Low Serum Neutrophil Gelatinase-associated Lipocalin Level as a Marker of Malnutrition in Maintenance Hemodialysis Patients

Background

Neutrophil gelatinase-associated lipocalin (NGAL or LCN2) is an iron-transporting factor which possesses various activities such as amelioration of kidney injury and host defense against pathogens. Its circulating concentrations are elevated in acute and chronic kidney diseases and show a positive correlation with poor renal outcome and mortality, but its clinical significance in maintenance hemodialysis (HD) patients remains elusive.

Methods

Serum NGAL levels were determined by enzyme-linked immunosorbent assay in out-patient, Japanese HD subjects. Their correlation to laboratory findings and morbidity (as development of severe infection or serum albumin reduction) was investigated using linear regression analysis and χ² test.

Results

Pre-dialysis serum NGAL levels in HD patients were elevated by 13-fold compared to healthy subjects (n=8, P<0.001). In a cross-sectional study of 139 cases, serum NGAL concentrations were determined independently by % creatinine generation rate (an indicator of muscle mass, standardized coefficient β=0.40, P<0.001), peripheral blood neutrophil count (β=0.38, P<0.001) and anion gap (which likely reflects dietary protein intake, β=0.16, P<0.05). Iron administration to anemic HD patients caused marked elevation of peripheral blood hemoglobin, serum ferritin and iron-regulatory hormone hepcidin-25 levels, but NGAL levels were not affected. In a prospective study of 87 cases, increase in serum albumin levels a year later was positively associated to baseline NGAL levels by univariate analysis (r=0.36, P<0.01). Furthermore, within a year, patients with the lowest NGAL tertile showed significantly increased risk for marked decline in serum albumin levels (≥0.4 g/dl; odds ratio 5.5, 95% confidence interval 1.5–20.3, P<0.05) and tendency of increased occurrence of severe infection requiring admission (odds ratio 3.1, not significant) compared to the middle and highest tertiles.

Conclusion

Low serum NGAL levels appear to be associated with current malnutrition and also its progressive worsening in maintenance HD patients.

The prevention of ischemia/reperfusion induced oxidative damage by venous blood in rabbit kidneys monitored with biochemical, histopatological and immunohistochemical analysis

The purpose of this study was to investigate the biochemical, histopathological and immunohistochemical effects of venous blood on ischemia/reperfusion-induced oxidative DNA damage and mutation in rabbit kidneys in comparison to melatonin treatment, which has a known protective effect against ischemia/reperfusion (IR) injury. The rabbits were divided into five groups: renal ischemia (RI), renal ischemia-reperfusion (RIR), renal ischemia-venous blood-reperfusion (RIVR), melatonin + renal ischemia-reperfusion (MRIR), and the healthy sham control group (HG). Melatonin (2.5 mg/kg delivered intraperitoneally) was administered one hour prior to ischemia. In the RIVR group, 1 ml of venous blood was administered 5 minutes before the reperfusion. The xanthine oxidase activity in the kidney tissue was determined as 53.50 ± 1.72, 31.00 ± 6.39, 45.66 ± 9.20, 28.66 ± 6.05 and 14.33 ± 1.28 U/g protein; the MDA levels were 6.32 ± 0.02, 19.50 ± 1.33, 7.00 ± 0.96, 7.50 ± 0.76 and 4.75 ± 0.34 mmol/g protein; and the GSH levels were 4.50 ± 1.08, 2.76 ± 0.13, 5.48 ± 0.22, 4.93 ± 0.55 and 6.98 ± 0.33 nmol/g protein in the RI, RIR, RIVR, MRIR and HG groups, respectively. Blood, blood urea nitrogen (BUN) and creatinine levels were classified as high only in the RIR group. The MRIR and RIVR groups, in which oxidative stress was best suppressed, had much milder histopathological and immunohistochemical findings compared to the RIR group. This study has revealed that it is useful to initiate reperfusion of the ischemic tissue with venous blood.

Plasma Renin in ipsilateral renal vein in patients with chronic unilateral pelvic ureteric junction obstruction

Acute experimental hydronephrosis induces increased output of renin from ipsilateral kidney. In most clinical presentation of unilateral hydronephrosis the patients are however, normotensive with normal circulating plasma renin activity. In consideration of this argument we undertook this prospective study of ipsilateral renal vein renin activity in children with congenital Pelvic Ureteric Junction Obstruction (PUJO) and compared with other wise normal children. In this prospective cross-sectional study, started from July 99 to June 2001, twenty patients, age upto 12 years, with unilateral hydronephrosis and in control group ten patients without hydronephrosis were taken. 2ml blood was taken from the renal vein in study group and from infrarenal portion of inferior vena cava during exploratory laparotomy from the control group. All the patients had advanced grade of hydronephrosis and two patients (13%) had mild hypertension. In this study the mean plasma renin activity (PRA) was 45.58 ng/ml/hr (range: 11.69-67.56 ng/ml/hr) in study group. The mean PRA in control group was 5.9ng/ml/hr. The result of study group was significantly higher than normal (P value 0.0003). In Bangladesh we are doing more conservative kidney preserving surgery for PUJO, but need long term follow up of the patients undergoing surgery for PUJO in childhood for potential of developing renin-angiotensin induced hypertension in later life.

Changes in cytokine concentrations in graft renal vein during reperfusion in patients with and without delayed graft function

INTRODUCTION

The impairment of organ function derived from ischemia-reperfusion injury is still an important problem in solid organ transplantation. Cell alterations induced by ischemia prime the tissue for the subsequent damage that occurs during the reperfusion phase. Despite recent advances in immunosuppressive therapy, delayed graft function (DGF) remains an important problem after kidney transplantation. Different studies have related various clinical factors to DGF, such as donor age, recipient age, cold ischemia time, initial immunosuppressive regimens. The aim of present study was to examine the changes in cytokine concentrations in graft renal vein during the reperfusion in relation to the development of delayed graft function.

