Extrarenal resistance to atrial natriuretic peptide in rats with experimental nephrotic syndrome

Nephrotic syndrome is associated with resistance to the renal actions of atrial natriuretic peptide (ANP). We performed experiments in anesthetized, acutely nephrectomized rats 21-28 days after injection of adriamycin (7-8 mg/kg i.v.) or 9-14 days after injection of anti-Fx1A antiserum (5 ml/kg i.p.) (passive Heymann nephritis; PHN) to test whether extrarenal resistance also occurred. Proteinuria was significantly elevated in both models compared with controls before study. ANP infusion (1 microgram.kg-1.min-1) caused arterial pressure to decrease similarly in control rats, adriamycin-treated rats, and rats with PHN (by 8.2 +/- 1.0, 9.4 +/- 2.3, and 9.0 +/- 2.0%, respectively; all P < 0.05 vs. both baseline and vehicle-infused control rats). In control rats, hematocrit increased progressively to a maximal value 9.5 +/- 0.9% over baseline as a result of the infusion, an increase corresponding to a reduction in plasma volume of 16.1 +/- 0.9%. The ANP-induced increase in hematocrit was preserved in adriamycin-treated rats (9.2 +/- 1.3%) but was markedly blunted in rats with PHN (2.4 +/- 1.3%; P < 0.0001 vs. ANP infusion in control rats). ANP infusion increased plasma ANP levels to the same extent in the three groups, whereas plasma guanosine 3',5'-cyclic monophosphate was significantly lower in rats with PHN compared with both control and adriamycin-treated rats. Infusion of a subpressor dose of angiotensin II (ANG II, 2.5 ng.kg-1.min-1) fully restored the ANP-induced increase in hematocrit in rats with PHN. This study demonstrates that 1) the hemoconcentrating and hypotensive actions of ANP are preserved in adriamycin-treated rats, 2) the effect of ANP on hematocrit and fluid distribution is blunted in rats with PHN while its hypotensive action is preserved, and 3) low-level ANG II infusion normalizes the hemoconcentrating effect of exogenously infused ANP in rats with PHN. Thus deficient ANG II generation in rats with PHN, but not adriamycin nephrosis, may contribute to extrarenal ANP resistance.

Role of angiotensin in renal sympathetic activation in nephrotic syndrome

The effect of type 1 angiotensin II receptor antagonist treatment (losartan) on cardiac baroreflex regulation of renal sympathetic nerve activity (RSNA) and renal sodium handling in rats with nephrotic syndrome was examined. After intravenous losartan administration, with arterial pressure normalized by intravenous methoxamine, basal RSNA was decreased 14 +/- 3% in arterial baroreceptor-intact rats and by 21 +/- 5% in arterial baroreceptor-denervated rats. Intracerebroventricular losartan, which did not affect arterial pressure, decreased basal RSNA activity by 15 +/- 1%. Both intravenous and intracerebroventricular losartan augmented the renal sympathoinhibitory response to acute volume loading, and this was associated with an enhanced natriuretic response to the acute volume load. In nephrotic syndrome, acute losartan administration improved cardiac baroreflex regulation of RSNA, which was associated with improved ability to excrete acute sodium loads.

A case of deep vein thrombosis in idiopathic nephrotic syndrome with resistance to activated protein C

We report a case of deep vein thrombosis in a young man with idiopathic nephrotic syndrome and resistance to activated protein C. We postulate that patients with concurrent nephrotic syndrome and factor V may have an increased risk of thrombosis. Screening for factor V Leiden may be indicated in patients with idiopathic nephrotic syndrome.

Effect of postural change on urine volume and urinary sodium excretion in diabetic nephropathy

