Electrophoretic analysis of serum and urinary proteins in rats with aminonucleoside-induced nephrotic syndrome

A comparison of Tris-glycine and Tris-tricine buffers for the electrophoretic separation of major serum proteins

This paper compares different buffer systems for the electrophoretic separation of the five most abundant serum proteins on native-PAGE gel and cellulose membranes. A modified Tris-tricine system was shown to be superior for the separation of these serum proteins in a 7% m/v native-PAGE gel as compared with the traditionally used Tris-glycine and Tris-tricine methods. This modified Tris-tricine buffer system was also employed for the separation of serum proteins using a cellulose acetate membrane and very effective separation was observed as compared with the traditionally used Tris-barbital and Tris-glycine buffer systems.

Steroidogenic impairment due to reduced ovarian transcription of cytochrome P450 side-chain-cleavage (P450scc) and steroidogenic acute regulatory protein (StAR) during experimental nephrotic syndrome

The nephrotic syndrome is a renal disease characterized by proteinuria, hypoproteinemia, edema and hyperlipidemia. It has been reported that female nephrotic rats are characterized by loss of the oestrus cycle, follicle atresia, low gonadotropin and steroid concentrations; particularly, undetectable estradiol levels. Therefore, to determine the mechanisms involved in the ovarian steroidogenesis impairment, in this present study we evaluated the ovarian expression of the essential steroidogenesis components: cytochrome P450 side cholesterol chain cleavage enzyme (P450scc) and steroidogenic acute regulatory protein (StAR). The experiments were conducted in the rat experimental model of nephrosis induced by puromycin aminonucleoside (PAN) and in control groups. The evaluation of the expression of P450scc and StAR mRNA were performed during the acute phase of nephrosis as well as after the exogenous administration of 1 or 4 doses of human chorionic gonadotrophin (hCG), or a daily dose of FSH or FSH+hCG for 10 days. In addition, serum hormone concentrations, intra-ovarian steroid content, and the reproductive capacity were determined. The results revealed a decreased expression of mRNA of P450scc enzyme and StAR during nephrosis, and eventhough they increased after gonadotropins treatment, they did not conduce to a normal cycling rat period or fertility recovery. This study demonstrates that the mechanism by which ovarian steroid biosynthesis is altered during acute nephrosis involves damage at the P450scc and StAR mRNA synthesis and processing.

Soy protein diet ameliorates renal nitrotyrosine formation and chronic nephropathy induced by puromycin aminonucleoside

It has been shown that reactive oxygen species are involved in chronic puromycin aminonucleoside (PAN) induced nephrotic syndrome (NS) and that a 20% soy protein diet reduces renal damage in this experimental model. The purpose of the present work was to investigate if a 20% soy protein diet is able to modulate kidney nitrotyrosine formation and the activity of renal antioxidant enzymes (catalase, glutathione peroxidase, Cu,Zn- or Mn-superoxide dismutase) which could explain, at least in part, the protective effect of the soy protein diet in rats with chronic NS induced by PAN. Four groups of rats were studied: (1) Control rats fed 20% casein diet, (2) Nephrotic rats fed 20% casein diet, (3) Control rats fed 20% soy protein diet, and (4) Nephrotic rats fed 20% soy protein diet. Chronic NS was induced by repeated injections of PAN and rats were sacrificed at week nine. The soy protein diet ameliorated proteinuria, hypercholesterolemia, and the increase in serum creatinine and blood urea nitrogen observed in nephrotic rats fed 20% casein diet. Kidney nitrotyrosine formation increased in nephrotic rats fed 20% casein diet and this increase was ameliorated in nephrotic rats fed 20% soy protein diet. However, the soy protein diet was unable to modulate the antioxidant enzymes activities in control and nephrotic rats fed 20% soy protein diet. Food intake was similar in the two diet groups. The protective effect of a 20% soy protein diet on renal damage in chronic nephropathy induced by PAN was associated with the amelioration in the renal nitrotyrosine formation but not with the modulation of antioxidant enzymes.