MATERIAL AND METHODS

The study included 17 recipients of cadaveric renal grafts (10 males, 7 females, mean age 49 +/- 7 years, cold ischemia time 25 +/- 3 h)--8 with DGF and 9 without DGF. Levels of IL-lbeta, IL-2, IL-4, IL-6, IL-8, IL-10, IFN-gamma, TNF-beta and TNF-alpha in renal graft vein plasma during 5 first min. of reperfusion were quantified by flow-cytometry.

RESULTS

The increased concentrations ofIL-6, TNF-alpha and IL-1beta were observed during reperfusion. However there were no statistically significant differences between patients with and without DGF.

[Changes of renal vein renin activity in patients with unilateral atherosclerotic renal artery stenosis]

OBJECTIVE

To assess plasma renin activity (PRA) of renal veins in patients with unilateral renal artery atherosclerotic stenosis and its relationship with blood pressure changes after renal artery stenting.

METHODS

Fifty patients with significantly unilateral renal artery stenosis (lumen loss > or = 70%) and coronary artery stenosis were included. Bilateral renal vein and peripheral PRA and angiotensin II were determined and their relations with blood pressure changes after stenting were analyzed.

RESULTS

All patients were revascularized successfully for both coronary and renal artery stenosis. PRA in the ischemic kidney was significantly higher than that in the contralateral kidney (1.44 +/- 1.73 ng.ml(-1).h(-1) vs 1.27 +/- 1.57 ng.ml(-1).h(-1), P = 0.04). Ischemic and contralateral renal vein renin ratio (RVRR) was > or = 1.5 in 14 patients (28%) (renal vascular hypertension, RVH group). During follow-up (12 +/- 9 months), blood pressure returned to normal in 9 patients after revascularization, 7 were of RVH group (50%) and 2 were in control group (6%) (P < 0.001). Multivariate logistic analysis indicated RVRR > or = 1.5 was significantly related to the decrease of hypertension after renal artery stenting (OR = 3.15, 95% CI = 1.49 approximately 5.97, P = 0.02).

CONCLUSIONS

PRA was significantly increased in the ischemic kidney in about one-third of patients with unilateral renal artery stenosis. Hypertension could be controlled easily to normal value after renal artery stenting in half of the patients with RVRR > or = 1.5. Measurement of renal vein renin activity in patients with renal artery stenosis is very useful in evaluating the effects of renal artery stenting on hypertension.

Glucuronidation of 1-naphthol and excretion into the vein in perfused rat kidney

UDP-glucuronosyltransferase is expressed in the proximal convoluted tubular cells of rat kidney. Kidney perfusion with a Krebs-Henseleit buffer containing 1-naphthol was performed to estimate the dynamics and disposition of the glucuronide conjugate formed in the epithelial cells of the renal tubules. When 1-naphthol was injected into the renal artery, and the perfusate from the renal vein was returned to a reservoir and recirculated through the kidney preparation (recirculating perfusion), most of the 1-napthol was immediately excreted into the vein as a glucuronide conjugate and its concentration increased rapidly. In contrast, the 1-napthol glucuronide appeared more slowly in the urine. 1-Naphthol was also injected during the initial 5 min of perfusion under single-pass perfusion conditions (single-pass perfusion) in situ, and the metabolite and parent compound in the venous perfusate and in urine were assayed. Under this condition, most of the 1-naphthol glucuronide was excreted into the renal vein, and not urine. Phenol UDP-glucuronosyltransferase was highly induced in the rat kidney by beta-naphthoflavone treatment. Moreover, the amount of 1-naphthol glucuronide excreted in the renal vein was increased 2.7-fold in the perfused kidney of beta-naphthoflavone-treated rats, but the amount in the urine was not significantly increased under singlepass perfusion conditions. These results indicate that the kidney can glucuronidate phenolic xenobiotics in epithelial cells of the tubules and excrete the resultant glucuronide into the renal vein.

Kidney-targeted naked DNA transfer by retrograde injection into the renal vein in mice

We recently developed a novel kidney-targeted gene transfer technique in rats, using the retrograde renal vein injection of naked plasmid DNA. Many animal disease models are created in mice by transgenic or knockout technologies. However, it is much harder to perform renal vein injection in mice than in rats because they have a thin and short vein. Here we transferred the mouse interleukin (IL)-10 gene into mice by retrograde renal vein injection, using an IL-10 and immunoglobulin fusion protein (IL-10/Fc) (96-kDa) expression plasmid, pCAGGS-IL10/Fc. We observed a dose-response relationship between serum IL-10 levels and the amount of injected DNA. The serum IL-10 levels peaked at day 1 and then were sustained for at least 2 weeks. These results demonstrate that the kidney-targeted naked plasmid DNA transfer of mice by retrograde renal vein injection can be achieved, and the kidney serves as a depot organ for the production of large proteins.

Hypertension and renovascular disease: follow-up on 100 renal vein renin samplings

The clinical value of renal vein renin sampling (RVRS) as a prognostic tool in the treatment of renovascular hypertension was evaluated. One hundred consecutive patients were included over a 4-year period of time. About half of the patients (49%) were treated interventionally by PTRA (21%), nephrectomy (20%), or vascular surgery (8%). Seven patients (15%) were cured and 15 (32%) had improved (reduction in antihypertensive medicine) after 6 months follow-up, whereas three patients (6%) were cured and 12 (26%) improved after 3-4 years follow-up. Thus, the number of patients cured or improved is comparable with the results from our department reported 20 years ago. However, in the present report, more than twice as many patients were enrolled, leading to double costs. Different indices of lateralisation of the renin generation were calculated for the use in cases of a shrunken kidney (functional share < or =15%). None of the indices clearly discriminated between the patients who did benefit from intervention, and those who did not. The only positive finding was that a peripheral renin concentration lower than 8 mlU/l predicted no effect of intervention, which might lead to the exclusion of 11% of the patients before entering the diagnostic programme. We conclude that the RVRS demands a very restrictive referral pattern if it should be of prognostic value for the blood pressure outcome after intervention. No indices of lateralised renin concentrations proved high predictive value. However, a peripheral renin concentration low in the normal range seems useful as an indicator of no benefit from intervention.

