Oxidant stress following renal ischemia: changes in the glutathione redox ratio

Pretreatment of animals with certain antioxidant enzymes and substances decreases renal damage following ischemia and reperfusion. The hypothesis that reoxygenation imposes an oxidant stress has been used to explain this. The present study has directly assessed oxidant stress under these conditions by measuring the glutathione redox ratio ([GSSG/(GSH + GSSG)] x 100) in freeze-clamped kidney. The glutathione peroxidase system plays a role in removing peroxides which result from oxidant stress, generating GSSG from GSH in the process. The selenium-dependent glutathione peroxidase can metabolize H2O2 and other hydroperoxides. A non-selenium-dependent glutathione peroxidase activity is present and can metabolize organic hydroperoxides, but it cannot metabolize H2O2. Under anesthesia, the left renal artery was occluded for 40 minutes and then reflow was allowed. Kidneys were freeze clamped before reflow and after 5, 10, and 15 minutes of reflow. The contralateral kidney was freeze clamped and used as a control. The control value for the glutathione redox ratio was 1.09 +/- 0.05. This fell during ischemia to 0.67 +/- 0.22 and increased significantly to 1.66 +/- 0.29 after five minutes of reperfusion. By 15 minutes it had returned to 1.09 +/- 0.22. Treatment of rats with diquat, which causes a severe oxidant stress, raised the glutathione redox ratio from 0.88 +/- 0.12 to 1.89 +/- 0.15. Thus, reperfusion was concluded to cause a large but transient oxidant stress. Selenium-deficient rats were used to examine the nature of the oxidant stress. Activity of the selenoenzyme glutathione peroxidase was depressed to 2% of control in the kidneys of these rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of fluoridated sucrose on rat caries

The present study was designed to test the effect of frequent pulses of low fluoride levels on rat caries when supplied in a standardized cariogenic rat diet containing 67% sucrose (MIT-200). The test diets were variants of Diet MIT-200 in which the sucrose component had been fluoridated with NaF solution resulting in total concentrations of 0 (control), 2, 3, 5, 10, or 20 ppm fluoride in the final diets. Rats received one of the test lots 17 times daily in a programmed feeding machine beginning at age 22 days, and were inoculated with Streptococcus mutans at age 23, 24, and 25 days. After 5 weeks, the rats were sacrificed and their mandibular molars scored for number and severity of sulcal, buccolingual, and proximal caries. Frequent daily pulses of as little as 2 ppm fluoride in dietary sucrose were effective in significantly (p less than 0.01) reducing buccolingual rat caries.

Atrial natriuretic peptide, right atrial pressure, and sodium excretion rate in the rat

This study examined the relationship between right atrial pressure (RAP), urine flow rate, sodium excretion rate, and plasma atrial natriuretic peptide (ANP) levels after an acute Ringer expansion. Two groups of rats had their RAP monitored and balloon catheters placed in their thoracic inferior venae cavae. In one group the balloon remained deflated, and in the second group the balloon was inflated during the volume expansion in an attempt to prevent the rise in RAP. The peak RAP was 7.3 +/- 0.8 mmHg when the balloon remained deflated and 3.5 +/- 0.6 mmHg in the group with the balloon catheter inflated (P less than 0.005). The corresponding peak ANP levels were 682 +/- 140 and 223 +/- 40 pg/ml. There was a significant correlation between the peak RAP and ANP levels (r = 0.754; P less than 0.05). The inflation of the balloon catheter significantly decreased the urine flow rate and the urine sodium excretion rate. A final group of animals had 200 microliters of rabbit serum containing antibody to ANP infused before the volume expansion. The antibody-treated animals had significantly lower urine flow and sodium excretion rates than nonantibody-treated control rats. We conclude that ANP is one of the factors which allows the rat to excrete an acute Ringer expansion.

