Unilateral renal ischaemia in rats induces a rapid secretion of inflammatory markers to renal lymph and increased capillary permeability

A better understanding of the inflammatory process associated with renal ischaemia-reperfusion (IR) injury may be clinically important. In this study we examined the role of the kidney in production of inflammatory mediators by analysing renal lymph after 30 min unilateral occlusion of renal artery followed by 120 min reperfusion, as well as the effect of IR on size selectivity for proteins in both glomerular and peritubular capillaries. All measured mediators increased dramatically in renal hilar lymph, plasma and renal cortical tissue samples and returned to control levels after 120 min reperfusion. The responses were differentiated; interleukin-1β, monocyte chemoattractant protein-1 and leptin were markedly increased in plasma before reperfusion, reflecting an extrarenal response possibly induced by afferent renal nerve activity from the ischaemic kidney. Tumour necrosis factor-α was the only mediator showing elevated lymph-to-plasma ratio following 30 min reperfusion, indicating that most cytokines were released directly into the bloodstream. The IR-induced rise in cytokine levels was paralleled by a significant increase in high molecular weight plasma proteins in both lymph and urine. The latter was shown as a 14- to 166-fold increase in glomerular sieving coefficient of plasma proteins assessed by a novel proteomic approach, and indicated a temporarily reduced size selectivity of both glomerular and peritubular capillaries. Collectively, our data suggest that cytokines from the ischaemic kidney explain most of the rise in plasma concentration, and that the locally produced substances enter the systemic circulation through transport directly to plasma and not via the interstitium to lymph.

Adenosine sensitization after angiotensin II stimulation in afferent arterioles from normal rats does not occur during two-kidney, one-clip hypertension

AIMS

G protein-coupled receptors such as the AT(1a) R are frequently subject to desensitization, extensively studied in cell culture but to small extent in hypertensive models. Recently, angiotensin II (ANG II)-induced desensitization was shown to last 10 min in isolated afferent arterioles (AAs), suggesting impact on ANG II vasoactivity. In the present study, we explored ANG II desensitization and effects of adenosine (Ado) in AAs from two-kidney, one-clip (2K1C) hypertensive rats. Our main hypothesis was that Ado affects ANG II contractility differently in 2K1C, because of persistently elevated levels of ANG II.

METHODS

Afferent arterioles were isolated with the agarose-infusion/enzyme-treatment technique from normotensive and 2K1C hypertensive rats, and stimulated with ANG II (10(-7) M) at baseline and re-stimulated after 20 or 40 min, with or without Ado (2.5 × 10(-5) M) in the vessel bath.

RESULTS

Afferent arterioles from normotensive rats re-stimulated with ANG II after 20 min displayed a blunted contraction (Δ12.8 ± 4.3%, P < 0.05), which disappeared when AAs were stimulated after 40 min (Δ2.7 ± 2.3%, NS), indicating that desensitization lasted for 30 ± 10 min. Ado augmented ANG II contractions after 20 min, but not after 40 min, suggesting that only de-sensitized vessels were affected. Similar experiments in AAs from the clipped and non-clipped kidneys revealed no desensitization when re-stimulated with ANG II after 20 and 40 min, and contractions were unaffected by Ado.

CONCLUSIONS

Reduced duration of desensitization in AAs from 2K1C may cause vessels to be sensitized longer and increase vasoconstriction. The present study demonstrates that Ado does not augment ANG II-induced contractions in AAs from 2K1C as in normotensive rats, possibly because of a reduced period of desensitization.

Distribution and determinants of serum creatinine in the general population: the Hordaland Health Study

BACKGROUND

Serum creatinine is a well-recognized risk factor for cardiovascular disease (CVD) and is also a rough measure of glomerular filtration rate. The purpose of the present study was to investigate determinants of serum creatinine in the general population.

METHODS

The participants were recruited as a part of the Hordaland Health Study, and included 6952 men aged 41-49 years, 8218 women aged 41-49 years, 1470 men aged 71-74 years and 1865 women aged 71-74 years. Data on lifestyle factors, medical history and medication were obtained through questionnaires. Body size and blood pressure measurements as well as non-fasting blood samples were obtained during a health examination. Determinants of serum creatinine were identified using multiple linear and logistic regression analyses.

RESULTS

Male and older participants had higher levels of serum creatinine than female and middle-aged participants. For older participants, creatinine was associated with serum triglycerides, CVD, upper-arm circumference and use of antihypertensive drugs as well as inversely associated with cigarette smoking. For middle-aged participants, creatinine was associated with upper-arm circumference, serum lipids and physical exercise, as well as inversely associated with smoking and alcohol intake. The associations with CVD risk factors were much stronger for older participants than for middle-aged participants and most associations were significant after adjustments as well as present within the reference range of serum creatinine.

CONCLUSIONS

In this general population sample, high serum creatinine levels were associated with risk factors for CVD. These associations were stronger in older subjects, whereas in middle-aged subjects lifestyle variables were relatively more important.

Membrane filtration in microscopical examination of urinary sediment

Microscopical examination of the urinary sediment has been performed after membrane filtration and after routine centrifugation, and the results were compared. Various quantities of urine were filtered through a membrane with pore size of 3 micrometer, stained with Shorr stain and made translucent with xylol. All granular and cellular casts were counted on a trimmed membrane, 15 X 20 mm. The routine centrifugation was carried out on 10 ml urine at 1500 rpm for 3 min. Among 11 patients with glomerulonephrits and recurrent hematuria, casts were found in 9 after filtration but in only 2 after routine centrifugation. Casts were detected by the filter method in the urine after angiography of the kidneys in 8 of 12 patients, after centrifugation in only one of them. No casts were found in 6 patients with hematuria due to urological disorders and in 21 healthy persons. The diagnostic sensitivity of microscopical examination of urine was greatly increased by the filter method. This may be due to larger amount of urine examined by the filter method, but an additional cause may be that routine centrifugation destroys red cell casts.

Three-dimensional ultrasonography can detect the modulation of kidney volume in two-kidney, one-clip hypertensive rats

As volume changes are a typical finding in the two-kidney, one-clip hypertensive rat model (2K1C), it is of interest to investigate within what time frame these volume changes occur and their relation to hypertension. Kidney volume changes in Wistar rats were measured by three-dimensional (3D) ultrasonography (USG). Clipped induced stenosis was applied to the left renal artery in 11-wk-old animals (n = 8), using age-matched nonclipped rats as controls (n = 7). Ultrasonographic recordings were made before clipping and, thereafter, weekly with corresponding systolic blood pressure and body weight measurements. The nonclipped kidney showed increased volume at week 2, 5 and 7. Three wk after clipping, clipped kidneys were smaller than the nonclipped kidneys (0.47 +/- 0.11 mL versus 1.28 +/- 0.07 mL). No difference was found between the left and right kidney in the control group at any week. Blood pressure was significantly higher in the 2K1C hypertensive group 4 weeks after clipping (201 +/- 16 versus 139 +/- 4 mm Hg) with stable blood pressure thereafter. Three-dimensional USG showed that clipping caused a decrease in kidney volume from week 3 in the clipped kidney and a volume increase in the nonclipped kidney at week 2. A significant increase in blood pressure appeared after week 4.