Vasculogenesis and angiogenesis in the subcardinal venous plexus of quail mesonephros: spatial and temporal morphological analysis

Vasculogenesis and angiogenesis are involved in a coordinated program for the development of the mesonephric subcardinal venous plexus of quail embryo. Vasculogenesis occurs between days 3 and 4 of incubation, while angiogenesis takes place from day 5 to day 7. Examination of vascular corrosion casts and whole mounts, and tissue sections labelled with specific markers to hemangioblast lineage (QH1, LEP100 and AcPase activity), allowed us to distinguish six phases in the formation of subcardinal plexus. (1) Appearance of isolated angioblast-like cells where the subcardinal plexus will form. (2) Alignment of angioblast-like cells into cellular strands. (3) Formation of compact vascular cords by association of angioblast-like strands. (4) Polygonal interconnection of vascular cords to constitute the primary subcardinal plexus. In this stage, isolated angioblast-like cells were present inside inter-vascular spaces. (5) The splitting of primary inter-vascular spaces by angiogenic sprouts to form secondary subcardinal plexus (outward angiogenesis). Isolated angioblast-like cells were not present in this stage. (6) Expansion of the secondary subcardinal plexus by insertion of slender transcapillary tissue pillars (inward angiogenesis) and angiogenic sprouts. We also describe three morphogenetic gradients during the development of the subcardinal plexus: ventral-to-dorsal, cranial-to-caudal and lateral-to-medial.

Antioxidants block angiotensin II-induced increases in blood pressure and endothelin

Chronically infusing a subpressor dose of angiotensin (Ang) II increases blood pressure via poorly defined mechanisms. We found that this hypertensive response is accompanied by increased oxidant stress and is prevented by blocking endothelin (ET) receptors. Thus, we now tested whether blocking oxidant stress decreases both blood pressure and ET levels. We infused Sprague-Dawley rats (via osmotic pumps) with either vehicle (group 1) or Ang II (5 ng. kg(-1). min(-1); groups 2 to 4) for 15 days. Groups 3 and 4 also received either tempol in the drinking water (1 mmol/L) or vitamin E (5000 IU/kg diet), respectively, for 15 days. We measured systolic blood pressure (SBP) and urinary nitrite excretion every 3 days, and on day 15 we measured systemic and renal venous plasma levels of ET, isoprostanes, and thiobarbituric acid reactive substances (TBARS). SBP in Group 1 did not change throughout the study, whereas Ang II increased SBP (from 132+/-5 to 151+/-7 mm Hg). In addition, Ang II increased the systemic and renal venous levels of isoprostanes, TBARS, and ET and caused a transient decrease in urinary nitrites (that returned to control levels by day 9). Both tempol and vitamin E prevented Ang II-induced hypertension and either prevented or tended to blunt the increase in systemic and renal isoprostanes, TBARS, and ET. Finally, both antioxidants abolished the transient decrease in urinary nitrites. These results together with our previous study suggest that subpressor-dose Ang II increases oxidant stress (and isoprostanes). This in turn increases ET levels, which participate in the hypertensive response to Ang II.

The return of glomerular filtered albumin to the rat renal vein--the albumin retrieval pathway

BACKGROUND

Recent studies have demonstrated that the normal glomerular capillary wall (GCW) is not charge selective to albumin. This means that albumin flux across the GCW is high. This has been confirmed in studies where albumin uptake by the tubules has been inhibited. Therefore, there must be a high capacity postglomerular retrieval pathway in normal kidneys that returns filtered albumin back to the blood supply.

METHODS

This study identifies the presence of glomerular filtered albumin in the renal vein from the analysis of the decrease of radioactivity in the venous effluent after the injection of a pulse of tritium labeled albumin into the renal artery in vivo and in the isolated perfused kidney (IPK).

RESULTS

The glomerular filtered albumin is returned to the blood supply by a high capacity pathway that transports this albumin at a rate of 1830+/-292 microg/min rat kidney (n= 14) (mean+/-SEM). This pathway has been identified under physiological conditions in vivo and in the IPK. The pathway is specific for albumin as it does not occur for horseradish peroxidase (HRP). The pathway is inhibited in a non-filtering kidney. The pathway is also inhibited by NH4Cl, an inhibitor of protein uptake.

CONCLUSIONS

The high capacity retrieval pathway for albumin is most likely associated with transtubular cell transport. It is also apparent that most albuminuric states could be accounted for by the malfunctioning of this pathway without resorting to any change in glomerular permselectivity.

The return of glomerular-filtered albumin to the rat renal vein

BACKGROUND

Recent studies have demonstrated that the normal glomerular capillary wall (GCW) is not charge selective to albumin. This means that albumin flux across the GCW is high, and this has been confirmed in studies in which albumin uptake by the tubules has been inhibited. Therefore, there must be a high-capacity postglomerular retrieval pathway in normal kidneys that returns filtered albumin back to the blood supply.

METHODS

This study identifies the presence of glomerular-filtered albumin in the renal vein from the analysis of the decrease of radioactivity in the venous effluent after the injection of a pulse of tritium-labeled albumin into the renal artery in vivo and in the isolated perfused kidney.