Effect of chronic administration of different Bence Jones proteins on rat kidney

The role of Bence Jones proteins (BJPs) in the genesis of the renal dysfunction that develops in patients with multiple myeloma is not clearly defined. We previously evaluated renal function and morphology in a unique strain of rats (LOU/m) bearing tumors which synthesized BJPs with isoelectric points of 5.2, 4.3 and 6.7. Myeloma cast nephropathy developed in one tumor bearing group (pI 5.2), tubular necrosis was observed in another (pI 4.3), and renal function and histology remained normal in a third group (pI 6.7). To see if these renal outcomes were a function of the BJP being excreted or other factors which could be present in the tumor bearing animals, we have examined the effect of chronic intravenous administration of these three BJPs on renal function and histology in non-tumor-bearing LOU/m rats. Urine containing the BJP was collected from tumor bearing rats, sterilized by passage through a 0.2 mu millipore filter, concentrated to 50 mg/ml, and dialyzed extensively so as to remove material with a molecular weight less than 3500. Chronic indwelling-venous catheters were placed in non-tumor-bearing LOU/m rats and these rats were given 100 mg/day for five days of one of the three BJPs. Polyfructosan clearance (Cin) was measured prior to and following the five days of BJP administration. Renal histology was examined at the completion of the second Cin. In the pI 5.2 group (N = 6), a severe distal nephron cast nephropathy occurred and Cin fell from 2.88 +/- 0.24 to 0.90 +/- 0.17 ml/min (P less than 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

The role of high-energy phosphate in norepinephrine-induced acute renal failure in the dog

Previous studies have demonstrated that pretreatment with mannitol, furosemide, or bradykinin can attenuate the severity of norepinephrine-induced renal functional impairment. The present studies were designed to evaluate the possibility that these agents are protective, in part, by preserving cellular metabolic integrity. The renal cortex was repetitively biopsied during the course of this study, and high-pressure liquid chromatography was used to analyze the tissue content of adenine nucleotides (expressed in nanomoles per gram of wet tissue). The adenine nucleotide charge ratio (CR) and total adenine nucleotide (TAN) content were calculated as indices of cellular metabolic integrity. In addition to the above-established protective agents, phenoxybenzamine was used to evaluate a direct toxic effect of norepinephrine on renal tissue. Inulin clearance at 3 hours post infusion (expressed as a percent of control) was 7% with norepinephrine alone and, in the protected groups, 36% with bradykinin, 61% with furosemide, 51% with mannitol, and 100% with phenoxybenzamine. There was no change in CR or TAN with phenoxybenzamine. In contrast, during norepinephrine administration CR fell significantly in all other groups. Three hours after stopping norepinephrine, CR had returned toward control values and the level of CR was significantly better in all protected groups when compared with norepinephrine alone. Similarly, the levels of TAN were significantly diminished in the norepinephrine-alone group when compared to all protected groups, and there was significantly more tubular necrosis as well. The maintenance of higher levels of TAN and the preserved ability to regenerate adenosine triphosphate in the protected groups, when compared to the norepinephrine-alone group, support the contention that these agents offer protection, at least in part, by preserving cellular metabolic integrity.

Effect of atriopeptin II on determinants of glomerular filtration rate in the in vitro perfused dog glomerulus

Atrial natriuretic factor (ANF) is a peptide originally found to be present in extracts of mammalian atria that possess marked natriuretic and diuretic qualities. A number of mechanisms have been suggested to explain these properties. Recently, it has been suggested that ANF may enhance glomerular filtration. In this report, we describe a series of experiments designed to investigate if atriopeptin II, a 23-amino acid synthetic analogue of ANF, increases glomerular filtration rate (GFR) and, if so, the mechanism for this increase. We used the isolated perfused glomerulus technique (n = 6), which allows a single isolated glomerular unit to be perfused and the determinants of single-nephron GFR (SNGFR) to be measured. Two periods were performed in each experiment, the control followed by the experimental. The only difference between the two periods was the addition of atriopeptin II to the experimental perfusate at a final concentration of 5 X 10(-7) M. There was indeed a significant increase in the SNGFR (78 +/- 27 to 108 +/- 29 nl/min, P less than 0.01). This increase was associated with a significant increase in the glomerular capillary hydrostatic pressure (PGC) from 31 +/- 3 to 35 +/- 3 mmHg (P less than 0.05). The filtration fraction also increased in each experiment (from 0.16 +/- 0.3 to 0.25 +/- 0.03, P less than 0.005). Neither the afferent flow nor the efferent arteriolar flow changed, although there was a tendency for both to decrease.(ABSTRACT TRUNCATED AT 250 WORDS)