Dynamic tests and FSH biological activity in female rats with acute nephrotic syndrome

To investigate the pituitary-ovarian status during the acute state of the nephrotic syndrome, a sequence of experiments were undertaken in adult female rats after a single dose of the puromycin aminonucleoside (PAN). The functional condition of the hypophyseal-ovarian unit was determined in control and nephrotic rats by two dynamic tests. In the first one, 10 days after PAN or placebo administration female rats were stimulated with LHRH (300 ng/100 g body wt) and samples were collected at 0, 20, 40, 60 and 80 min after releasing factor administration. The second dynamic test, which was performed in control and nephrotic rats, consists of one (day 10 after PAN) or four (between days 7-10 after PAN) doses of hCG (8 UI), respectively. In all cases, serum samples were collected on day 10. In addition, the relative in vitro biological activity of FSH from control and nephrotic rats before and after LHRH stimulus was determined. The results reveal that after a stimulatory dose of LHRH the secretion of LH was significantly diminished in nephrotic rats at all registered times. By contrast, normal response was observed in terms of FSH secretion in nephrotic females. On the other hand, no ovarian response, in terms of progesterone or estradiol synthesis, was observed in nephrotic rats after either one or four stimuli with hCG Interestingly, in spite of the normal or high concentrations of FSH, the biological activity of FSH was totally abolished in nephrotic rats. On the whole, the results from this study indicate that the nephrotic syndrome had a harmful effect on the pituitary-ovarian unit, and strongly suggest that the endocrine dysfunction could be initiated at the hypophysial level; even though a specific ovarian damage is also predictable.

Evaluation of the pituitary-testicular function during experimental nephrosis

To investigate the pituitary-testicular function in nephrotic rats, a sequence of experiments was undertaken in adult male rats after a single dose of puromycin aminonucleoside (PAN). Endocrine modifications were evaluated chronologically throughout the experimental disease in order to determine the appearance of hormone alterations which lead to the axis dysfunction. Serum concentration of LH, FSH, androstenedione, total and free testosterone, estradiol as well as urine testosterone were measured by specific RIAs on days 3, 7 and 10 after treatment on nephrotic and control groups. Prolactin was also evaluated on day 10. Likewise, total weight of various androgen responsive tissues from both groups was recorded, and the number of androgen receptor (AR) binding sites were determined. To know the functional status of the hipophyseal-testicular unit, groups of nephrotic and control rats were stimulated with LHRH (300 ng/100 g b.w.) or with one or four doses of hCG (8 UI), respectively. Additionally, the relative in vitro biological activity of FSH from nephrotic and control rats before and after LHRH stimulus was determined. The results from the hormonal profile revealed clear endocrine disorders characterized by a progressive diminution of all serum hormones except prolactin and urine testosterone, which remained unmodified. The weight of the main androgen responsive tissues, the ventral prostate and the seminal vesicle, decreased parallelly to androgen diminution. The binding analysis of AR shows a significant elevation of the available androgen sites in all analyzed tissues except kidney and hypothalamus. The secretion of LH and FSH from nephrotic animals after LHRH administration was lower than that from intact animals at the registered times. Interestingly, the biological activity of FSH from nephrotic rats was not detectable at both, before and after LHRH administration. Testicular response to hCG stimuli, in terms of testosterone synthesis was not significantly different in the two groups analyzed with respect to the intact animals. By contrast, no response was observed in terms of estradiol production at either one or four doses of hCG. On the whole, the results presented herein allow us to conclude that experimental nephrosis has a harmful effect on the pituitary-testicular axis, and strongly suggests that the endocrine dysfunction is initiated at the hypophyseal level; even though a specific testicular damage is also present.

Ascites fluid of nephrotic rats: sodium dodecyl sulphate-polyacrylamide gel electrophoresis protein pattern and the renin-angiotensin system

1. The concentration of renin and angiotensinogen (Ao) and the activity of angiotensin I-converting enzyme (ACE) was measured in the ascites fluid of nephrotic rats obtained 8 days after puromycin aminonucleoside (PAN) injection. 2. Ascites fluid, serum and urine proteins of these rats were analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). 3. Renin, Ao and ACE were found in the ascites fluid and the percentage of the ratio ascites fluid/(plasma or serum) ranged from 5.9 to 9.9%. The electrophoretic analysis revealed that the ascites fluid contained low (Mr < 66 kDa) and high (Mr < 66 kDa) molecular weight proteins. Albumin and six proteins higher than 66 kDa were present both in the ascites fluid and in serum from nephrotic rats. 4. Data from the study suggest that some proteins in the ascites fluid, including renin, Ao and ACE, come from the plasma. It is possible that the loss of renin, Ao and ACE to the ascites fluid may be playing a role in the metabolic alterations of these three proteins in PAN-nephrotic rats.

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.