Differential effect of tetradecythioacetic acid on the renin-angiotensin system and blood pressure in SHR and 2-kidney, 1-clip hypertension

The tetradecythioacetic acid (TTA) is a modified fatty acid known to exhibit pleiotropic effects. First, we compared the effect of TTA on the blood pressure in spontaneously hypertensive rats (SHR) with two-kidney, one-clip (2K1C)-hypertensive rats. Second, we examined mechanisms involved in the blood pressure reduction. TTA had minor effect on systolic blood pressure (SBP) in young SHR up to 8 wk of age. In 2K1C we confirmed the blood pressure-lowering effect of TTA (SBP: 173 ± 4 before vs. 138 ± 3 mmHg after TTA, P < 0.001). No effect on SBP was seen in Wistar-Kyoto rat (WKY) controls. Plasma renin activity (PRA) was low in SHR and WKY controls and TTA did not change it. PRA decreased from 22.9 ± 1.3 to 16.2 ± 2.2 ng·ml−1·h−1 ( P = 0.02) in 2K1C. Plasma ANG II concentration declined from 101 ± 3 to 81 ± 5 fmol/l after TTA treatment ( P = 0.005). In the clipped kidney, tissue ANG I concentration decreased from 933 ± 68 to 518 ± 60 fmol/g tissue ( P = 0.001), and ANG II decreased from 527 ± 38 to 149 ± 21 fmol/g tissue ( P < 0.001) after TTA treatment. In the nonclipped kidney, TTA did not change ANG I and moderately reduced ANG II levels. The renal blood flow response to injection of ANG II into the nonclipped kidney was blunted compared with controls and normalized with TTA treatment (10 ± 2 before vs. 20 ± 2%, P < 0.001). The results indicate that TTA downregulates the renin-angiotensin system in high renin animals but has no effect in low renin models.

Focal and segmental glomerular sclerosis (FSGS) in a man and a woman with Fabry's disease

We describe a man and a woman with Fabry's disease. Renal biopsies showed late and early stages respectively of focal and segmental glomerulosclerosis (FSGS) and vascular changes. Clinically the hemizygous patient had advanced renal disease with nephrotic range proteinuria and serum creatinine 122 micromol/l. The female carrier had minimal albuminuria, borderline GFR with a normal serum creatinine, acroparesthesias, moderate fatigue, tinnitus and headache accompanied by ischemic cerebral lesions. Enzyme replacement therapy (ERT) was initiated according to our Fabry protocol, partly due to the renal morphologic findings. We conclude that FSGS and vascular changes may be an early morphologic finding in Fabry's disease, even in patients with subtle albuminuria. The potential role of FSGS as a marker of progressive renal disease in some Fabry patients is discussed. As FSGS and vascular changes obviously may exist across a wide range of clinical presentations and have potential prognostic implications, we suggest that a renal biopsy should be performed prior to enzyme replacement therapy in all adult Fabry patients with proteinuria of various levels. Efforts should be made to develop a scoring system to evaluate potential histologic markers. Protocol biopsies may have therapeutic implications and may provide valuable information in the evaluation of start and dosing of ERT.

Critical renal artery stenoses may cause a spectrum of cardiorenal failure and associated thromboembolic events

A wide spectrum of acute or chronic heart failure and thromboembolic events may be causally related to high-grade uni- or bilateral renovascular hypertensive disease, and the variety of these potential interactions may be unrecognized in clinical practice. We present three cases that illustrate the clinical variability of cardiorenal failure and thromboembolic events seen in patients with significant renal artery stenoses. These are high-risk patients where severe morbidity and mortality are threatening. Our patients also demonstrate that the diagnosis often is delayed, and that recanalizing of occluded renal arteries may be highly cost-effective and life-saving in such patients.

The renal vascular response to ANG II injection is reduced in the nonclipped kidney of two-kidney, one-clip hypertension

The ANG II receptor 1 (AT(1)R) level in the nonclipped kidney of two-kidney, one-clip hypertension (2K1C) has shown to be unchanged despite a high circulating angiotensin (ANG) II level. To examine the vasoreactive response to ANG II in this kidney, injections of ANG II into renal artery were performed 6 wk after clipping of the kidney and compared with normotensive controls. The renal blood flow (RBF) response to 2.5 ng ANG II was measured by a Transonic transit-time flowmeter, before and after indomethacin and candesartan treatment, and analyzed by a computer program. The RBF response to 5 ng arginine-vasopressin (AVP) was examined for comparison with ANG II. The mRNA for AT(1A) and AT(1B) as well as Western blotting for AT(1)R in renal resistance vessels were determined, and plasma renin activity (PRA) was measured. Systolic blood pressure was 183 +/- 4 mmHg in 2K1C rats compared with 113 +/- 1 mmHg in controls (P < 0.001). PRA was significantly increased in 2K1C animals (P < 0.05). Injection of ANG II reduced RBF with 10 +/- 2% in the nonclipped kidney and 24 +/- 3% in controls (P < 0.001). After indomethacin, the RBF response increased from 10 +/- 2 to 20 +/- 3% (P < 0.02) in 2K1C rats and from 24 +/- 3 to 34 +/- 6% in controls (P < 0.01). The doses of candesartan needed to completely inhibit RBF response to ANG II were 30 microg/kg in the nonclipped kidney and 100 microg/kg in controls (P < 0.001). Western blotting and mRNA for AT(1A) and AT(1B) in the nonclipped kidney were similar to the controls. The results indicate that despite no difference in total AT(1)R levels, functional AT(1)R is downregulated in the nonclipped kidney of 2K1C rats.

Characterization of Ribosomal P Autoantibodies in Relation to Cell Destruction and Autoimmune Disease

Autoantibodies against the ribosomal P proteins are related to cell death and tissue destruction and are frequently exhibited in patients with systemic lupus erythematosus (SLE). In an attempt to explore the effect of tissue destruction on the induction of anti-P autoantibodies, we searched for anti-P autoantibodies by enzyme-linked immunosorbent assay in 201 antinuclear antibody (ANA)-positive individuals, in 10 patients with treated kidney SLE and in 45 acute leukaemia patients undergoing intensive chemotherapy. The autoantibody reactivity was further characterized using one- and two-dimensional immunoblot analysis and immunofluorescence. Anti-P were detected in 5.5% (11/201) of ANA-positive individuals, but not in kidney-affected SLE patients or in patients with leukaemia. Seven of 11 anti-P-positive patients had SLE (3/11), primary Sjögrens's syndrome (1/11) and other autoimmune diseases (3/11). A relation between disease activity and anti-P was suggested by follow-up examinations in one SLE patient, supported by the absence of anti-P autoantibodies in the 10 treated kidney SLE patients. Anti-P autoantibodies were detected by immunoblot in one patient with SLE indicating anti-P2 predominance and in the patient with Sjögrens's syndrome indicating anti-P1 predominance. Diverging humoral responses in these ANA- and anti-P-positive patients were further illustrated by immunofluorescence, elucidating varying nuclear reactivity and anti-P pattern. The observation of anti-P in individuals with active autoimmune disease, but not in patients with chemotherapy-induced cell damage, suggests that anti-P antibodies are part of a specific disease process, and not elicited as a response to cell destruction per se.

Effect of light exercise on renal hemodynamics in patients with hypertension and chronic renal disease

OBJECTIVE

Increased physical activity is followed by a stimulation of the sympathetic nervous system and this effect is probably more pronounced in patients with chronic renal failure and hypertension than in healthy controls. The role of sustained exercise in hypertensive patients with chronic renal failure, with and without antihypertensive therapy, is unclear, as is hormonal regulation of the renal hemodynamics. We hypothesized that prolonged low-intensity bicycle exercise would have a greater effect in patients with chronic renal failure than in controls, and that antihypertensive treatment would ameliorate these effects.

MATERIAL AND METHODS

Glomerular filtration rate (GFR), effective renal plasma flow (ERPF), mean arterial blood pressure (MAP), norepinephrine (NE) and atrial natriuretic peptide (ANP) were measured in the upright position before and during low-intensity exercise for 2 h in healthy controls (n = 8) and in hypertensive patients with moderately reduced renal function who were not taking antihypertensives (n = 7) or who were receiving treatment with captopril (n = 10), enalapril (n = 6) or verapamil (n = 9).

RESULTS

GFR tended to decrease and ERPF decreased significantly in healthy individuals when exercise duration was prolonged from 1 to 2 h. An earlier decline in GFR and ERPF was seen in the renal failure patients compared with the controls. Filtration fraction (FF) increased during exercise in all groups except the group taking enalapril. MAP increased in the captopril group during exercise but was unchanged in the other groups. Treatment with captopril produced a more pronounced and earlier fall in exercise-induced GFR than in untreated controls, while verapamil treatment completely blunted the decline in GFR, with a concomitant increase in plasma ANP. No significant changes were seen in plasma NE levels, but urinary NE excretion increased in controls and captopril-treated patients during exercise.