The assessment of the chemotherapeutic effects of vinca alkaloids by immunofluorescence and flow cytometry

The effects of the vinca alkaloids on the rates of DNA synthesis in the human pancreatic carcinoma line, MIA Pa Ca-2 have been studied by a new technique for measuring cell kinetics and DNA synthesis by flow cytometry and immunofluorescence. The method employs a monoclonal antibody that is highly specific for bromodeoxyuridine or iododeoxyuridine. The drugs vincristine and vindesine do not appear to have a direct effect on DNA synthesis rate across S phase, whereas DHAD, a compound that has been found previously to affect DNA synthesis, does appear by this technique to inhibit DNA synthesis at specific segments of S phase. That vincristine does not block cells in S phase by inhibiting DNA synthesis is borne out of the observation that cells blocked in S or G2 + M can still incorporate BrdUrd at a high rate in these phases of the cell cycle.

Effect of albumin on glomerular ultrafiltration coefficient in isolated perfused dog glomerulus

To evaluate the direct effect of albumin concentration on the glomerular capillary ultrafiltration coefficient (Kf), we compared the effect of "normal" (3.4 g/100 ml), "low" (0.1 g/100 ml), and "no albumin" (less than 0.005 g/100 ml) concentration on the determinants of single-nephron glomerular filtration rate (SNGFR) as measured with the isolated perfused glomerulus technique. When the albumin concentration was decreased from normal to low concentrations, the afferent flow rate increased from 318 +/- 147 (mean +/- SE) to 450 +/- 174 nl/min, the filtration fraction increased from 0.19 +/- 0.04 to 0.35 +/- 0.08, and the SNGFR increased from 49 +/- 21 to 126 +/- 34 nl/min. These changes were associated with a small though significant increase in Kf from 2.79 +/- 1.01 to 3.74 +/- 0.98 nl/(min X mmHg) (P less than 0.05). When the albumin concentration was decreased from low to no albumin the filtration fraction and SNGFR increased even further and were associated with a marked increase in Kf to a value of 27.04 +/- 11.43 nl/min X mmHg). We conclude that there is very little effect of decreases in albumin concentration on Kf until extremely low levels are reached, and at that point there is a marked increase in the ultrafiltration coefficient. Furthermore, when these extremely low concentrations of albumin are reached an important role for albumin in the basic function of the ultrafiltration barrier is demonstrable.

Role of volume depletion in the glycerol model of acute renal failure

Previous studies have demonstrated significant volume depletion early in the course of glycerol-induced acute renal failure. In addition, it has been shown that acute volume expansion within 6 h of glycerol administration reverses the fall in inulin clearance but volume expansion 12-24 h after glycerol fails to restore that parameter to normal. The current studies were performed to determine whether chronic volume expansion would prevent the fall in inulin clearance normally observed 18-20 h after the insult. Inulin clearance was therefore compared 18-20 h after glycerol in hydropenic rats and in rats undergoing chronic volume expansion by the constant infusion of Ringer solution at a rate of 5 ml/h initiated at the time of the glycerol injection. Inulin clearance was well maintained in the latter group, averaging 1.77 compared with 0.22 ml/min in the hydropenic group. Renal histology revealed no difference in the degree of tubular necrosis between groups but did show a marked decrease in cast formation in the animals undergoing chronic volume expansion. To determine the possible significance of these casts, micropuncture studies were carried out to measure proximal tubular pressures. Under hydropenic conditions these pressures were not different control animals and rats receiving glycerol when studied 18-20 h after glycerol. Following acute volume expansion, however, glycerol-treated rats demonstrated significantly higher pressures than control rats. On the other hand, proximal tubular pressures were comparable in glycerol-treated and control animals receiving the chronic volume expansion.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental models of nephrotoxic acute renal failure

Table 1 summarizes the findings in these three models of nephrotoxic acute renal failure. As can be noted, leakage of filtrate across damaged tubular epithelium is a factor in each instance. Some degree of tubular obstruction is probably present in each model but is of major importance only with severe tubular injury. Hemodynamic alterations and a change in the ultrafiltration coefficient may also play a role in the renal functional impairment. It is not presently possible to quantitatively determine the significance of each of these abnormalities in a given experimental model.