RESULTS

The postglomerular filtered albumin is returned to the blood supply by a high-capacity pathway that transports this albumin at a rate of 1830 +/- 292 micrograms/min.rat kidney (N = 14, mean +/- SEM). This pathway has been identified under physiological conditions in vivo and in the isolated perfused kidney. The pathway is specific for albumin, as it does not occur for horseradish peroxidase. The pathway is inhibited in a nonfiltering kidney. The pathway is also inhibited by ammonium chloride (an agent that inhibits tubular protein uptake but does not alter glomerular size selectivity) and by albumin peptides (which compete for the tubular albumin receptor).

CONCLUSIONS

The high-capacity retrieval pathway for albumin is most likely associated with transtubular cell transport. It is also apparent that most albuminuric states could be accounted for by the malfunctioning of this pathway without resorting to any change in glomerular permselectivity.

Metabolism of cAMP to adenosine in the renal vasculature

We recently demonstrated that cAMP added to the perfusate increased the renal venous recovery of adenosine in the isolated rat kidney, an effect blocked by inhibition of ecto-phosphodiesterase and ecto-5'-nucleotidase. Although our previous study established the cAMP-adenosine pathway, i.e., the conversion of cAMP to adenosine, as a viable metabolic pathway within the kidney, that study did not determine whether conversion of arterial cAMP to adenosine recoverable in the venous effluent occurred in the tubules versus nontubular sites. In the current study, we addressed this issue by determining the effects of blocking cAMP transport into the renal tubules with probenecid (0.1, 0.3 and 1 mM) on the increase in renal venous output of adenosine induced by adding cAMP (30 microM) to the perfusate of isolated rat kidneys. Addition of cAMP to the perfusate caused a marked increase in renal venous secretion of adenosine, an effect that was augmented, rather than inhibited, by probenecid. To test the hypothesis that the renal vasculature supports a cAMP-adenosine pathway, cultured rat preglomerular vascular smooth muscle cells were incubated with cAMP (30 microM) for 1 hr in the presence and absence of 3-isobutyl-1-methylxanthine (a phosphodiesterase inhibitor). Incubation with cAMP increased extracellular adenosine levels 41-fold, and this effect was abolished by 3-isobutyl-1-methylxanthine. In a third experimental series, addition of cAMP (0.3, 1, 3, 10 and 30 microM) to the perfusate of isolated rat kidneys and mesenteric vascular beds increased the renal venous, but not mesenteric venous, output of AMP, adenosine and inosine. We conclude that the renal vasculature supports a cAMP-adenosine pathway, that administering cAMP into the renal artery and measuring adenosine in the venous effluent of the perfused rat kidney most likely monitors primarily the renal vascular cAMP-adenosine pathway and that the quantitative importance of the cAMP-adenosine pathway is not equivalent in all vascular compartments.

Renal clearance of atrial natriuretic peptide during acute unilateral complete ureteral obstruction in the pig

Renal extraction and renal plasma clearance of atrial natriuretic peptide from pigs with complete unilateral ureteral obstruction (UUO) and from intact anaesthetized pigs were determined from arteriovenous differences in plasma atrial natriuretic peptide and measured renal plasma flow. The effect of administration of either a cyclooxygenase inhibitor or an angiotensin converting enzyme inhibitor was examined during UUO. Renal extraction ratio and renal clearance rate of plasma atrial natriuretic peptide (ANP) in the intact pig was stable during the 15 h observation period. UUO resulted in a significant (P < 0.05) temporary increase in renal extraction ratio and a significant (P < 0.05) reduction in the renal clearance rate of atrial natriuretic peptide. During cyclooxygenase inhibition there was a significant increase in the renal extraction ratio of ANP. During angiotensin II converting enzyme inhibition, renal handling of atrial natriuretic peptide did not differ from that observed in control animals. The present data demonstrate that atrial natriuretic peptide is extracted by the obstructed kidney. Despite the significant reduction in renal blood flow during indomethacin administration, renal clearance of ANP was unaltered. The increase in ipsilateral renal extraction of atrial natriuretic peptide immediately after ureteral obstruction and indomethacin administration could be explained either by a direct influence of PGE2 on the renal haemodynamics altering renal extraction of ANP, or by a compensatory mechanism attempting to preserve renal function.

A renin-secreting tumour with severe hypertension and cardiovascular disease: a diagnostic and therapeutic challenge

A case of renin-secreting juxtaglomerular cell tumour which presented with a severe hypertensive crisis and did not respond to angiotensin converting enzyme inhibitors but was promptly controlled by intravenous labetalol is reported. The diagnostic difficulties which can be encountered in such cases and the usefulness of the different diagnostic tests, including renal vein renin measurement, are discussed.

Changes in renal vein, renal surface, and urine oxygen tension during hypoxia in pigs

To determine whether ureteral urine oxygen tension could serve as a monitor of renal hypoxia and its relationship to other renal O2 tension parameters, we simultaneously measured femoral artery (PaO2), renal vein (PrvO2), renal surface (PrsO2), and ureteral urine (PuO2) oxygen tensions in 8 anesthetized pigs while incrementally decreasing the inspired oxygen concentration (FiO2) from 21% to 12%. Renal artery blood flow, measured by transit time ultrasound, renal oxygen consumption, and thermodilution cardiac output, was constant. Changes in PaO2, PrvO2, PrsO2, and PuO2 caused by decreasing FiO2 were evaluated by one-way analysis of variance. The relationships between PuO2 and the other O2 tension parameters were evaluated by correlation coefficient and linear regression statistics. Of six possible O2 decrements (combinations of 3, 6, and 9%), only PrvO2 significantly decreased with all six decrements. PuO2 decreased when FiO2 decreased 6% or more. PuO2 is not a sensitive indicator of systemic hypoxia. Under constant renal perfusion and oxygen consumption, PuO2 had a correlation coefficient of 0.80 and a regression equation of PuO2 = 0.84 (PrvO2) + 11.6, with PrvO2. PuO2 is related to PrvO2 when renal perfusion is constant.