Time course analysis of serum and urinary proteins by SDS-PAGE in experimental nephrotic syndrome

Serum and urinary proteins from rats with nephrotic syndrome (NS) induced by puromycin aminonucleoside (PAN) were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Analysis was made on days 2, 4, 6, 8, 10, 12, 16, 20, and 30 after PAN injection. Data were compared with control rats (C). Rats developed proteinuria on days 4-30 and hypoproteinemia on days 4-16. Total protein concentration in serum and urine was similar on day 6. SDS-PAGE revealed that urinary albumin augmented on days 4-30 and serum albumin decreased markedly on days 4-20. Albumin concentration in serum and urine was similar on days 4-16. In addition, the study examined serum changes of 7 other proteins (designed as A, B, C, D, E, F, and G) which appeared or increased in urine, and whose molecular weights were higher (A, B, and C) or lower (D, E, F, and G) than that of albumin. In serum, protein A remained unchanged; protein B and G increased; proteins C, D, E, and F decreased. The qualitative pattern of urinary proteins remained essentially unchanged on days 4-30. During the intense proteinuria, the serum concentrations of protein B and albumin were similar and the urine concentrations of proteins C and D became comparable to that found in serum. These 7 serum proteins did not show the same behavior although all of them were excreted in urine. These data indicate that in PAN-nephrotic rats: (a) urinary proteins can be of low and high molecular weight, (b) serum proteins can be regulated independently of their urinary excretion and molecular weight, (c) the urine concentration of total protein and some specific proteins can reach values similar to that found in serum during the intense hypoproteinemia, and (d) the qualitative pattern of urinary proteins was unrelated to the magnitude of proteinuria.

Angiotensin I converting enzyme activity in uranyl nitrate induced acute renal failure in rats

Angiotensin I converting enzyme (ACE) was measured in urine, serum, and tissues from rats with acute renal failure (ARF) induced by a single subcutaneous injection (15 mg/kg BW) of uranyl nitrate (UN). Urine was collected daily until day 5, when rats were sacrificed by decapitation for the obtention of blood serum and tissues. Other groups of rats were sacrificed on days 1 and 2. These rats showed proteinuria and polyuria. The damage to the kidney proximal tubule was shown by (a) histological analysis at light and electron microscopy levels on days 1, 2, and 5, (b) the increase in urinary excretion of dipeptidyl aminopeptidase IV and N-acetyl-beta-D-glucosaminidase on days 1-5, and (c) the low molecular weight proteinuria pattern on day 1. In addition, the histological analysis at the ultrastructural level showed normal glomeruli appearance on days 1 and 2, but structural alterations on day 5. These data suggest that the increased urinary excretion of enzymes and proteins is a consequence of the tubular injury on days 1 and 2, and of tubular and glomerular injury on day 5. ACE activity increased in urine on days 1-5 and in serum on day 5. Tissue ACE activity increased in lung, small intestine, and adrenal glands; and remained unchanged in testis, aorta, brain, kidney, heart, and liver. Our data suggest that: (a) the increase in serum ACE may be secondary to the changes in tissue ACE activity, and (b) the urine ACE increase may be due to the kidney proximal tubule damage. This work supports the contention that an increase in urine ACE may be an indicator of injury to the proximal tubule.

Angiotensin I converting enzyme in glycerol-induced acute renal failure in rats

Angiotensin I converting enzyme (ACE) activity was measured in serum, urine, and tissues of rats with acute renal failure (ARF) induced by glycerol. Glycerol-injected rats were subdivided in three groups according to the urinary volume: oliguric, nonoliguric, and polyuric. The damage to the proximal tubule was evident by (a) the histological analysis at light and electron microscopy level, (b) the augmented urinary excretion of the enzymes dipeptidyl aminopeptidase IV and N-acetyl-beta-D-glucosaminidase, and (c) the low molecular weight proteinuria pattern. On the other hand, the appearance of the glomeruli at the ultrastructural level was normal. These data suggest that the increased urinary excretion of enzymes and proteins in these rats is a consequence of the tubular injury. ARF was markedly higher in the oliguric rats. Urine ACE activity increased in the rats of the three groups, but statistical significance was reached only in the oliguric rats. Serum ACE activity increased in the oliguric rats and tissue ACE activity did not change. It is concluded that the high urinary ACE in glycerol-treated rats is associated with the damage to the kidney tubules. These data support the contention that urinary ACE may be another marker of injury to the proximal tubule.

Tissue lipoperoxidation and glutathione peroxidase activity in puromycin aminonucleoside injected rats

1. Lipoperoxidation (LPx) and glutathione peroxidase (GPx) activity were measured in kidney, liver, heart, lung, brain and testis from control and puromycin aminonucleoside (PAN) injected rats on days 1-6, 8, 10, 16 and 22 after vehicle or PAN injection. 2. PAN-injected rats developed proteinuria on day 3. 3. In PAN-injected rats: (a) LPx increased in kidney, liver, lung, brain and testis before day 3 and in heart on day 3; (b) GPx activity increased in kidney, liver, heart, lung and testis and diminished in brain on day 3 or after.