Urea reabsorption along the papillary collecting duct in potassium-deficient rats

These experiments were designed to evaluate the hypothesis that K+ deficiency may be associated with decreased delivery of urea to the renal papillary collecting duct and/or decreased reabsorption of urea from the papillary collecting duct. Either of these factors would result in diminished capacity for urea recycling and might explain the mechanism of the urinary concentrating defect that is observed in K+ depletion. Munich-Wistar rats were fed 25 ml of water and 12 g of normal (CON) or K+-deficient (KD) diet each day for 21 days. Papillary collecting duct samples were obtained by micropuncture through the intact ureter. Fractional delivery of H2O to the base and tip of the papillary collecting duct was increased in KD as compared to CON rats (1.50 +/- 0.30% in KD vs 0.72 +/- 0.09% in CON at the base, P less than 0.01; and 0.55 +/- 0.08% in KD vs 0.30 +/- 0.05% in CON at the tip, P less than 0.01). However, fractional delivery of urea to the base and tip of the papillary collecting duct was not different between KD and CON rats (26.9 +/- 5.6% in KD vs 21.4 +/- 3.3% in CON at the base, P greater than 0.05; and 12.4 +/- 1.5% in KD vs 10.4 +/- 1.4% in CON at the tip, P greater than 0.05). Furthermore, reabsorption of water or urea between the base and tip of the papillary collecting duct was not decreased in KD as compared to CON rats (water reabsorption was 57.8 +/- 4.4% in KD and 55.9 +/- 5.11% in CON and urea reabsorption was 45.0 +/- 6.5% in KD and 45.9 +/- 5.4% in CON, P greater than 0.05). These results demonstrate that water reabsorption, but not urea reabsorption, is impaired in renal tubules proximal to the accessible papillary collecting duct in hydropenic rats.

Renal ischemic injury in the dog: characterization and effect of various pharmacologic agents

Renal ischemia has been implicated as a major factor in the pathogenesis of acute renal failure. Despite several differences between the intrarenal norepinephrine infusion and renal artery occlusion models, they have been assumed to be prototypic models of ischemic renal injury. In our previous studies, an intrarenal infusion of norepinephrine caused a marked reduction in inulin clearance 3 hours after infusion. This reduction could be significantly attenuated by the concurrent infusion of mannitol, furosemide, or bradykinin. The effects of these three protective agents were evaluated before and after variable durations of renal artery occlusion to establish the similarities between the models and the magnitude of versatility of these protective agents. In the renal artery occlusion model, capsular fascia was stripped to eliminate collateral flow and ensure maximal renal ischemia. Three hours after 120 minutes of renal artery occlusion (n = 7), inulin clearance returned to 5.7% +/- 2.2% (SEM) of the control values and was not statistically different from that observed in the norepinephrine model. Intrarenal infusion of mannitol, furosemide, or bradykinin prior to and during the occlusion period, however, had no protective effect. Shorter durations of renal artery occlusion were evaluated to ensure an equivalent or decreased severity of acute renal failure compared with the norepinephrine model. After 90 or 60 minutes of renal artery occlusion, the clearance of inulin returned to 10.9% +/- 3.3% (n = 8) and 31.1% +/- 8.2% (n = 4) of control values, respectively. An intrarenal infusion of mannitol, furosemide, or bradykinin still had no significant protective effect, despite the decreased insult in the 60-minute renal artery occlusion studies. In summary, these findings demonstrate fundamental differences between renal artery occlusion and the norepinephrine model of renal functional impairment, and they suggest that the insult associated with norepinephrine infusion may involve factors other than cessation of blood flow.