Fluid retention develops relatively early in the renal insufficiency of patients with diabetic nephropathy. The objective of this study was to clarify the effect of postural change on urine volume and urinary sodium excretion in diabetic nephropathy. Subjects consisted of 16 patients with non-insulin-dependent diabetes mellitus (five with diabetic nephrotic syndrome [DNS], five with nonnephrotic overt diabetic nephropathy [NNODN], and six without overt diabetic nephropathy [ODN]) and 11 patients with nondiabetic renal diseases (five with nondiabetic nephrotic syndrome [NDNS] and six without nephrotic syndrome). Patients were studied during 60 minutes of recumbency, followed by 60 minutes of standing. Mean blood pressure decreased in the standing posture only in patients with DNS and nondiabetic renal diseases. Urine volume decreased in the standing posture in the three groups of diabetic patients. Urine volume showed no changes in the standing posture in nondiabetic patients with and without nephrotic syndrome. The decreases in mean blood pressure and urine volume and the percentage decrease in creatinine clearance were significantly larger in patients with DNS than in those with NDNS and NNODN. The increase in free water clearance was significantly smaller in patients with DNS than in those with NDNS and NNODN. Urinary sodium excretion decreased in the standing posture in diabetic and nondiabetic patients, while no differences in the magnitude of changes were noted among patients with NDNS, NNODN, and DNS. It is concluded that the standing posture causes a greater decrease in urine volume due to orthostatic hypotension in patients with DNS compared with those with NDNS and NNODN, and that the presence of orthostatic hypotension in patients with DNS is likely responsible for the greater fluid retention of this group compared with other nephrotic patients with similar degrees of hypoalbuminemia.

Glomerular atherosclerosis

This paper suggests a two-hit model for lipoprotein-mediated progressive renal disease, in which postsecretory modification of low-density lipoprotein may favour the transformation of mesangial cells, monocytes and macrophages to glomerular foam cells. Proteinuria and lipiduria would mediate tubulointerstitial damage. Based on this, careful treatment with lipid-lowering agents, lipopheresis and antioxidants may ameliorate the progression of glomerular and tubulointerstitial pathology.

Progression of renal failure: role of apolipoprotein B-containing lipoproteins

Plasma lipoproteins (LP) may be identified on the basis of density properties or apolipoprotein (apo) composition. ApoB-containing LP occur in VLDL, IDL and LDL. There are several types of apoB-containing LP characterized by specific composition of minor apolipoproteins (apoC, apoE etc.) and lipid constituents (triglycerides and cholesterol), metabolic properties and relative atherogenicity. The alterations of lipoprotein metabolism in renal disease resulting in elevated levels of apoB-containing LP may be reflected in hyperlipidemia. Whereas nephrotic syndrome and heavy proteinuria are associated with increased formation of cholesterol-rich apoB-containing LP in LDL and VLDL, the characteristic feature in renal failure is the accumulation of intact or partially metabolised triglyceride-rich LP in IDL and VLDL. The potentially atherogenic apoB-containing LP have been linked to the pathogenic processes that result in progressive glomerular and interstitial lesions and ultimate loss of renal function. The mechanisms of injury are not fully understood. Receptor- and non-receptor mediated uptake of LP by mesangial cells may induce or accelerate proliferative and sclerotic processes in the glomerular mesangium that are analogous to atherosclerosis in the arterial wall. Changes in glomerular permeability can result in increased filtration of LP that may be internalized by tubular cells and elicit corresponding lesions in the interstitial tissues. The negative impact of proteinuria on the prognosis of renal disease could be mediated in part through an increased filtration of lipoproteins. Induction of hyperlipidemia accelerates glomerular and interstitial damage in experimental renal failure. This can be attenuated by treatment with hypolipemic agents. In patients, increased concentrations of apoB-containing LP are associated with more rapid progression of renal insufficiency in both primary renal disease and diabetic nephropathy. It is, however, presently not known to what extent treatment of the renal dyslipidemia can modify the progression of chronic renal failure. Experimental and clinical evidence suggest that apoB-containing LP may play a pathogenetic role in the progression of renal disease.

Tuberculosis in childhood nephrotic syndrome in India

We studied the prevalence, clinical features, and impact of tuberculosis (TB) on children with nephrotic syndrome (NS). Of the 300 children with NS, 28 (9.3%) were diagnosed as having TB. This occurred following the initiation of immunosuppressive therapy in 27 children, and in 1 child it preceded the onset of NS. Pulmonary involvement was the commonest (22/28), followed by tubercular lymphadenitis (2/28), meningitis (2/28), and occult TB (2/28). Of the various diagnostic criteria, history of previous cough, fever, or exposure to a case of TB (23/28) and chest skiagram (21/28) were the most useful. The occurrence of TB did not induce a relapse or affect the subsequent response to steroid therapy (as is often seen with other infections) or have a deleterious effect on renal function. Patients who received higher doses of steroids (frequent relapsers, steroid dependent, initial non-responders, and subsequent non-responders) had a significantly higher prevalence of TB (19/148) than those who received lower doses (infrequent relapsers 8/151) (P = 0.04). We thus found TB to be an important complication of children with NS in our country. The conventional diagnostic tests, such as Mantoux and acid-fast bacilli isolation, are often unhelpful in these children, and a high index of suspicion is required, especially in children who require frequent courses of steroid therapy.