CONCLUSIONS

The results suggest that prolonged low-intensity exercise has a substantially greater effect on renal hemodynamics in hypertensive renal failure patients than in healthy controls, with negligible changes in plasma NE levels. Verapamil treatment seems to ameliorate the renal effects of exercise on GFR in these patients, and this may in part be mediated via a stimulatory effect on ANP.

Ambulatory blood pressure in patients with mesangial proliferative glomerulonephritis

Twenty-four-hour ambulatory blood pressure was measured in seven normotensive and 10 hypertensive patients with biopsy proven mesangial proliferative glomerulonephritis (MPG). In normotensive patients, the nocturnal blood pressure variation was seen with a nightly drop in blood pressure while in hypertensive patients with MPG, 24-h blood pressure level was increased both at day- and night-time, but a nocturnal change in blood pressure was also observed in these patients. The pattern of blood pressure variation was not, however, different from the normotensive patients. None of the hypertensive patients with MPG was a so-called non-dipper, showing the same level of blood pressure both at day- and night-time. The hypertensive patients had a rapid increase in blood pressure in the early morning hours from 06.00 to 09.00 h, followed by a relatively abrupt decrease in blood pressure in the evening hours. The patients with high blood pressure were treated with antihypertensive drugs; all patients started with captopril 25 mg once a day, later increasing to twice daily. If the correction of the high blood pressure was not achieved with this drug, amlodipine 5 or 10 mg was added with or without furosemide. Most of the patients needed more than one drug. In all patients, a normal 24-h ambulatory blood pressure could be obtained. The lack of nightly non-dippers in the present hypertensive patients may be explained by a relatively short history of renal disease and the presence of normal or moderately reduced glomerular filtration rate. The abrupt rise in blood pressure during the early morning hours may be due to activation of the renin-angiotensin or sympathetic nervous system in the hypertensive patients with MPG.

Renal hemodynamics in young and old spontaneously hypertensive rats during intrarenal infusion of arginine vasopressin

BACKGROUND/AIMS

To gain insight into the effect of arginine vasopressin (AVP) on renal hemodynamics in hypertensive rats, we investigated the vasoconstrictive response to AVP on total renal blood flow (RBF) and total and zonal glomerular filtration rate (GFR) in young and old spontaneously hypertensive rats (SHR). A hypothesis of increased AVP sensitivity in the juxtamedullary cortex of SHR was tested.

METHODS

Total RBF and total and zonal GFR were studied in 10- and 40-week-old SHR and normotensive Wistar-Kyoto rats (WKY). RBF was recorded by a flowmeter before infusion of AVP and immediately after injection of a bolus dose of 10 ng AVP. Whole kidney GFR and its intracortical distribution was measured by the tubular uptake of 125I- and 131I-labelled aprotinin before and during a continuous infusion of AVP 5 ng/min. Ligand binding measurements of preglomerular V1a receptors were performed in young and old rats.

RESULTS

RBF decreased by 43 +/- 3% in 10-week SHR (9.2 +/- 0.5 vs. 5.2 +/- 0.3 ml x min(-1) x g(-1)), significantly more than 10-week WKY where RBF decreased by 35 +/- 3% (9.6 +/- 0.7 vs. 6.5 +/- 0.5 ml x min(-1) x g(-1)) (p < 0.05). The effect of AVP on RBF was attenuated in 40-week-old rats where the decline in RBF was 29 +/- 5% in SHR and 23 +/- 4% in WKY (p > 0.05). GFR decreased by 6 +/- 3% (1.03 +/- 0.04 vs. 0.96 +/- 0.04 ml x min(-1) x g(-1), p < 0.05) in 10-week SHR and was unchanged in 10-week WKY (1.10 +/- 0.07 vs. 1.08 +/- 0.04 ml x min(-1) x g(-1), p > 0.10). GFR decreased by 11 +/- 10% in 40-week SHR and by 4 +/- 4% in 40-week WKY (p > 0.05). AVP infusion significantly increased filtration fraction in all groups except 40-week SHR, indicating that AVP has the strongest vasoconstrictive effect on postglomerular vessels. The intrarenal distribution of GFR was unchanged in the normotensive and hypertensive groups. V1a receptor density was upregulated in young SHR compared to young WKY (p < 0.05), but downregulated in old compared to young SHR (p = 0.05).

CONCLUSION

The results indicate that AVP sensitivity is not increased in the juxtamedullary cortex in SHR and the reduced vasoconstrictive effect in old SHR is due to a reduced density of V1a receptors.

Plasmapheresis in the treatment of steroid-dependent bronchial asthma

BACKGROUND

Can plasmapheresis improve disease severity and lung function and reduce steroid doses in severe asthma patients dependent on oral corticosteroids?

METHODS

A pilot study with four asthma patients was undertaken using PEF (peak expiratory flow) symptom score, number of puffs of beta2-agonist, and dose of systemic steroids as disease variables. After at least an 8-week run-in, the patients were randomized to a crossover treatment regimen consisting of either 10 days of plasmapheresis or placebo treatment. Each treatment was succeeded by an 8-26-week follow-up period.

RESULTS

No patients achieved a significant effect of plasmapheresis treatment according to the established criteria, nor did anyone experience deterioration.

CONCLUSIONS

Removing humoral factors extensively over a 10-day period did not significantly influence the clinical condition of the four steroid-dependent asthma patients studied. Circulating humoral factors seem to be of little importance for the maintenance of the established chronic allergic inflammation in these patients. Plasmapheresis does not seem to be a treatment option for this patient category.

Sympathetic nervous system overactivity in hypertensive patients with chronic renal failure--role of upright body position

OBJECTIVE

The renal functional consequences of an activated sympathetic nervous system and plasma atrial natriuretic hormone (ANP) in various renal diseases are not well described. We hypothesize that norepinephrine (NE) and ANP have antagonizing effects on renal hemodynamics in diseased kidneys.

MATERIAL AND METHODS

Plasma NE, ANP. glomerular filtration rate (GFR), effective renal plasma flow (ERPF) and mean arterial pressure (MAP) were measured in the upright position in healthy controls (n = 9) and hypertensive patients with reduced GFR (n =11). The same parameters were compared between healthy controls (n = 6) and hypertensive patients with reduced GFR (n = 6) in upright and supine positions.

RESULTS

Upright plasma NE and ANP were significantly elevated in the patients compared with the controls (4.4 +/- 0.4 vs 2.1 +/- 0.2 nmol/l (p < 0.001) and 1.3.5 +/- 2.1 vs 6.9 +/- 1.0 nmol/l (p < 0.01) respectively). With change from upright to supine position plasma NE decreased in the controls (2.2 +/- 0.3 vs 1.7 +/- 0.3 nmol/l) (p < 0.01) and patients (3.8 +/- 0.4 vs 2.6 +/- 0.4) (p < 0.01). Supine ANP increased in controls (5.5 +/- 1.0 vs 8.3 +/- 1.1) (p < 0.01) but not in patients (14.3 +/- 3.8 vs 16.1 +/- 3.8 nmol/l) (p > 0.10). Plasma NE correlated positively with MAP (p < 0.001) and negatively with GFR (p < 0.01) in the upright but not supine position. A positive correlation between NE and ANP was observed in upright (p < 0.001) but not in supine position. ANP correlated negatively with GFR in the upright (p < 0.01) but not supine position. No position dependent changes were seen in GFR and ERPF, but supine filtration fraction (FF) increased insignificantly in the patient group (0.23 +/- 0.02 vs 0.24 +/- 0.02) (p < 0.05).

CONCLUSION

Hypertensive patients with reduced GFR have elevated levels of plasma NE and ANP in the upright body position. When the upright and supine positions are compared, plasma NE declines in the supine position in controls and hypertensive renal failure patients. and plasma ANP levels are elevated only in the upright position in hypertensive renal failure patients where the sympathetic nervous system is activated. A significant positive relationship between plasma NE and ANP was observed only in the upright position. The upright body position seems superior to recumbency in the characterization of these hormonal changes in hypertensive chronic renal failure patients.

