains acidic amino acid residues, which may be important in binding of positively charged epitopes. We propose that an open, accessible binding site and a charge polarity may be features which facilitate the binding of charged epitopes, providing a structural basis for multireactivity of at least some antibodies.

Renal vasculature and ischemic injury.

Functionally similar ischemic acute renal failure (ARF), as estimated by glomerular filtration rates (GFR), was induced by renal artery clamping (RAC) or intrarenal norepinephrine (NE) in rats and renovascular reactivity was examined at 1 week. With RAC-ARF induction there was total renal ischemia followed by abrupt return of renal blood flow (RBF). With NE-ARF induction there was subtotal ischemia (10-15% of basal RBF) with RBF recovery over several hours. Renovascular resistance (RVR) did not change to renal perfusion pressure (RPP) reduction in the autoregulatory range in RAC-ARF but paradoxically increased in NE-ARF. There was an exaggerated response to renal nerve stimulation in NE-ARF but no response in RAC-ARF. There was a vasoconstrictor response to intrarenal norepinephrine in the former but a negligible response in the latter. There was no vasodilation to acetylcholine in either group, but there was a normal response to prostacyclin in NE-ARF. Smooth muscle necrosis was found in 46% of resistance arterial vessels in RAC- but in only 8% of NE-ARF (p less than .001). When mean arterial pressure was reduced to 90 mm Hg for 4 h at 1 week, recurrent azotemia and fresh ischemic injury were noted in NE- but not RAC-ARF. It is concluded that different models of ischemic ARF induction result in different patterns of abnormal postischemic vascular reactivity. Differences in vascular smooth muscle and endothelial injury are due to differences in initial ischemia or rates of postischemic reperfusion.