Reversible glomerular hypertrophy in adult patients with primary focal segmental glomerulosclerosis

The present study was performed to assess the pathogenetic role of glomerular hypertrophy in patients with primary focal segmental glomerulosclerosis (FSGS). We studied 14 patients with FSGS by morphometry. In seven patients, minimal change nephrotic syndrome (MCNS) was diagnosed on the first renal biopsy, but FSGS was diagnosed on the second biopsy (MCNS-FSGS group). Seven other patients with FSGS on the first biopsy underwent second biopsies while in remission (FSGS-R group). Biopsy results were compared with biopsies from 10 patients with MCNS and seven control subjects. Nonsclerotic glomeruli were examined. The mean glomerular tuft area, whole glomerular area, and number of mesangial cells were significantly increased in both biopsies from the MCNS-FSGS group and in the first biopsies obtained during the nephrotic stage of the FSGS-R group, compared with control subjects and patients with MCNS. Biopsies from FSGS patients in remission showed that the mean glomerular tuft area and number of mesangial cells were significantly decreased. The fractional extracellular matrix area (extracellular matrix area/glomerular tuft area) and mesangial cell density (mesangial cell number/glomerular tuft area) in FSGS during both nephrotic and remission stages were the same as those in control subjects and patients with MCNS. The present study suggests that glomerular hypertrophy precedes the development of glomerulosclerosis in FSGS and is reversible when patients are in remission. These features support the pathogenetic importance of glomerular hypertrophy in patients with primary FSGS.

Transient alteration of the reproductive function in nephrotic rats

The reproductive function of male and female rats with induced nephrotic syndrome was examined by assessing hormonal levels, the estrous cycle pattern and fertility. Measurements were carried out on day 10 (nephrotic stage) and on day 30 (remission stage) after treatment (a single s.c. dose of puromycin aminonucleoside 15 mg/100 g body wt.). Serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and progesterone (P4) from both sexes as well as 17beta-estradiol (E2) in females and total testosterone (tT) in males were assayed at both phases of the illness by specific radioimmunoassays; free and urine testosterone (fT, uT) was also determined in male rats on day 10. The estrous cycle was followed alongside the study through vaginal smears, while fertility was estimated by the rate of pregnancies (females) or pregnancy induction (males), and by the litter size. The results showed that most serum hormone levels, except FSH in females, were significantly reduced at the nephrotic stage of the illness, returning to their normal values after 30 days. Besides, on day 10, fT was found reduced in nephrotic males, while uT concentrations remained unmodified. The ovulatory cycle of nephrotic rats was disrupted on day 3 and not restored until day 23; nevertheless, the reproductive function, measured as a fertility index, was fully reinstalled at the remission stage. Interestingly, the capacity of fertilization of the nephrotic males was not entirely abolished during the acute phase, since 37% of the animals were fertile. Moreover, on day 30 the reproductive function in nephrotic males was totally recovered. The data from this study show the existence of reversible endocrine disorders in rats bearing nephrotic syndrome; such changes are manifested during the acute phase of the illness as a temporary cessation of the reproductive processes.

Single- versus divided-dose prednisolone therapy for relapses of nephrotic syndrome

Relapses of nephrotic syndrome are usually treated with prednisolone, initially in three to four daily divided doses. The divided-dose regimen may cause poor patient compliance and greater adrenal suppression. In a prospective randomized controlled trial, we compared the efficacy of prednisolone in inducing remission of nephrotic syndrome, when given either as a single dose or in divided doses. Patients with steroid-responsive nephrotic syndrome with relapse were randomized to receive prednisolone 2 mg/kg per day, either as a single morning dose or in three divided doses for 2 weeks, followed by 1.5 mg/kg on every alternate day for 4 weeks. Parents tested the urine for protein daily until remission (nil proteinuria for 3 consecutive days). The duration between initiation of treatment and achievement of remission was recorded. Of 106 patients, 94 (47 each in single-dose and divided-dose groups) completed the study. The patients in the two groups were similar in relation to age, sex, number of relapses in the preceding year, and blood levels of creatinine, albumin, and cholesterol. The mean time for achievement of remission in the single- and divided-dose groups was 8.6 and 8.5 days, respectively (P = 0.94, power 96%). After 9 months' follow-up, there were no differences in the frequency of relapses and cumulative dose of prednisolone received in the two groups. The observations suggest that prednisolone administered in a single daily dose or in divided doses is equally effective in inducing remission in patients with relapsing nephrotic syndrome.