Wegener's granulomatosis: inflammatory cells and markers of repair and fibrosis in renal biopsies--a clinicopathological study

OBJECTIVE

This study aimed to quantitate inflammatory cells in renal biopsies from patients with Wegener's granulomatosis (WG) and to identify cells participating in early fibrogenesis. The goal was to determine whether these cells correlated with the severity of renal disease and whether their presence had a bearing on renal prognosis.

MATERIAL AND METHODS

Sixty-one patients with WG who had a renal biopsy taken at the time of diagnosis were included in the study. Immunostaining with monoclonal antibodies towards macrophages (CD68), T- and B-lymphocytes, alpha-smooth muscle actin (alpha-SMA) and vimentin was done.

RESULTS

The dominating intraglomerular leucocytes were macrophages (29.9 +/- 15 cells/glomerular cross-section) and to a lesser extent T-cells (2.57 +/- 1.8 cells/glomerular cross-section). No B-lymphocytes were detected in the glomeruli. More than two-thirds of the T-cells were CD8+ (cytotoxic) cells. Macrophages and T-lymphocytes were distributed equally in the renal interstitium and were numerous around crescentic glomeruli. Glomerular and interstitial macrophages and interstitial T-cells correlated significantly with serum (S-) creatinine at the time of biopsy but not after 1 year. S-creatinine at the time of biopsy and after 1 year differed significantly among the three levels of interstitial alpha-SMA staining. S-creatinine at biopsy was highest when tubular vimentin staining was strongest, and tubular vimentin staining was strongest in patients with acute tubular damage.

CONCLUSIONS

Evidence was found for a cellular type IV immune response in WG, with CD8+ T-lymphocytes and macrophages dominating the cellular infiltrate. The detection of interstitial alpha-SMA, probably staining myofibroblasts implicated in renal fibrogenesis, indicated a low glomerular filtration rate 1 year after renal biopsy.

Renal hemodynamic effects of captopril and doxazosin during slight physical activity in hypertensive patients with type-1 diabetes mellitus

Angiotensin-converting enzyme inhibitors are renoprotective in diabetes mellitus through their intrarenal hemodynamic effects. Alpha-1 blockade has variable pre- and postglomerular vasodilatory effects dependent upon the stimulation of the sympathetic nervous system. We tested the hypothesis that the two different classes of drugs have similar renal hemodynamic effects when the patients are examined in an upright position where the sympathetic nervous system is activated. Mean blood pressure (MAP), glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were examined in 28 hypertensive type-1 diabetic patients with variable degree of nephropathy treated for a mean period of 7.6 +/- 0.4 months with captopril (n = 13) or doxazosin (n = 15). Average treatment doses were 112 +/- 7 mg/day in the captopril group and 8 +/- 1 mg/day in the doxazosin group. Sitting MAP decreased from 118 +/- 3 to 106 +/- 4 mm Hg after captopril (p < 0.05), and from 117 +/- 4 to 110 +/- 3 mm Hg after doxazosin (p = 0.07). GFR and ERPF were unchanged in both groups. The filtration fraction (FF) decreased from 0.27 +/- 0.02 to 0.25 +/- 0.02 after captopril (p < 0.05) and from 0.26 +/- 0.01 to 0.25 +/- 0.01 after doxazosin (p = 0.08). Calculation of 95% confidence intervals of the difference between the post-treatment values as well as the difference between pre- and post-treatment values of MAP, GFR, ERPF and FF of the two drugs indicates no difference in renal hemodynamic response between the drugs. In conclusion, captopril and doxazosin have similar renal hemodynamic responses when the patients are examined in a situation where the sympathetic nervous system is stimulated, and this suggests that doxazosin has a renoprotective effect beyond the blood pressure-lowering effect.

[Emergency dialysis at Haukeland hospital in 1999]

BACKGROUND

The incidence of acute renal failure requiring dialysis is not known in our country. The criteria for acute dialysis are not uniformly accepted, neither is there consensus on dialysis strategy in critically ill patients. We describe the acute dialysis activity in our hospital in 1999.

MATERIAL AND METHODS

We have retrospectively recorded the indications for dialysis and the course and hospital mortality in all patients treated with acute dialysis in 1999.

RESULTS

108 patients were treated with 670 dialysis procedures; the incidence was 20.5 per 100,000 inhabitants. Continuous veno-venous haemodiafiltration accounted for 37% of all treatments. In 50% of the patients acute renal failure occurred after surgery or serious infections with a mortality of 57% and 62% respectively. Total dialysis mortality was 45%. The mortality in patients with malignancy and peripheral vascular disease was 90% and 75% respectively. 10% of the patients needed chronic dialysis.

INTERPRETATION

The incidence of acute dialysis was higher than previously reported from European countries and may be related to the general increase in active treatment of patients with complicated diseases. The mortality rates are persistently high. Close cooperation between nephrologists and intensivists in the treatment of these patients is essential.

[Acute renal failure, renal artery stenosis and angiotensin-converting enzyme (ACE) inhibitor]

BACKGROUND

Acute renal failure is a well-known complication in patients with renal artery stenosis during treatment with ACE inhibitor. Renal artery thrombosis after withdrawal of ACE inhibitor has not been reported previously.

MATERIAL AND METHODS

We describe a patient with acute renal failure with an unexpected course.

RESULTS

A 67-year-old man was admitted with acute anuric renal failure during treatment with hydrochlorothiazide and enalapril. His blood pressure was 165/60 mm Hg. Renal ultrasound was normal. After initial rehydration and dialysis, diuresis resumed until a sudden unexpected anuric renal failure recurred on day 12. Angiography disclosed bilateral renal artery occlusion. The right renal artery was successfully opened and a stenosis was blocked and stented, and brisk diuresis ensued. Two days later hypertension accelerated, and a new invasive procedure on day 24 succeeded in opening, blocking and stenting a proximal stenosis in the left artery; a mobile thrombus was located behind the stenosis and successfully treated with intraarterial thrombolysis. Blood pressure rapidly normalized, and serum creatinine was normal on visits 1.5 and 4 months later.

INTERPRETATION

General aspects and prevention of acute renal failure during ACE inhibitor therapy are discussed. Acute renal thrombosis after withdrawal of ACE inhibitor in patients with stimulated renin angiotensin system and significant renal artery stenosis may be causally related to the antifibrinolytic effects of angiotensin II and aldosterone. Endovascular reconstruction of renal artery occlusion may completely restore the kidney function.

Renal histopathology and clinical course in 94 patients with Wegener's granulomatosis

BACKGROUND

The main purpose of this study was to examine histopathological changes seen in renal biopsies from patients with Wegener's granulomatosis (WG) with varying degrees of renal involvement and to study possible correlations between the morphological variables and the severity of the disease.

METHODS

Ninety-four patients with WG and active renal disease were included in this retrospective study. All patients had a percutaneous renal biopsy taken on their first admission to the hospital and 14 patients had a second biopsy. The patients were followed for a median of 42.5 months (range 0.5-184).

RESULTS

Segmental necrotizing glomerulonephritis and extracapillary proliferation were present in 85.1 and 91.5% respectively. Of seven patients (7.4%) with normal serum creatinine and urinary protein excretion <0.5 g/day, all had crescents and six had segmental glomerular necrosis. Serum creatinine at biopsy correlated significantly with the percentage of glomeruli with crescents (rho=0.52, P=0.0004), with necrosis (rho=0.36, P=0.002) and with the percentage of normal glomeruli (rho=-0.55, P=0.0003). On a multivariate analysis, only the percentage of normal glomeruli was significantly associated with renal function and development of end-stage renal disease. In 14 second biopsies after a mean of 41.2 (+/-26) months, chronicity scores had increased significantly in 13 biopsies in spite of full immunosuppressive treatment.

CONCLUSION

Although renal biopsy is of value in defining renal involvement in WG, it is of limited help in the early stage of the disease in predicting renal outcome for the individual patient. A follow-up biopsy can be useful in revealing the degree of activity and chronicity and hence be of importance for the choice of further therapy.