Decrease in cyclosporin-mediated prostacyclin production in renal versus carotid arteries: a mechanism for cyclosporin-induced hypertension

Although the mechanism of cyclosporin (CsA)-induced hypertension is unknown, it has been shown to inhibit prostacyclin (PGI2) production directly, which may be a factor. We determined whether CsA had a differential effect on PGI2 production from the carotid artery (CA) and internal jugular vein (JV) compared to that from the renal artery (RA) and vein (RV) as a possible contributing factor to renovascular hypertension based upon the ability of organs to regulate their own blood flow according to local circumstances. The neck and renal vessels were removed from anesthetized adult female dogs (N = 8) and placed in a stimulation chamber, with Cell I being control (Hepes buffer), Cell II containing 0.3 mg/ml CsA, and Cell III containing CsA and 25 microM arachidonic acid (AA). Following serial stimulation periods, the supernatant was evaluated for PGI2 production by radioimmunoassay. PGI2 production from CA was significantly higher than that from RA following control and AA stimulation, 1474 +/- 382 pg/cm2-min vs 733 +/- 173 pg/cm2-min (P less than 0.05) and 2236 +/- 347 vs 1090 +/- 217 (P less than 0.01), respectively. CsA-induced PGI2 production from the carotid arteries was significantly greater than that from the renal arteries, 2944 +/- 586 vs 1003 +/- 235 (P less than 0.005). However, stimulation with AA following CsA resulted in sustained PGI2 production in both arteries that was similar to stimulation with CsA alone, 3014 +/- 600 vs 2944 +/- 586 for the carotids and 1278 +/- 280 vs 1003 +/- 235 for the renal arteries.(ABSTRACT TRUNCATED AT 250 WORDS)

Decreased renal preglomerular microvascular PGI2 and PGE2 biosynthesis in cholesterol-fed rabbits

Although atherosclerosis is a common disease afflicting the kidney, few studies have examined the biochemical disturbances associated with this process directly in the renal microvasculature. Using a technique developed in this laboratory to isolate renal preglomerular microvessels, we have examined whether these vascular segments have a reduced capacity to synthesize vasodilator prostanoids (i.e., PGI2 and PGE2), an observation which has been made in atherosclerotic blood vessels from other vascular beds. The synthesis of these two prostanoids was assessed by radioimmunoassay in a group of white New Zealand rabbits fed a 2% cholesterol diet for 30 days and the results compared to that obtained in a similar group of rabbits fed a normal diet. The results of these studies showed the development of hypercholesterolemia in the cholesterol-fed rabbits which was associated with a 35% decrease in the biosynthesis of PGI2 and a 51% decrease in PGE2 in freshly isolated renal preglomerular microvessels. These findings are similar to those observed in non-renal major blood vessels and suggest that common biochemical mechanisms may operate in the development of atherosclerosis in many organ systems.

Tubulovenous communication in myeloma kidney. Tubular prolapse and tubular transformation of renal vein

We studied renal histopathologic findings of 20 autopsy cases with multiple myeloma with particular attention to structural tubulovenous relationship. Urinary deposition in renal vein or lymphatics, which has been previously noted in pyelonephritis, obstructive uropathy, or vesicoureteral reflux was found in 14 cases. Four of 14 cases had unique tubulovenous communications designated as tubular prolase and tubular transformation of vein. Such communications were most frequently seen at the architectural weak point where the thin-walled interlobar vein and their tributaries adjoin the renal pyramid. Simultaneously, Tamm-Horsfall protein used as a marker for the location of urine was detected in renal vein. These changes had no significant correlation to morphologic severity of myeloma kidney or clinical manifestations of renal failure. Thus, tubulovenous communication producing backflow of urine into the circulation is frequently observed among myeloma kidney as well as other tubulointerstitial nephritis, but its clinical significance is unclear.

Age-related changes of noradrenergic innervation of rat splanchnic blood vessels: a histofluorescence and neurochemical study

The influence of ageing on the noradrenergic innervation of superior mesenteric artery and vein, renal artery and vein, and portal vein was studied in male Wistar rats by means of catecholamine histofluorescence, image analysis techniques and high pressure chromatography with electrochemical detection. Old age was accompanied by a marked increase in the density of noradrenergic innervation and an increase of noradrenaline levels in superior mesenteric artery, renal artery, and portal vein. In contrast, no significant age-related changes were observed in the density of noradrenergic innervation or in noradrenaline levels in superior mesenteric and renal vein. The present data indicate that, at least in superior mesenteric and renal artery and portal vein, senescence is not accompanied by loss or by lack of change in the noradrenergic innervation as commonly believed to be the case in many vascular trees. On the basis of our findings it cannot be excluded that increased plasma catecholamine levels observed in senescence derive, in part, from perivascular sympathetic endings.

Kidney, lower limb and whole-body uptake and release of catecholamines in alcoholic liver disease

Regional (kidney, lower limb) and whole-body kinetics of endogenous noradrenaline (NA) and tritium-labelled L-noradrenaline (3H-NA) were determined in patients with alcoholic liver disease (one alcoholic hepatitis, 12 cirrhosis) and in control subjects (n = 6) in order to get information on the sympatho-adrenal system in liver disease. Arterial NA was significantly elevated in ascitic patients (median 2.5 nmol/l, n = 9, P less than 0.05) as compared to non-ascitic patients (1.6 nmol/l) and controls (1.7) nmol/l). NA spillover per unit NA inflow was increased in the kidney in patients with ascites (0.69 vs. 0.45 pmol/min.g per pmol/min.g in controls, P less than 0.005) but not in the lower limb (0.23 vs. 0.49 in controls, P less than 0.01). In patients with ascites the spillover rate of NA from the kidney into plasma (1.9 pmol/min.g) was significantly increased (P less than 0.02) compared to controls and non-ascitic patients (1.2 and 1.0 pmol/min.g, respectively. Patients and control kidneys and limbs extracted almost the same fraction of 3H-NA (0.34 vs. 0.32 NS and 0.34 vs. 0.37 NS, respectively). Whole-body clearance of 3H-NA was not significantly different in cirrhotics and controls (median 0.89 vs. 0.91 l/min.m2), indicating that the raised NA in decompensated cirrhosis reflects enhanced sympatho-adrenal activity rather than decreased metabolism of this amine. Our results do not point towards a uniform sympatho-adrenal overactivity in decompensated cirrhosis, but rather indicate regional differences with different order of NA spillover. The renal sympathetic overactivity, as indicated by the increased renal NA overflow, is likely to be important to the decreased renal perfusion and increased salt-water retention characteristic of this clinical condition.