A case of nephrotic syndrome with rapid spontaneous remission in an elderly patient

In July 1994, a 70-year-old woman was diagnosed as having nephrotic syndrome with proteinuria of 8 to 10 g/day and a serum albumin level of 1.8 g/dl. She was hospitalized in August 1994 for investigation. The urinary findings then normalized, with urinary protein and occult blood both negative and total urinary protein excretion at 0 g/day. A renal biopsy was performed, and spontaneous remission of minimal change nephrotic syndrome was diagnosed. This is an interesting case involving rapid remission of minimal change nephrotic syndrome in an elderly patient.

Reflex influences on renal nerve activity characteristics in nephrosis and heart failure

Cardiac baroreflex regulation of efferent renal sympathetic nerve activity (ERSNA) is abnormal in nephrotic syndrome (NS). The purpose of the present study was to examine the responses of amplitude and frequency of synchronized ERSNA discharge in anesthetized NS rats subjected to reflex maneuvers that alter the activity of and the interaction between aortic and cardiac baroreceptors. Steady-state ERSNA was analyzed in three groups of anesthetized rats: control, NS, and congestive heart failure (CHF) (in the latter, the defect in cardiac baroreflex regulation of ERSNA is peripheral rather than central). In protocol A, analysis was performed during control, after bilateral aortic depressor nerve section, after bilateral cervical vagus nerve section, and during central vagus nerve stimulation (VAGSTIM). In protocol B, analysis was performed during control, after bilateral cervical vagus nerve section, after bilateral aortic depressor nerve section, and during central aortic depressor nerve stimulation. In protocol A, VAGSTIM decreased ERSNA and peak height (fewer active fibers), but not peak frequency, in control and CHF but not NS rats. In NS rats, this lack of effect of VAGSTIM was specific for ERSNA, because depressor and bradycardia responses to VAGSTIM were unaffected. In protocol B, central aortic depressor nerve stimulation decreased ERSNA and peak height, but not peak frequency, in control, CHF, and NS rats similarly. It is concluded that the defect in cardiac baroreflex function in NS is specific for ERSNA, is central rather than peripheral, and affects the number of active renal sympathetic nerve fibers rather than their firing frequency.

Podocyte alpha-actinin induction precedes foot process effacement in experimental nephrotic syndrome

Attachment of podocytes to the glomerular basement membrane is thought to be mediated primarily by alpha 3/beta 1-integrins and by cytoskeletal proteins including actin, talin, vinculin, and alpha-actinin. We analyzed the expression of those molecules in rat glomeruli at several time points during induction of podocyte foot process effacement and nephrotic syndrome with puromycin aminonucleoside (PAN). PAN injection resulted in marked induction of glomerular alpha-actinin (40% increase vs. paired controls, P < 0.01), which clearly preceded development of podocyte foot process effacement and proteinuria and localized almost exclusively to podocytes. Delayed induction of glomerular alpha 3-integrin (44% increase vs. paired controls, P < 0.01) following foot process effacement was also observed but was not restricted to podocytes. No significant changes in glomerular vinculin, talin, beta 1-integrin, or total actin expression occurred at any time point during disease development. We conclude that foot process effacement is preceded by induction of alpha-actinin in podocytes in experimental nephrotic syndrome. Altered expression of this actin cross-linking protein in podocytes may have a pathogenic role in foot process effacement in nephrotic syndrome.