Role of nitric oxide in the autoregulation of renal blood flow and glomerular filtration rate in aging spontaneously hypertensive rats

Autoregulation of renal blood flow (RBF) and glomerular filtration rate (GFR) is well maintained in the spontaneously hypertensive rat (SHR). In old SHR, the RBF autoregulation is dependent upon prostaglandins as well as the sympathetic nervous system. The purpose of this study was to examine the role of nitric oxide (NO) in the autoregulation of RBF and GFR in aging SHR (70 weeks) as compared with young SHR (10 weeks) and age-matched Wistar-Kyoto (WKY) rats using NO synthase (NOS) inhibition that has a minimal effect on the RBF. The autoregulation of RBF was examined using an adjustable aortic clamp above the renal arteries and an ultrasound Doppler flow probe on the left renal artery. The lower pressure limit of RBF autoregulation was examined before and after infusion of the NOS inhibitor N(G)-monometyl-L-arginine (L-NMMA; 500 microg. kg(-1).min(-1)). Separate groups were given a coinfusion of L-NMMA and L-arginine (5 mg.kg(-1).min(-1)) or Ringer solution. The autoregulation of the GFR was studied in continuously infused animals using the (125)I-iothalamate clearance. Measurements of the GFR were done at control blood pressure, at a renal arterial pressure 10 mmHg above the lower pressure limit of RBF autoregulation and at a renal arterial pressure of about 60-65 mmHg. In both SHR and WKY rats, infusion of L-NMMA increased the mean arterial blood pressure, and the RBF decreased in young SHR, while the RBF was unchanged in the WKY groups and aged SHR. The autoregulation of RBF was maintained in all animals. The GFR was unchanged in all groups after infusion of L-NMMA, and the autoregulation of GFR was well maintained in all groups except in the 70-week-old SHR. In these animals, the fractional compensation of GFR decreased from 0.95 to approximately 0 after infusion of L-NMMA, indicating that autoregulation of the GFR was lost during NOS inhibition. Coinfusion of L-NMMA and L-arginine normalized the GFR autoregulation in this group. The results indicate that in hypertensive rats with renal hypertensive damage, the GFR autoregulation is strongly NO dependent, as doses of L-NMMA that do not interfere with the RBF have an effect on the GFR autoregulation. As the GFR was unchanged during L-NMMA infusion, these observations suggest that postglomerular contraction during NOS inhibition may be involved in the regulation of GFR in 70-week-old SHR.

[Water channels of the cell--aquaporins]

BACKGROUND

Several mechanisms in the body regulate the water transport within the cells up and down during physiological and pathological conditions. The discovery of aquaporins, water channel proteins, has brought more insight into and understanding of how water crosses plasma membranes within cells in body tissue.

MATERIAL AND METHODS

The functions of aquaporins are not fully understood; this paper summarise current knowledge of various aquaporins.

RESULTS

Known aquaporins are discussed in relation to some physiological, pathological and clinical conditions.

INTERPRETATION

In the future, measurements of aquaporin concentrations in urine and possibly in other samples will give us a broader picture of water exchange and a better understanding of the mechanisms underlying water production in clinical states like renal and heart failure and liver insufficiency. Moreover, by manipulating water channel proteins by compounds developed for this purpose, one may have a tool for treating some clinical disorders in which water depletion or water overload is an important factor.

Upregulation of V(1) receptors in renal resistance vessels of rats developing genetic hypertension

Previous studies have demonstrated that arginine vasopressin (AVP) produces exaggerated renal vasoconstriction in young spontaneously hypertensive rats (SHR) relative to normotensive rats. The exaggerated renal vascular reactivity does not appear to be due to a primary defect in postreceptor calcium signal transduction. Although the magnitudes of vascular responses differ, the relative proportions of calcium entry and mobilization pathways evoked by AVP in renal resistance vessels are similar in these rat strains. The purpose of the present study was to evaluate possible differences in V(1) mRNA and receptor density and affinity in preglomerular resistance vessels (<50 microm) obtained from young Wistar-Kyoto (WKY) and SHR. Quantitative RT-PCR analysis revealed twofold greater expression of the V(1a) receptor gene in preglomerular arterioles of 7-wk-old SHR compared with WKY. In vitro radiolabeled ligand binding studies were performed under equilibrium conditions on preglomerular resistance arterioles freshly isolated from kidneys of 7-wk-old rats. The results indicate that AVP receptor density (B(max)) is two to three times greater in SHR than in WKY (248 +/- 24 vs. 91 +/- 11 fmol/mg protein, P < 0.001). The affinity does not differ between strains (K(d) = 0.5 nM). Displacement studies yielded similar results for SHR and WKY. Unlabeled AVP completely displaced [(3)H]AVP binding, with an IC(50) of 2.5 x 10(-10) M. Expression of AVP receptor types in afferent arterioles was evaluated using the V(1) receptor agonist, [Phe(2), Ile(3),Org(8)]vasopressin, the V(1) receptor antagonist, [d(CH(2))(5), Tyr(Me)(2), Tyr(NH(2))(9)]Arg(8)-vasopressin, and the V(2) receptor agonist, desamino-[D-Arg(8)]vasopressin. Both the V(1) agonist and antagonist displaced up to 90% of the AVP binding with IC(50) values of 4 x 10(-8) and 8 x 10(-7) M, respectively. The V(2) receptor agonist was a weak inhibitor, displacing less than 15% of AVP binding at a high concentration of 10(-4) M. These results demonstrate that virtually all AVP receptors in the preglomerular arterioles are of the V(1) type. Collectively, our results provide evidence that the enhanced renal reactivity to AVP is mediated by a higher density of V(1) receptors associated with increased gene expression in renal resistance vessels of SHR developing genetic hypertension.

Wegener's granulomatosis: clinical course in 108 patients with renal involvement

BACKGROUND

The aim of this study was to evaluate the clinical course of patients with Wegener's granulomatosis and renal involvement, with special reference to relapse rate, renal and patient survival and morbidity from serious infections.

METHODS

A retrospective analysis was carried out of 108 patients presenting with Wegener's granulomatosis and active renal disease in eight hospitals in Norway between 1988 and 1998. Multivariate analysis was used to investigate whether selected variables predicted relapse, renal and patient survival and serious infections.

RESULTS

Median follow-up was 41.5 months. Twenty-two patients (20.4%) were admitted with a need for dialysis. Complete remission was obtained in 81.5% after a median of 4 months, and 54.7% relapsed after a median of 22. 5 months. Two- and five-year renal survival was 86 and 75%, respectively, and 22.8% developed end-stage renal disease (ESRD). Two- and five-year patient survival was 88 and 74%, respectively, and the cumulative mortality was 3.8 times higher than expected. The relative risk of relapse increased with the use of intravenous pulse cyclophosphamide compared with daily oral cyclophosphamide. Initial renal function predicted renal survival, and low serum albumin and high age at treatment start increased the mortality risk. Thirty one per cent of the patients were hospitalized for serious infections during follow-up. Old age increased the risk of having an infection.

CONCLUSIONS

The current treatment of Wegener's granulomatosis does not prevent relapse, development of ESRD and serious treatment-induced infections in a considerable fraction of the patients. Alternative strategies for the management of this disease will be an important objective for further studies.

Exaggerated Ca2+ signaling in preglomerular arteriolar smooth muscle cells of genetically hypertensive rats

Experiments were conducted to gain insight into mechanisms responsible for exaggerated renal vascular reactivity to ANG II and vasopressin (AVP) in spontaneously hypertensive rats (SHR) during the development of hypertension. Cytosolic calcium concentration ([Ca2+]i) was measured by ratiometric fura 2 fluorescence and a microscope-based photometer. Vascular smooth muscle cells (SMC) from preglomerular arterioles were isolated and dispersed using an iron oxide-sieving method plus collagenase treatment. ANG II and AVP produced rapid and sustained increases in [Ca2+]i. ANG II elicited similar dose-dependent increases in [Ca2+]i in SMC from SHR and Wistar-Kyoto rats (WKY). In contrast, AVP caused almost twofold larger responses in afferent arteriolar SMC from SHR. ANG II effects were inhibited by the AT1 receptor antagonist losartan. AVP action was blocked by the V1 receptor antagonist [d(CH2)5,Tyr(NH2)9]AVP. In SMC pretreated with nifedipine, neither ANG II nor AVP elicited [Ca2+]i responses. Poststimulation nifedipine reversed elevated [Ca2+]i to basal levels. Short-term reductions in external [Ca2+]i (EGTA) mimicked the nifedipine effects. Our study shows that AT1 and V1 receptors stimulate [Ca2+]i by a common mechanism characterized by preferential action on voltage-gated L-type channels sensitive to dihydropyridines. Calcium signaling elicited by AT1 receptors does not differ between SHR and WKY; thus the in vivo exaggerated reactivity may be dependent on interactions with other cell types, e. g., endothelium. In contrast, AVP produced larger changes in [Ca2+]i in arteriolar SMC from SHR, and such direct effects can account for the exaggerated renal blood flow responses.