Autoradiographic localization and characterization of substance P binding in dog kidney

The autoradiographic localization of [125I]Bolton-Hunter substance P (BHSP) was examined in slide-mounted sections of dog kidney and dog renal artery and vein. Biochemical characterization of the binding in sections of dog kidney, demonstrated that BHSP binds to a population of non-interacting sites with high affinity (KD = 0.11 +/- 0.02 nM, Bmax = 0.29 +/- 0.05 fmol/section). The binding was displaced by tachykinins in the order SP greater than NKA much greater than NKB, indicative of binding to NK-1 receptors. BHSP binding to dog kidney was localized over glomeruli and endothelium of intrarenal arteries. There was binding associated with the endothelium and adventitia of the renal artery but not the vein. Binding of BHSP to arcuate arteries and to the renal artery was dependent on the presence of an intact endothelium. No evidence was obtained for receptors associated with any renal tubules. These results suggest that in the dog, vasodilation, diuresis and natriuresis in response to SP may result from an action primarily on the vascular elements of the kidney.

Simple renal cyst and hypertension: cause or coincidence?

Hypertension and simple renal cysts are frequent clinical diagnoses. With the widespread use of new non-invasive diagnostic technics such as abdominal ultrasound and computer-assisted tomography renal cysts are diagnosed with increasing frequency. In patients 50 years or older renal cysts of various size may be found in nearly one third. Similarly, the incidence of hypertension increases with age. Thus, the coexistence of a simple renal cyst and hypertension in a patient may represent a pure coincidence or be a cause of high blood pressure. The effect of cyst removal upon hypertension has been documented in 22 patients in the literature. Surgical cyst removal or percutaneous cyst aspiration caused a significant fall in blood pressure in most patients. The drop in blood pressure was closely related to an activation of the renin angiotensin system in the involved kidney. Fifteen patients (68%) were considered cured and 2 improved after the intervention. All patients had large cysts. It is suggested that in patients with large renal cysts the lesion may, through local tissue and/or renal arterial compression, cause ischemia and in turn activate the renin angiotensin system. Since most of the renal cysts are 2 cm or less in diameter this may represent a very rare event. In patients with large renal cysts and hypertension percutaneous needle aspiration of the cyst and/or renal venous renin determination may be useful tools to determine a causal rather than a coincidental relation between the 2 lesions.

Comparison of renal vein renin activity in hypertensive patients with stenosis of one or both renal arteries

Renal vein renin measurements were compared in 64 hypertensive patients with arteriographically documented stenoses or complete occlusion of one or both renal arteries. The characteristic pattern of curable renovascular hypertension, i.e. increased increment of renin from the ischaemic kidney with contralateral suppression of renin secretion, was seen not only in patients with unilateral stenoses, but also in most patients with bilateral stenoses. Contralateral suppression was less marked in azotemic patients. The highest increments of renal vein renin were seen when the renal artery was completely occluded. The patterns were similar following acute or chronic administration of captopril, suggesting that angiotensin II is not responsible. Increased sodium delivery to the macula densa is postulated as a possible cause of contralateral suppression.

Renal vein renin sampling in essential hypertension using hydralazine and the tourniquet test

The results of renal vein renin sampling were assessed in 40 patients who had uncomplicated essential hypertension. All had normal creatinine clearance, intravenous pyelography, and arteriography. During sampling, renin release was stimulated in 29 patients with intravenous hydralazine and in 11 with the tourniquet blood trapping test. Simultaneous sequential renal vein samples were drawn over a 30-minute period. Positive renal vein renin ratios (greater than or equal to 1.5) were seen in 52% of the hydralazine group at 0 minutes and in 69% post-hydralazine. In the tourniquet group, 27% had a positive ratio at 0 minutes as compared with 64% post-tourniquets. A significant difference was found in renal vein plasma renin activity between the two kidneys (p greater than or equal to .0001). The asymmetry of renal vein renin activity and the large renal vein renin ratios in these two groups suggest the presence of true differences in renin secretion. These differences may be due to focal nephrosclerosis. The therapeutic significance of a positive renal vein renin ratio in the hypertensive patient should be determined in conjunction with arteriography.

Countercurrent diffusion in the renal cortex of the rabbit

Evidence was obtained for countercurrent diffusion of 14C-n-butanol in the rabbit renal cortex. After injection into the renal artery of perfused, isolated rabbit kidneys, concentrations of both 14C-butanol and tritiated water in the initial samples collected from the renal venous outflow exceeded those of 125I-albumin when the rate of perfusion was low. When flow was increased, the 125I-albumin curve was shifted to earlier times relative to the other labels. These observations confirm the existence of arteriovenous diffusion of 14C-butanol and tritiated water in the kidney. In a second set of experiments, 14C-butanol and tritiated water were infused for 10 or 60 seconds into the renal arteries of anesthetized rabbits, and the kidneys were then removed and frozen in liquid nitrogen. Cores were cut from the kidney surface and sectioned in a cryostat, and the ratio of 14C-butanol to tritiated water was calculated at increasing depths in the cortex. This ratio rose from 0.54 +/- 0.03 (SEM) at the surface to 0.98 +/- 0.07 at 3 mm beneath the surface in kidneys perfused for 10 seconds. This gradient was less steep after 60 seconds of perfusion. The early appearance of 14C-butanol relative to tritiated water in the renal venous outflow and delayed equilibration of 14C-butanol in the outer renal cortical tissue are consistent with counter-current diffusion. It is suggested that this exchange may occur between adjoining interlobular arteries and veins in the cortex and may contribute to high carbon dioxide tensions found near the renal surface.