Inaccuracy of the Schwartz formula in estimating glomerular filtration rate in Nigerian children

The accurate estimation of renal function is of vital importance in the management of a child with renal disease. Given the well known difficulties of obtaining an accurately timed 24-hour urine sample from children and lacking the resources for estimating glomerular filtration rate (GFR) using radionuclide methods, the clinician practising in a developing country often has to resort to the use of height/plasma creatinine formulae when a rapid assessment of GFR is needed. In order to assess the accuracy of one of the better known formulae (Schwartz formula) in predicting GFR, 34 children with the nephrotic syndrome and 30 apparently healthy children with no evidence of renal disease were studied at the University College Hospital, Ibadan. Two methods, Altman-Bland analysis and correlation coefficients, were used to assess agreement between measured GFR (by endogenous creatinine clearance) and GFR estimated by formula. The results show that the height/plasma creatinine formula of Schwartz et al. is a poor predictor of GFR as measured by endogenous creatinine clearance in Nigerian children and that it overestimated GFR in over two-thirds of the children. These observations may be due to differences in the constant, k, in the formula, which was found to vary widely in this study with a mean value of 0.45 compared with 0.55 in the formula. It is suggested that height/creatinine formulae for predicting GFR be tested and validated for accuracy in a given environment before routine use in clinical settings.

[Effects of cyclosporin A on the diurnal variation of blood pressure in patients with nephrotic syndrome]

We investigated the hemodynamic, renal, and hormonal effects of cyclosporin A (CyA) treatment (6 mg/kg per day) for 4 weeks in 12 patients with nephrotic syndrome (8 women: 4 men, aged 36-66 years, 3 cases of focal glomerular sclerosis: 9 cases of membranous nephropathy). To evaluate the effects of CyA on the diurnal variation of blood pressure (BP), 24-h non-invasive BP monitoring was performed using model ABPM-630 (Nihon Colin, Tokyo, Japan) before and during CyA treatment. As indices of hemodynamics, intra-arterial pressure was monitored and cardiac output was measured by the dye-dilution technique using a cuvette at 0 and 4 weeks after treatment. CyA ameliorated urinary protein excretion and hypoproteinemia from 3.5 +/- 0.9 to 2.2 +/- 0.7 g/day, and serum protein concentration from 4.9 +/- 0.2 to 5.5 +/- 0.2 g/dl after 4 weeks' treatment. Endogenous creatinine clearance, 24-h urinary sodium excretion, and plasma renin activity decreased significantly at 1 week. CyA treatment raised casual BP from 122 +/- 4/75 +/- 2 to 140 +/- 5/87 +/- 3 mmHg after 1 week and to 146 +/- 4/90 +/- 2 mmHg after 4 weeks. Before treatment 24-h ambulatory BP monitoring showed BP reduction at night (116 +/- 5/68 +/- 3 mmHg) compared to the daytime (124 +/- 5/75 +/- 2 mmHg). The diurnal variation of BP disappeared during CyA treatment; mean daytime and nighttime pressures were 135 +/- 4/81 +/- 2, 132 +/- 5/80 +/- 3 mmHg at 1 week and 139 +/- 5/83 +/- 3, 131 +/- 6/80 +/- 3 mmHg at 4 weeks, respectively. On hemodynamic study; a 4-week treatment with CyA increased mean arterial pressure from 91 +/- 3 to 104 +/- 3 mmHg, total peripheral resistance index from 2.1 +/- 0.1 to 2.5 +/- 0.1 x 10(3) dyne.sec.cm-5.m2, and unchanged heart rate and cardiac index. Serum Mg concentration decreased from 2.1 +/- 0.1 to 1.7 +/- 0.1 mg/dl. These results suggest that CyA-induced hypertension is characterized by the loss of nocturnal decline in blood pressure, which is accompanied by volume retention after 1 week and systemic vasoconstriction after 4 weeks.

Prognostic significance of the early course of minimal change nephrotic syndrome: report of the International Study of Kidney Disease in Children