AT1 calcium signaling in renal vascular smooth muscle cells

Experiments were conducted to gain insight into calcium signaling mechanisms triggered by angiotensin II (AngII) stimulation in vascular smooth muscle cells (SMC) freshly isolated from preglomerular vessels of normotensive Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). Cytosolic calcium concentration ([Ca2+]i) was measured using ratiometric Fura-2 fluorescence and a microscope-based photometer. Vascular SMC from preglomerular vessels were isolated and dispersed using an iron oxide-sieving method combined with collagenase treatment. AngII produced rapid increases in [Ca2+]i that remained elevated for the duration of continued stimulation. The same pattern of time response was observed in WKY and in SHR. AngII elicited dose-dependent increases in [Ca2+]i in groups of individual preglomerular arteriolar SMC from both strains. AngII (10(-10) M) induced an increase from baseline levels in WKY and SHR (37+/-9 and 32+/-13 nM; P < 0.05). In response to 10(-6) M AngII, steady-state responses were 165+/-30 and 170+/-35 nM (P < 0.01). The responses did not differ between strains (P > 0.4). The effects of AngII were inhibited by 88% by the AT1 receptor blocker candesartan in renal SMC. In SMC pretreated with calcium-free medium, baseline [Ca2+]i fell by about 60 nM. Thereafter, AngII did not elicit any [Ca2+]i response either in WKY or in SHR when calcium entry was prevented. Also, after prestimulation by AngII, a calcium-free solution completely reversed the effects of AngII. This study shows that AngII acts through AT1 receptors to stimulate [Ca2+]i by a predominant action on calcium entry with no evidence for calcium mobilization. Other studies have demonstrated that calcium entry in these SMC is mediated by voltage-gated, L-type entry channels sensitive to dihydropyridine agents. No strain differences were noted between the actions of AngII on individual renal SMC from SHR and normotensive control animals.

Effects of antihypertensive drugs on autoregulation of RBF and glomerular capillary pressure in SHR

The relationship between systemic blood pressure and glomerular capillary pressure (Pgc) in spontaneously hypertensive rats (SHR) during treatment with antihypertensive drugs is still unclear. The effects of an angiotensin-converting enzyme inhibitor (enalapril), two calcium channel antagonists (nifedipine and verapamil), and an alpha1-receptor blocker (doxazosin) on renal blood flow (RBF) autoregulation, Pgc, and renal segmental resistances were therefore studied in SHR. Recordings of RBF autoregulation were done before and 30 min after intravenous infusion of the different drugs, and Pgc was thereafter measured with the stop-flow technique. When the mean arterial pressure (MAP) was reduced to approximately 120 mmHg by infusions of doxazosin or enalapril, the lower pressure limit of RBF autoregulation was reduced significantly. Nifedipine or verapamil abolished RBF autoregulation. Doxazosin did not change Pgc (43.6 +/- 1.4 vs. 46.7 +/- 1.5 mmHg in controls, P > 0.5), enalapril lowered (41.3 +/- 0.8 mmHg, P < 0.01), and the calcium channel antagonists increased Pgc [53.7 +/- 1.4 mmHg (nifedipine) and 54.8 +/- 1.2 mmHg (verapamil), P < 0.01]. When MAP was reduced to approximately 85 mmHg by drugs, Pgc was reduced to 43.3 +/- 1.7 mmHg after nifedipine (P > 0.2 vs. control), whereas Pgc after enalapril was 38.5 +/- 0.5 mmHg (P < 0.05 vs. control). Enalapril reduced Pgc mainly by reducing efferent resistance. During treatment with calcium channel antagonists, Pgc became strictly dependent on MAP. Monotherapy with nifedipine may increase Pgc and by this mechanism accelerate glomerulosclerosis if a strict blood pressure control is not obtained.

Resetting of renal blood autoregulation during acute blood pressure reduction in hypertensive rats

Decrease in systemic blood pressure, duration of pressure decrease, and change in the activity of the renin or the sympathetic nervous system may represent mechanisms involved in resetting the renal blood flow (RBF) autoregulation found in hypertensive rats. Autoregulation of RBF, plasma renin concentration (PRC), and the time needed for resetting to take place were studied in the nonclipped kidney before and after removal of the clipped kidney of two- kidney, one-clip (2K1C) hypertensive rats and before and after mechanical reduction of the renal arterial pressure (RAP) for 10 min in the spontaneously hypertensive rat (SHR) and in the nonclipped kidney of 2K1C hypertensive rats with and without renal denervation. Mean arterial pressure (MAP) fell from 147 to 107 mmHg 30 min after removal of the clipped kidney, and the lower pressure limit of RBF autoregulation decreased from 113 to 90 mmHg (P < 0.01); PRC fell. Mechanical reductions of RAP from 161 to 120 mmHg in the nonclipped kidney for 10 min did not change RBF, but at 120 mmHg, the lower pressure limit of RBF autoregulation was reduced from 115 mmHg before pressure reduction to 96 mmHg afterwards (P < 0.02). In SHR, similar pressure reduction for 10 min decreased the lower pressure limit of RBF autoregulation from 106 to 86 mmHg (P < 0.01). PRC was unchanged in both models, and denervation did not change RBF autoregulation. When RAP was reduced below the lower pressure limit of RBF autoregulation, RBF decreased approximately 20%; the lower pressure limit of RBF autoregulation remained unchanged. In normotensive Wistar-Kyoto rats, pressure reduction did not change the range of RBF autoregulation. These results indicate that acute normalization of the pressure range of RBF autoregulation in hypertensive rats is dependent on the degree of pressure reduction of RAP, whereas renal innervation and PRC do not play a major role. We propose that the mechanism of resetting is due to afterstretch of noncontractile elements of the vessel wall or is caused by pure myogenic mechanisms. An effect of intrarenal angiotensin cannot be excluded.

ANG II and vasopressin stimulate calcium entry in dispersed smooth muscle cells of preglomerular arterioles

Calcium signaling mechanisms were examined in vessel segments and dispersed single smooth muscle cells (SMC) of interlobular arteries and afferent arterioles (< 50 microns diameter) from the rat kidney. These resistance vessels were isolated from rat kidneys, using an iron oxide-sieving technique with subsequent collagenase digestion. Individual cells were identified by their characteristic oval appearance and positive staining for smooth muscle-specific alpha-actin and heavy chain myosin SM-1 and SM-2. Cytosolic calcium concentration ([Ca2+]i) was measured using fura 2 ratiometric fluorescence at 340 and 380 nm wavelength with a microscope-based photometer. Angiotensin II (ANG II) and arginine vasopressin (AVP), at concentrations of 10(-10)-10(-6) M, produced dose-dependent increases in [Ca2+]i; maximum increases were 221 +/- 49 nM for ANG II and 237 +/- 49 nM for AVP. The temporal response patterns for both agonists were characterized by a square-shaped, immediate step increase in [Ca2+]i to a near maximum level that was maintained through the recording period of 150-200 s. Responses of individual dispersed SMC and short vessel segments were similar. Losartan antagonized the action of ANG II, indicating mediation by AT1 receptors on preglomerular arteriolar SMC. The V1-selective antagonist [d(CH2)5Tyr(Me)2Tyr(NH2)9]AVP completely inhibited AVP-induced [Ca2+]i changes. The importance of calcium entry in hormone-induced changes in [Ca2+]i was demonstrated by the finding that neither ANG II nor AVP elicited a [Ca2+]i response in media rendered nominally calcium free by addition of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. Calcium entry occurred primarily through L-type, voltage-gated calcium channels as the dihydropyridine, nifedipine, completely prevented or reversed [Ca2+]i changes normally elicited by either hormone. Our results provide new information about the similarity of calcium signaling in single SMC and short segments freshly isolated from renal interlobular arteries and afferent arterioles. The observations indicate that AT1 and V1 receptors are coupled to signal transduction pathways leading to rapid changes in [Ca2+]i. Calcium mobilization appears to play a minor to nonexistent role under the experimental conditions. The predominant mechanism involves calcium entry through dihydropyridine-sensitive, voltage-gated calcium channels in single SMC from these resistance vessels.