Predictive value and changes of renin secretion in hypertensive patients with unilateral renovascular disease undergoing successful renal angioplasty

Peripheral and renal vein renin activity was measured in 46 hypertensive patients with arteriographically diagnosed unilateral renal artery stenosis before and six months after technically successful renal angioplasty. The renin-sodium profile was high in 80 percent before angioplasty, fell in all patients, and became normal or low in 85 percent after angioplasty. Renal vein renin activity, which initially showed lateralization of renin secretion to the ischemic kidney with contralateral suppression, became normal. Renal vein renin activity was more reliable for predicting the therapeutic response when expressed as the increment of renin for each renal vein over the infrarenal vena caval value (sensitivity 74 percent, specificity 100 percent) than as the ratio between the two renal veins (sensitivity 62 percent, specificity 60 percent). The predictive value of renal vein renin activity is poor when plasma renin activity is stimulated by long-term administration of captopril. These data support the usefulness and define the limitations of peripheral and renal vein renin measurements in selecting patients for treatment by renal angioplasty.

Ultrastructural evidence for a reabsorptive role by intrarenal veins

Intrarenal veins, although known to have thin walls, are considered to be simple conducting vessels. Using light- and electron microscopy, the distribution and structure of named intrarenal veins was examined qualitatively and quantitatively in rat kidneys fixed by retrograde arterial perfusion. Although the venous system follows the pattern of arterial branching in general, a class of intracortical veins similar in appearance to interlobular veins but without a companion artery was found in the present study. It is suggested that these vessels be designated intralobular veins. Structurally, we have found intrarenal veins to be surprisingly similar to peritubular capillaries both in respect to their spatial relations to renal tubules as well as ultrastructurally. Like peritubular capillaries, the majority of the wall of intrarenal veins is intimately apposed to renal tubules. This fraction decreases centrally, values of 0.83 being obtained in intralobular veins, 0.69 in interlobular veins, and 0.56 in arcuate veins. The walls of intrarenal veins are comprised of little more than an endothelium, which, like peritubular capillaries, is remarkable for its thinness, high density of fenestrae, and lack of extraintimal elements. Endothelial thickness was not significantly greater in either interlobular or arcuate veins than in peritubular capillaries; the fenestrae were, however, about twice as frequent in peritubular capillaries as in interlobular or arcuate veins and 35 times more frequent than in interlobar veins. The size and numerical and volume densities of uncoated endocytotic vesicles did not differ significantly between peritubular capillaries and any of the intrarenal veins. Based on their marked qualitative and quantitative similarities to peritubular capillaries, we conclude that, like the latter, intrarenal veins are capable of sustaining passive transport between plasma and interstitium.

Avian renal portal valve: a reexamination of its innervation

The renal portal circulation of the avian kidney contains a unique smooth muscle valve that can direct blood flow from the posterior extremities to the central circulation or through the kidney. The neural control of the valve and adjacent venous tissue from Rhode Island Red roosters was characterized by measuring the isometric force developed following transmural nerve stimulation (TNS). During TNS, the valve relaxed while the iliac vein contracted. In the valve, a poststimulus contraction followed the relaxation. Propranolol and guanethidine abolished the TNS-induced relaxation of the valve, leaving a contraction that was increased by physostigmine and partially blocked by atropine or prazosin. In contrast, the TNS-induced contraction of the vein was blocked by guanethidine or prazosin. Measurement of choline acetyltransferase activity and norepinephrine content confirms that the valve is densely innervated with both cholinergic and adrenergic nerves. Thus the vein shows a predominantly adrenergic contractile response typical of most vascular smooth muscle, but the valve demonstrates a dual control, i.e., adrenergic nerves producing relaxation and cholinergic nerves causing contraction. Knowledge of the nature of neuronal control of the valve should aid in the design of experiments to determine its functional role.

The effects of gentamicin on tension responses to norepinephrine and KCl and Ca++ binding and fluxes in canine renal vein

The relaxant and inhibitory actions of gentamicin (Gent) on norepinephrine (NE)- and KCl-induced maximal contractions were delineated in canine renal vein, and subsequently correlated with Gent-induced effects on 45Ca uptake and efflux. Gent is a more potent inhibitor than a relaxant of KCl-induced contractions, whereas the opposite relationship exists for NE-induced contractions. Gent extensively inhibits (100%) or relaxes (82%) KCl-induced contractions. Prior exposure to Gent depresses NE-induced contractions by 68% and changes the response from a maintained to a phasic one. The initial, rapid upstroke is decreased in rat and magnitude. Maximum NE-induced contractions are rapidly relaxed (78%) by Gent. Gent is rinsed out more rapidly than NE, resulting in a secondary, transient contraction, which is concentration-dependent and only partially inhibited by D 600. Gent increases efflux into a 0 Ca++ solution in a maintained manner. Ca++ binding at La+++-sensitive and La+++-insensitive sites exhibiting high or low affinity characteristics are decreased appreciably (30-49%) by Gent. The high degree of sensitivity of canine renal vein to Gent results from Gent-induced effects on superficial membrane Ca++ binding sites, which are of significant importance in excitation/contraction (relaxation) coupling in venous smooth muscle.