The ability to predict the course in children with newly diagnosed minimal change nephrotic syndrome (MCNS) may have significant therapeutic implications. Previous attempts based on data available at disease onset have not been successful. Therefore, it was investigated whether characterization of the initial response to adrenocortical steroids and the course during the early months of disease are predictive of the subsequent outcome. Three hundred-eighty-nine children with MCNS, diagnosed at onset, were treated with standard prednisone regimens and monitored for up to 17 yr (mean, 9.4 yr). They were classified, after 8 wk of therapy, as initial responders (complete remission) or initial nonresponders (continued proteinuria). Subsequent classifications included nonrelapsers, infrequent relapsers, and frequent relapsers. At 8 yr of follow-up, 80% of patients were in remission. Three-fourths of initial responders who remained in remission during the first 6-month period after initial therapy (nonrelapsers; 40% of the entire series) either continued in remission during their entire course or relapsed rarely. In contrast, initial relapsers, both frequent and infrequent, achieved a nonrelapsing course only after an average of 3 yr. Unremitting proteinuria during the initial 8 wk of treatment was followed by progression to ESRD in 21%. When proteinuria during the initial 8 wk continued through the subsequent 6 months, progression to renal failure occurred for 35%. Although 95% of children with MCNS do well, 4 to 5% die from complications or undergo progression to ESRD. Documentation of the early course aids in identifying those at increased risk for a poor outcome. More aggressive therapy may be indicated for these individuals.

Diagnosis and management of glomerular diseases

Glomerular diseases are a diagnostic challenge. Early recognition and timely institution of appropriate treatment are critical to optimum outcome in many patients, especially those with rapidly progressive glomerulonephritis. The clinical presentations and laboratory data provide adequate presumptive diagnoses in some patients; however, renal biopsy evaluation is often required for a definitive diagnosis.

Treatment of the idiopathic nephrotic syndrome: regimens and outcomes in children and adults

This review compares the biopsy patterns, complications, responses to therapy, and long-term outcomes of idiopathic NS in children and adults. On first examination, distinctions between the pediatric and adult diseases seem more quantitative than absolute. However, underlying determinants of outcome, including immunocompetence, growth, maturity, and senescence, can present very different challenges for pediatricians and internists. The major biopsy patterns in pediatric NS include MCD, FSGS, and DMP. MCD is overwhelmingly the most frequent and most steroid-responsive of the three but commonly presents problems of massive edema, serious bacterial infections, and multiple relapses. Because of the prompt response of pediatric MCD to corticosteroids, steroid resistance in children has generally been defined as persistence of proteinuria after 1 month of daily followed by 1 month of intermittent prednisone administration. By this criterion, nephrotic FSGS is usually steroid-resistant and, if not controlled by more aggressive therapy, typically progresses to ESRD. DMP is commonly steroid-resistant but may slowly resolve. It is not clear to what extent remissions of DMP represent a delayed response to steroids or would have occurred without treatment. Biopsies showing a few globally obsolescent glomeruli or mild mesangial hypercellularity may be associated with greater difficulty in management but have been included in the broad category of MCD. Moreover, evolution of patterns in serial biopsies, variable steroid-responsiveness of FSGS and DMP, and progression of some cases of MCD to ESRD suggest common features in the three major categories. Among adults with idiopathic NS, FSGS is the most frequent biopsy pattern, followed by MN (which is rare in children) and then by MCD. In contrast to its pediatric counterpart, MCD in adults is less regularly and more slowly responsive to corticosteroids and in the elderly is more commonly associated with hypertension and renal failure. MCD in adults is less likely to relapse once remission is achieved. Adults with FSGS present less commonly with severe edema than do children with this lesion. Although children and adults with FSGS present similar challenges of resistance to therapy and loss of renal function, the more aggressive oral steroid regimens used by internists preclude strict comparisons between pediatric and adult series. There is insufficient information to support a systematic analysis of DMP in adults. Cytotoxic agents and cyclosporine have been used with varying success in children and adults with difficult cases of NS. In MCD, an alkylating agent can increase the likelihood and duration of remission. Cyclosporine can also improve control in MCD, but continued treatment is often needed to maintain remission. Significant control of steroid-resistant FSGS has not been achieved with limited courses of an alkylating agent or cyclosporine. Longer courses of either of these immunosuppressants, especially when combined with intermittent steroid administration, can produce more complete and/or more sustained remissions. However, cyclosporine nephrotoxicity is more severe in FSGS than in MCD and in steroid-resistant than in steroid-dependent NS, regardless of biopsy pattern. A protocol combining iv M-P pulses, alternate-day prednisone, and an alkylating agent in steroid-resistant pediatric FSGS has produced the highest percentage of sustained remissions with normal renal function, of all reported regimens. Controlled trials of this and other combined drug protocols are needed in children and adults.