Increased glomerular capillary pressure and size mediate glomerulosclerosis in SHR juxtamedullary cortex

To gain insight into the mechanisms in the development of glomerulosclerosis in juxtamedullary cortex, the degree of glomerulosclerosis, glomerular tuft diameter, glomerular capillary pressure (Pgc), and local renal blood flow (RBF) autoregulation were measured in superficial and juxtamedullary cortex of 10- and 70-wk-old spontaneously hypertensive rat (SHR), using aged matched Wistar-Kyoto (WKY) rats as controls. Pgc was measured after corticotomy by direct micropuncture of glomeruli in superficial and juxtamedullary cortex. Total RBF was measured by a transit-time flowmeter (Transonic) and local blood flow by use of laser-Doppler flowmetry. The degree of glomerulosclerosis measured by a semiquantitative histological technique was significantly increased in juxtamedullary compared with superficial cortex in all groups. The difference was most pronounced in the juxtamedullary cortex of 70-wk-old SHR. Pgc was significantly increased in juxtamedullary cortex compared with superficial cortex in 70-wk SHR (57.1 +/- 2.7 vs. 46.5 +/- 0.5 mmHg, P < 0.01). The corresponding data set from 70-wk WKY was 45.5 +/- 0.43 vs. 41.6 +/- 1.5 (P < 0.05). The Pgc in juxtamedullary cortex of 10-wk SHR was slightly higher than in superficial cortex (45.1 +/- 2.3 vs. 50.1 +/- 1.2 mmHg, P = 0.05), whereas there was no difference in 10-wk WKY. Glomerular diameter was larger in juxtamedullary cortex in old animals but not significantly different in 10-wk WKY rats and 10-wk SHR. Total RBF was reset to higher perfusion pressures in hypertensive rats. Juxtamedullary and superficial blood flow autoregulation were not significantly different from total RBF autoregulation in all groups. These results suggest that hypertrophy as well as increased Pgc might contribute to the development of manifest glomerulosclerosis. Changes in local blood flow autoregulation do not seem to play a major role in the development of glomerulosclerosis.

Acute effects of angiotensin II receptor antagonist on autoregulation of zonal glomerular filtration rate in renovascular hypertensive rats

This study was designed to assess the renal capability to autoregulate total blood flow, glomerular filtration rate (GFR) and local GFR in outer, middle and inner cortical layers (OC, MC, IC) in the two-kidney, one-clip (2K-1C) renovascular hypertensive rat, with or without acute infusion of the angiotensin II receptor antagonist losartan (5 mg/kg, i.v.). Age-matched, sham-operated Wistar rats were used as controls. The hemodynamic study in all animals was performed 4 weeks after clipping. The clipping increased blood pressure significantly, whereas losartan reduced the renal arterial pressure (RAP) from 165+/-8 to 125+/-6 mm Hg (p < 0.01) in 2K-1C hypertensive rats and reduced the RAP from 107+/-2 to 101+/-1 mm Hg (p < 0.05) in normotensive animals. Renal blood flow (RBF), total and local GFR were decreased in the nonclipped kidney of 2K-1C hypertensive rats compared with sham-operated rats, but losartan significantly increased the RBF and GFR. RBF was well maintained in response to reduction in RAP in the nonclipped kidneys with and without losartan treatment. The capability of total GFR autoregulation was impaired in untreated 2K-1C hypertensive rats and losartan-treated sham-operated rats, whereas losartan completely abolished GFR autoregulation in the nonclipped kidney of 2K-1C hypertensive rats. Losartan impaired autoregulation of zonal GFR to the same extent in all three cortical layers of sham-operated rats, whereas in the nonclipped kidney of 2K-1C hypertensive rats losartan had a more pronounced effect on the superficial GFR autoregulation than in middle and inner cortex, indicating that angiotensin II plays a major role in regulating the GFR response to the acute changes of renal arterial pressure.

Autoregulation of total and zonal glomerular filtration rate in spontaneously hypertensive rats with mesangiolysis

In this study we tested the hypothesis that mesangial cells participate in autoregulation of the glomerular filtration rate (GFR) in normotensive and hypertensive rats. Mesangial cell lesions were induced by intravenous administration of antithymocyte (anti-Thy 1.1) antibodies in spontaneously hypertensive rats (SHR) and in Wistar-Kyoto rats (WKY). Normal murine serum was injected in control rats. Hemodynamic measurements were performed 24 h after the infusion of the anti-Thy 1.1 antibodies. Renal blood flow (RBF) was measured by a transit time flowmeter (Transonic) and the GFR was measured as the uptake of 125 iodine-labeled aprotinin ([125]I-Ap) by proximal tubular cells at the control renal arterial pressure and (131)I-Ap at a pressure reduction close to the lower pressure limit of RBF autoregulation. RBF was unaltered and the autoregulatory capability was maintained in SHR and WKY after mesangial cell lesions. Mesangiolysis significantly reduced the total GFR in normotensive, but not in hypertensive animals. The fractional compensation of the GFR was attenuated in the outer cortical layer (p<0.05) in normotensive WKY. In SHRs the fractional compensation of the GFR was impaired in all cortical layers after mesangiolysis, slightly more in the outer than in the inner cortex. We conclude that mesangial cells may contribute to the autoregulation of GFR in hypertensive rats, but to a lesser extent in normotensive rats.

Autoregulation of total and zonal glomerular filtration rate in spontaneously hypertensive rats during antihypertensive therapy

The effects of angiotensin II type 1 receptor antagonist (losartan), angiotensin 1-converting enzyme (ACE) inhibitor (enalapril), and calcium channel blocker (nifedipine) on autoregulation of total and zonal glomerular filtration rate (GFR) were studied in spontaneously hypertensive rats (SHRs), 10 and 40 weeks of age, and 10-week-old Wistar-Kyoto (WKY) rats. Untreated animals in each group served as controls. Renal blood flow (RBF) was measured by a transit-time flow probe (Transonic) on the left renal artery. Total and zonal GFR (outer, middle, and inner cortex) were estimated from tubular uptake of 125iodine-labeled aprotinin (125IAp) injected i.v. at control renal arterial pressure (RAP), and 131IAp injected at a RAP reduced to the lower limit of RBF autoregulation. Autoregulation of RBF was reset to higher pressure levels in untreated hypertensive rats. Enalapril normalized this resetting in 10-week-old SHRs, but not in aged SHRs 40 weeks. Losartan did not completely normalize this resetting in either 10-or 40-week-old SHRs, whereas nifedipine impaired RBF autoregulation in both WKYs and SHRs. A decreased autoregulatory compensation of GFR after pressure reduction was observed in losartan-treated 10-week-old SHRs and after all drug regimens in 40-week SHRs. GFR autoregulation in outer, middle, and inner cortex was impaired in losartan-treated 10-and 40-week-old SHRs. With all treatments, the autoregulation in 10- and 40-week-old SHRs was better preserved in the inner than in the outer cortex. The impaired autoregulation may indicate that a part of the dilatory capacity of preglomerular vessels has already been taken out by hypotensive treatment. Renal vascular abnormalities may have an additional effect.