Ischemic acute renal failure in the rat: protective effect of uninephrectomy

Experiments were performed to investigate the effect 2-wk prior nephrectomy has on the recovery from a 40-min renal artery occlusion. Two groups were initially examined. Group 1 animals underwent sham nephrectomy and group 2 animals right nephrectomy 14 days prior to a 40-min left renal artery clamp. The percent recovery of inulin clearance in group 2 (33 +/- 6%) was not significantly different from that in the group 1 (36 +/- 8%) when measured 3 h after reflow. At 24 and 48 h of reflow, however, group 2 animals had a significantly higher percent recovery of inulin clearance (24 h: 31 +/- 5%; 48 h: 50 +/- 11%) than group 1 animals (24 h: 1 +/- 1%; 48 h: 8 +/- 4%). Similarly the histology was better preserved at 24 and 48 h in group 2. To further investigate this enhanced recovery, three additional groups were studied. Group 3 underwent right nephrectomy at the time of renal artery occlusion. Group 4 had right uretero-venostomies created immediately prior to the ischemic insult, and group 5 had their aortas rather than left renal arteries clamped. Each group shared with group 2, ischemia to all functioning excretory tissue. The percent recovery of inulin clearance in group 3 (48 +/- 9%), group 4 (54 +/- 5%), and group 5 (42 +/- 6%) were each significantly (P less than 0.005) higher than in group 1 (8 +/- 4%) when measured at 48 h. We conclude that the protection offered by uninephrectomy is not a consequence of hypertrophy but that alterations in the environment which follow ischemia to all functioning excretory renal tissue are responsible for the enhanced recovery seen.

Percutaneous transluminal coronary angioplasty of a coronary artery with a total occlusion

Percutaneous transluminal coronary angioplasty has become an accepted therapeutic modality for patients with coronary artery disease. Until the present, its use has been restricted to vessels that are subtotally obstructed. We recently successfully utilized coronary angioplasty in a patient with a totally occluded coronary artery. The experience is described and criteria proposed for the selection of patients with totally obstructed coronary arteries for coronary angioplasty.

Prosthetic heart valves: a review

There are a number of difficulties inherent in the analysis of such a large and diverse quantity of data. In a substantial number of clinical trials, there is no significant effort made to evaluate prosthetic performance as a function of preoperative cardiac anatomy. Hemodynamics have not been systematically studied in relation to preexisting left ventricular size, shape, or configuration, mitral annular orientation, or left atrial size. Postoperative anticoagulation protocols vary from one institution to another and occasionally within study groups themselves. Less tangible variables such as alteration in surgical technique over time and differential familiarity of cardiovascular surgeons with the prostheses employed are chronic problems in any study of this sort. Perhaps the greatest variable in evaluating the postoperative performance of valvular prostheses over the past 20 yr is the radical improvement in techniques of intraoperative myocardial preservation. Notwithstanding, comparisons are possible within the confines of certain criteria. The caged ball value remains in use after 20 years of clinical experience. It has sustained the greatest number of modifications, probably because it has been the most extensively studied. Hemodynamics are adequate although its centrally obstructed design is responsible for increased turbulence, hemolysis, and neointimal proliferation, particularly in the aortic position. The device has been shown to be durable with virtually no reports of ball variance since the alteration of the silicone curing procedure in 1965. Thromboembolic rates are acceptable in the anticoagulated patient while prosthetic thrombosis is not a grave threat in the non-close clearance device. Incidence of endocarditis is not particularly different from that associated with all nonbioprosthetic valves, although there is a much greater published volume of clinical experience concerning recognition and treatment of late prosthetic valve endocarditis in patients with caged ball valves than there is for any other replacement device. Perhaps the most serious disadvantage to caged ball design is its size. Its large spatial requirements have led to anatomic complications in patients with small aortic roots, isolated mitral stenosis, left ventricular hypertrophy, and double valve replacement, among others. Nevertheless, this is still the valve of choice in some centers.(ABSTRACT TRUNCATED AT 400 WORDS)