Regulation of hepatic angiotensinogen gene expression in nephrotic rats

Plasma angiotensinogen (Ao) concentration (PAC), urinary Ao excretion (UAE), hepatic levels of Ao mRNA and plasma renin concentration (PRC) were studied in control and nephrotic rats subjected to the following treatments: dexamethasone (DEX), ethinyl-estradiol (EE), tri-iodothyronine (T3), bilateral nephrectomy (NX), captopril (CAP) and adrenalectomy (ADX). In nephrotic rats PAC diminished, UAE and PRC augmented and Ao mRNA levels were not altered. In control rats, DEX, EE, T3 and NX increased PAC and Ao mRNA levels whereas CAP diminished PAC but not affected Ao mRNA. ADX diminished PAC and Ao mRNA levels. In nephrotic rats, these treatments produced the same effect than in control rats except in ADX which did not affect PAC. These data suggest that the decreased PAC is not related to alterations in hepatic Ao gene expression but to elevated PRC and UAE.

Regulation of renal sodium and water excretion in the nephrotic syndrome and cirrhosis of the liver

Atrial natriuretic peptide (ANP) produced in the heart and prostaglandin E2 (PGE2) synthesised in the kidneys facilitate renal excretion of sodium and water, and thus oppose the actions of angiotensin II, aldosterone, arginine vasopressin (AVP), endothelin, and the renal sympathetic nerves. In the present work we studied the contributions and interactions of these substances in the regulation of blood volume (BV), renal haemodynamics, renal sodium and water handling and blood pressure (BP) in patients with glomerulonephritis and cirrhosis. The aim was through a better understanding of the pathophysiology to improve the treatment of fluid retention in these patients, which occurs as development of the nephrotic syndrome and accumulation of ascites, respectively. Normotensive patients with glomerulonephritis but without the nephrotic syndrome had normal baseline BV values measured as the sum of plasma volume and red cell volume; they responded to BV expansion after infusion of albumin and BV depletion after administration of furosemide with appropriate counterregulatory hormonal changes. However, they tended to hold more fluid within the intravascular phase after both manipulations than did the healthy subjects. The acutely induced increase in BV did not affect the BP, which was likely attributable to the changes in plasma values of angiotensin II and ANP shown. ANP could be expected to be a tool in the management of fluid accumulation in patients with the nephrotic syndrome and cirrhosis. The non-renal effects of high-dose ANP were studied for the first time in dialysis patients without excretory kidney function. A reversible shift of fluid away from the intravascular phase was demonstrated. The BV was maximally reduced 30 min after ANP had been given. The BP was reduced before fluid displacement occurred and to the same extent in patients and healthy subjects. The reduction in the BV was negatively correlated to the reduction in BP. From that study it is inferred that the BP reducing effect of ANP is not mediated by its diuretic effect or ability to displace fluid from the intravascular to the interstitial fluid compartment. As a pharmacological dose of ANP was given, it can only be suggested that endogenous ANP, by altering transcapillary Starling mechanisms, assists in buffering intravascular fluid expansion until renal excretion or dialysis can take place. The same dose of ANP was given to patients with the nephrotic syndrome and cirrhosis. The ability of ANP to increase sodium excretion through inhibition of sodium reabsorption in the distal tubules and to increase the glomerular filtration rate (GFR) was blunted in both patient groups, but the BP was reduced to the same extent as in the healthy controls. Patients with the nephrotic syndrome tended to have a slightly elevated BP. We only studied patients with normal or slightly reduced GFR. They had a normal BV, reduced renal filtration fraction, suppressed aldosterone, increased ANP, but normal plasma values of angiotensin II, endothelin, and AVP, and normal urinary excretion of PGE2. Thus, neither haemodynamic nor hormonal factors can easily explain the spontaneous sodium retention or the resistance to the effects of ANP and furosemide. An interesting finding, not previously reported in nephrotic humans, was the low cyclic guanosine 3'5'-monophosphate (cGMP) in plasma and urine in relation to ANP, both before and after administration of ANP. It is hypothesised that renal resistance to ANP, exaggerated renal cGMP degradation, or preponderance of clearance receptors in nephrotic kidneys may contribute to sodium retention and the low filtration fraction. Elevation of ANP in these patients is connected with increased albuminuria, and probably an increase in intraglomerular capillary pressure. The resistance to furosemide could not be attributed to delayed passage of fluid from the interstitial to the intravascular fluid phase, but is most likely due to renal tubular resistan