[Critical shortage of personnel in nephrology. Assessment of causes of the crisis and suggestion for solution]

The heavier work load for qualified nephrologists in Norway over the last ten years is described and compared with the number of positions. The increase in the number of dialysis treatments, care of renal transplant patients and other tasks performed by qualified nephrologists is roughly doubled from 1985 to 1995. By contrast the number of employed qualified nephrologists to pursue the work has only increased by 20% over the same period. As of today there is a lack of capacity to educate new nephrologists to fill up forthcoming vacancies. When the actual need for nephrologists is taken into account, the discrepancy is much more serious and will become even more so over the next ten years if no immediate action is taken. We suggest the establishment of six new educational positions. Altogether, these six new positions will provide the capacity to educate a reasonable number of trained nephrologists to meet future challenges, to the benefit of patients.

[Treatment of hypertension in renal parenchymal diseases]

Hypertension is a common finding in patients with renal parenchymatous diseases. Development of hypertension causes increased proteinuria, decline in glomerular filtration rate and reduced life span in experimental models of glomerulonephritis. Hypertension has been shown to reduce glomerular filtration rate in man. It is therefore important to treat hypertension. The blood pressure should be reduced to about 140/80 mm Hg. Reduction of glomerular capillary pressure, inhibition of glomerular permeability, renal hypertrophy and inhibition of mesangial metabolism are the main mechanisms of renal protection during antihypertensive therapy. Autoregulation of the renal blood flow probably has an impact on these mechanisms. Impaired autoregulation is found in kidneys with low glomerular filtration rate and during treatment with calcium channel blockers. Alpha receptor blockers, angiotensin converting enzyme inhibitors (ACE-) and angiotensin II receptor blockers do not interfere with autoregulation. All types of antihypertensive drugs provide similar renal protection when the glomerular filtration rate is reduced. When calcium channel blockers are used in kidneys with normal or slightly reduced function, either blood pressure should be kept strictly at normal levels or these type of drugs should be combined with ACE inhibitors or angiotensin II receptor blockers.

Extended measurement of glomerular filtration rate and effective renal plasma flow in ambulatory patients

We describe a standardized clearance method over 5 h (one hour equilibration followed by eight consecutive 30 min clearance periods [period 2-9]) for the estimation of GFR (iothalamate I125) and ERPF (hippuran I131) during water diuresis in ambulatory and exercising patients. Four groups were examined. In group I (normal controls, n = 15) there were no significant changes in GFR, ERPF and FF (P > 0.10) during repeated clearance periods (mean of period 2-5 versus period 6-9). The reproducibility of the method was studied at a mean interval of 3.7 weeks in a group of patients with stable reduction of GFR (group II, n = 7). The values for GFR, ERPF, FF and RVR did not change significantly in this group, and correlated significantly between repeated studies (r = 0.81 to r = 0.99). In group III (untreated hypertensive patients with reduced GFR, n = 13) there was a time dependent 7.2% decrease in GFR (P < 0.05), significantly different from group I (P < 0.02), a 10.0% decrease in ERPF (P < 0.01) and no significant change in FF (P = 0.08) when the mean of period 2-5 was compared with the mean of period 6-9. In healthy controls (group IV, n = 8) light sustained bicycle exercise (25 W) induced a 7.1% decline in GFR (P < 0.01), 17.4% decline in ERPF (P < 0.001) and a 13.6% increase in FF (P < 0.001). We conclude that ambulatory measurements of GFR and RPF can be carried out over a period of 5 h with satisfactory precision and repeatability. Ambulatory hypertensive patients with moderately reduced GFR showed the same degree of time dependent downward drift of GFR and ERPF without exercise as was seen in healthy individuals during light exercise. Accordingly, in these groups single clearance periods imply a risk for under or overestimation of renal function, and time controls are necessary during clearance studies.

Autoregulation of zonal glomerular filtration rate and renal blood flow in spontaneously hypertensive rats

Autoregulation of total and zonal glomerular filtration rate (GFR) in outer, middle and inner cortex was estimated in spontaneously hypertensive rats (SHR), from the tubular uptake of 125I-labeled aprotinin (125I-Ap), injected at control renal arterial pressure (RAP), and 131I-Ap, injected at reduced RAP in left kidney. Normotensive Wistar-Kyoto (WKY) rats were used as controls. Renal blood flow (RBF) autoregulation was reset to higher pressure levels in SHR. When RAP was lowered close to the lower pressure limit of RBF autoregulation, total GFR was reduced to 89.5 +/- 3.1 and 88.1 +/- 3.3% of control in 10- and 40-wk WKY and to 87.7 +/- 2.3 and 88.0 +/- 2.2% in 10- and 40-wk SHR. In WKY, the fall of GFR in the three cortical layers was not different during RAP reduction. In 10- and 40-wk-old SHR, however, GFR fell significantly less in inner than in middle and outer cortex (P < 0.05). We conclude that autoregulation of GFR is most efficient in the inner cortex of SHR. In all animals, GFR was less well autoregulated than RBF.

[Estimation of body composition in patients on dialysis by means of near-infrared interaction ]

Malnutrition and low serum albumin values predict increased mortality in uremic patients. Infrared interactance represents a novel approach to the estimation of body composition. We have examined total body fat, body water and fat-free weight in our male haemodialysis (n = 24) and peritoneal dialysis (n = 17) patients. There were no differences between the groups in a cross-sectional study. A longitudinal study showed a significant increase of total body fat (%) in the peritoneal dialysis patients after five months (mean values +/- SEM) (from 19.8 +/- 2.3 to 22.6 +/- 2.4, p < 0.05), and a significant decrease of body water (%) (from 59.9 +/- 1.5 to 58.2 +/- 1.6, p < 0.05). The difference in total body fat between the haemodialysis (n = 14) and peritoneal dialysis (n = 10) groups reached statistical significance (16.5 +/- 1.7 versus 22.6 +/- 2.4, p < 0.05). No difference was found in serum albumin. Infrared interactance has the capacity to characterize time-dependent differential changes of body composition in various dialysis modalities. Further studies are needed to describe the validity of the method for identification of patients with increasing malnutrition.

[Ultrasonographic evaluation of fat and muscles in patients on dialysis]

Malnutrition, shown by fat depletion and muscle wasting, is common in uremia. The methods used to describe body composition in uremia are controversial. We have used ultrasonography of the thigh to evaluate fat and muscle in haemodialysis patients (group 1) (n = 14), peritoneal dialysis patients (group 2) (n = 10) and normal controls (group 3) (n = 13). Musculus rectus femoris diameter (0.84 +/- 0.06 cm versus 1.15 +/- 0.08 cm, p < 0.05) and cross sectional area (3.0 +/- 0.4 cm2 versus 5.5 +/- 0.4 cm2, p < 0.01) were significantly reduced in group 1 compared with group 3, as was also muscle area in group 2 (3.9 +/- 0.6, p < 0.05), indicating malnutrition in the dialysis patients. Peritoneal dialysis patients tended to have more subcutaneous fat (p = 0.07) and a larger musculus rectus diameter (p = 0.09) than haemodialysis patients, possibly reflecting better preserved nutritional status. Ultrasonography was equal to computed tomography for estimating these parameters. Ultrasonography is a useful tool for evaluating body composition in uremia, and has a capacity for detection of malnutrition, and possibly for early discrimination between patient groups with different dialysis modalities.

[Alpha blockaders--first or second line antihypertensive agents?]

Alpha-receptor blockers reduce blood pressure by blocking of the alpha 1-receptors in the smooth muscle cells in the arteriolar walls. The heart pump function is not disturbed. Most studies have shown that the alpha-receptor blockers induce a reduction in plasma-triglycerides and an increase in the ratio between HDL- and LDL-cholesterol. They do not interfere with the metabolism of electrolytes, glucose or uric acid and have no negative effect on pulmonary function. Although long-term use does not induce a permanent increase in heart rate, some patients respond to initial therapy with faster heart rate and palpitations. The alpha-receptor blockers should not be used in patients with coronary heart disease if the patient is not on chronic beta-blockade. When these precautions are followed, the alpha-blockers can be used as first-line treatment--just like ACE-inhibitors and calcium-antagonists.