Host-parasite interactions in the pathogenesis of experimental renal candidiasis

To study the pathogenesis of renal candidiasis, viable Candida albicans blastospores were injected directly into the left renal artery of New Zealand white rabbits. The progression of the disease was followed by light and electron microscopy over a 6-day period. Within 5 minutes after injection of the yeasts, the organisms localized within glomerular and peritubular capillaries of the cortex. Localization of yeasts within the capillaries occurred through adherence, demonstrated by the presence of surface fibrils originating from the yeast cells. Two to 10 hours later, inflammatory nodules comprised of polymorphonuclear leukocytes formed within capillary lumina. Many of the entrapped yeasts remained viable and extended through adjacent endothelium and epithelium by the formation of germ tubes which penetrated between or directly through intact host cells. After 24 hours, numerous hyphal forms were observed within tubules of the cortex, and some necrotic host cells were noted at sites of penetration. Abscesses replaced renal parenchyma in focal areas during subsequent time intervals. These studies indicate that attachment of Candida albicans to endothelium within capillaries of the cortex is a key event in the disease process. Also, growth of germ tubes into renal tubules provides a temporal advantage for amplification of Candida organisms.

Myeloma kidney cast nephropathy in a rat model of multiple myeloma

Renal insufficiency occurs in some, but not all, patients with multiple myeloma and Bence Jones proteinuria. Many of these patients are found to have a distinctive renal lesion characterized by distal nephron cast formation. It has been proposed that the specific Bence Jones protein (BJP) which is produced by a myeloma tumor may play an important role in the genesis of this cast nephropathy and that patients excreting BJPs with the highest isoelectric points (pI) are those most likely to develop this cast nephropathy. We have utilized a rat model of multiple myeloma to further evaluate the relationship between Bence Jones proteinuria and the development of myeloma cast nephropathy. This model employed immunoglobulin-secreting tumors obtained from a unique strain of rats in which they spontaneously develop. These tumors were transplanted to a homologous strain of rats and the effect on renal function and morphology in these rats were evaluated. Four different kappa light chain synthesizing tumors were studied. Following transplantation of the tumors, all rats were maintained on a diet designed to produce an acid urine (pH 5.5 to 6.0) and maximal urinary concentration (2000 to 3000 mOsm/kg). Among the rats excreting BJP of pI 6.7, 17 of 18 had virtually normal renal histology. Of the 15 rats with BJP of pI 7.6, 11 also had normal renal histology. However, 12 of 12 rats excreting BJP of pI 5.2 developed a distal nephron, light chain containing cast nephropathy. In the pI 4.3 group, 6 of 12 rats developed acute tubular necrosis, and the remaining six animals sustained a less severe lesion which was characterized by the presence of bland hyaline casts. The mean serum creatinine level obtained at the time of sacrifice was elevated (compared to that found in sham-operated controls) in the pI 5.2 group (P less than 0.001) and the pI 4.3 group (P less than 0.01) but not in the pI 6.7 or 7.6 groups. These results do not support the concept that cationic BJP's are more nephrotoxic than those that carry a more negative charge and indicate that other factors must determine the nephrotoxicity of a given BJP.

Alterations in vascular function and morphology in acute ischemic renal failure

Left renal arteries of rats were clamped for 40 min, and the kidneys were studied 48 hr and 7 days following restoration of blood flow. At 48 hr, there was severe oliguria or anuria. Renal blood flow (RBF) was in the normal range, but there was a loss of RBF autoregulation between 95 to 120 mm of mercury in seven out of nine rats. Morphologically, arcuate and interlobular arteries and afferent arterioles showed focal, segmental necrosis of smooth muscle cells and diapedesis of red blood cells across their walls. At 7 days, renal function was still severely depressed. RBF showed a slight decrease that did not reach statistical significance, and RBF autoregulatory capacity was lost in 8 out of 11 rats. Morphologically, vascular lesions were characterized at this stage by marked thickening and fibrosis of the tunica adventitia of the interlobular arteries and afferent arterioles. Structural vascular alterations may impair smooth muscle contractile function and thus interfere with RBF autoregulatory function in this model of acute renal failure.

Glomerular dynamics

The kidney glomerulus produces an essentially protein-free filtrate of blood that is converted to urine as it traverses the remainder of the nephron. Recent studies, largely carried out in animals, have provided new information on the determinants of glomerular function. These findings, briefly summarized herein, are also related to clinical conditions.