Comparison of degree of dependence of canine renal arteries and veins on high and low affinity calcium for responses to norepinephrine and potassium

The relationships between tension responses to norepinephrine (NE) and high potassium (KCl) and high affinity 45Ca binding and mobilization were compared in canine renal arteries and veins. Contractile responses to 80 mM KCl were inhibited 83 (veins) and 88% (arteries) after respective 5-min and 60-min incubation periods in solutions with no added Ca++; responses to 10(-4) M NE were inhibited 87% (veins) and only 44% (arteries) after 60 min in the same solution. In solutions favoring low affinity binding of Ca++ (5.0 mM), uptake of 45Ca was similar in canine renal arteries and veins. However, in solutions favoring high affinity Ca++ binding (0.03 mM Ca++), 45Ca uptake was greater in arteries than in veins. Comparison of 45Ca efflux rates indicates a more rapid efflux and a greater Ca++-45Ca exchangeability in veins. After incubation with 45Ca and subsequent washout in an isosmotic (80.8 mM) La+++-substituted solution at 0.5 degrees C, 45Ca retention (residual Ca++ uptake) was proportionately greater in arteries than in veins at both high and low affinity sites. NE (10(-6) M) significantly increased La+++-resistant 45Ca uptake at both high and low affinity sites in veins but not in arteries. Thus, the NE-induced responses in veins depend upon extracellular Ca++ to a greater degree than in arteries. Even though veins have a lower number of high affinity Ca++ binding sites and this decreases the ability of the veins to retain sufficient Ca++ at these sites to maintain the response to NE, the responsiveness to NE appears to be maintained by an alternate mechanism, uptake of Ca++ at lower NE concentrations.

Renin-angiotensin-aldosterone system

There is increased activity of the renin, angiotensin, aldosterone (RAA) system in infancy and childhood. An inverse relationship between plasma renin, aldosterone and age has been demonstrated. In childhood hypertension due to renovascular disease or pyelonephritic scarring peripheral plasma renin is increased. Renal vein renin measurements in children with renal hypertension have proved valuable in predicting surgical curability of the underlying lesion. The upper limit of normal for the renal venous renin ratio in normotensive children without renal disease is 1.5. Pharmacological blockade of the RAA system has a place in diagnosis and treatment of hypertensive children. The plasma renin aldosterone profile is diagnostically useful in the investigation of salt-wasting disease and can easily distinguish between aldosterone biosynthetic defects and pseudohypoaldosteronism.

[Studies on the differential determination of renin activity in renal venous blood in renal artery stenosis]

Plasma renin activity (PRA) was determined in both renal veins of 37 patients with angiographically proven renal artery stenosis. Renal venous PRA was determined in 17 patients without furosemide stimulation and in 20 patients before and 15 and 30 min after intravenous injection of 40 mg furosemide. 21 of 37 patients showed abnormally high peripheral PRA. In the 17 patients in whom renal venous PRA was measured without stimulation, 11 showed a PRA ratio (PRA stenotic side/PRA unaffected side) greater than or equal to 1.5. The 20 patients in whom stimulation with furosemide was performed were divided into 2 groups each containing 10 patients: The first group was characterized by an increase in PRA ratio after furosemide stimulation, while in the second group this PRA ratio decreased. In the first group mean duration of hypertension was 4.5 years compared to 7.5 years in the second group. In 17 of 37 patients renal artery stenosis was corrected by surgery. After operation 12 patients became normotensive and in 2 patients hypertension improved. There was no effect of renovascular surgery on blood pressure in only 3 patients. None of these patients showed an increasing ratio in response to furosemide. Our results suggest that the validity of renal venous PRA measurements is enhanced when the procedure is performed before and after administration of furosemide.

[Lipids in the renal veins and disseminated intravascular coagulation]

Marked steatosis of glomeruli and of cortical arterioles is a peculiar and hitherto neglected change occuring in generalized Shwartzman's reaction as well as in the haemolytic-uremic syndrome. The fatty deposits originate during the transient hyperlipemia occurring in both the above entities. No comparable steatosis takes place in disseminated intravascular coagulation. In disseminated intravascular coagulation occurring in hyperlipemic rats, however, steatosis of glomeruli as well as of cortical arterioles is present so that the picture resembles generalized Shwartzman's reaction. Such a comparison poses a lot of further pathogenetic problems.

[Diagnostic and prognostic value of the separated renin in hypertension due to monolateral nephropathy]

Renin activity in renal vein plasma and in peripheral plasma was measured in twentytwo hypertensive patients presenting unilateral renal artery stenosis or other unilateral renal abnormalities. A discrepancy between peripheral and renal vein renin levels was noted only in one case. In seven patients the difference between the renal vein renin of the diseased kidney and that of its contralateral mate was very significant. They responded successfully to surgery for hypertension, confirming the predictive value of a renal vein renin ratio greater than 1.5. In all the other patients with less significant differences between the renin levels of the two kidneys surgery was not performed because they benefited from the hypotensive therapy.

Evidence for non-mast cell histamine in the vascular wall

Histamine has been found biochemically in the mammalian vascular wall. This study was undertaken in an effort to identify the presence of specific histamine-containing cells inwalls of large blood vessels such as femoral artery and vein, brachial artery and vein, mesenteric artery and vein, renal artery and vein, and aorta. Segments of vessels from rats, cats, dogs, sheep, cows, humans and chickens were examined. Sections were prepared from fresh tissue by vibratome, from frozen tissue by cryostat and from freeze-dried and fixed tissues. Mast cells were visualized by staining with acidic toluidine blue and by reaction with orthophthaladehyde to develop histamine fluorescence. Although mast cells were easily identified in preparations such as canine liver, ear and scrotal skin and rat tongue, no such cells were found in any species (except the cow) in any part of the vascular wall. The results indicate that in most species histamine is stored in the vascular wall in a non-mast cell pool which may well be in the smooth muscle cells themselves.

Renal vein renin studies in a patient with renal hilar pheochromocytoma and renal artery stenosis

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