Vitamin D metabolites and growth hormone therapy in uraemic rats: the short-term effect on growth failure and hyperparathyroidism

Summary: The aim of our study was to evaluate the effect of 1,25 dihydroxyvitamin D3 (D), 22-oxacalcitriol (O) or recombinant human growth hormone (GH) on growth failure and hyperparathyroidism in 5/6 nephrectomized uraemic (Ur) rats. Seven groups of rats were studied: (i) sham controls (SC; n =6); (ii) Ur controls (UrC; n =8); (iii) Ur treated either with D (UrD; n =7); (iv) O (UrO, n =8); (v) GH (UrGH; n =7); (vi) D+GH (UrDGH; n =9); or (vii) O+GH (UrOGH; n =7). For 14 days, D and O were administered intraperitoneally daily at 30 ng/kg per day and GH subcutaneously daily at 1.3 i.u./day. Four weeks after 5/6 nephrectomy, plasma creatinine (Cr), plasma and urine calcium (Ca), plasma phosphate (P), ratio of urine Ca/urine Cr, amino-terminal parathyroid hormone (PTH; pg/mL) and Ca/dry bone weight in the left femur (mg/g) were measured. Uraemic controls, UrD, UrO and UrDGH rats were lower in weight gain than SC rats over the study period, but linear growth was not retarded in any uraemic group. Plasma Cr was greatly increased in any Ur group as compared with SC group. Plasma Ca and P concentrations did not differ among each group. the ratio of urine Ca/urine Cr in UrD and UrDGH groups was higher than SC, UrCand UrGH groups. the use of Dor D+GH suppressed PTH, returning the level in these rats to the normal level of the SC rats, while the PTH concentrations in the UrO and UrOGH rats were less decreased. Bone Ca content was enhanced by D+GH and O+GH administration in comparison with UrC rats, but there was no difference in the bone Ca content between UrD and UrDGH rats, and between UrO and UrOGH rats. In conclusion, growth failure in weight was shown in uraemia, but linear growth was not retarded in any uraemic group. 1.25 dihydroxyvitamin D3 and D plus GH successfully suppressed secondary hyperparathyroidism. Further studies are needed in order to elucidate the interactions on bone between vitamin D rnctabolites and GH.     

Growth hormone and renal function

Summary: Recombinant human growth hormone (rhGH) has been recognized to be beneficial for improving growth retardation in uraemic children. the potential effect of growth hormone (GH) on renal haemodynamics results in an increase in glomerular filtration rate and renal plasma flow. However, in GH transgenic mice and uraemic rats treated with GH, GH has been reported to aggravate glomerular sclerosis and induce deterioration in renal function. Therefore, the potential of adverse effect of GH on deterioration in renal function has been of concern in uraemic children receiving rhGH. Growth hormone enhances protein anabolism and promotes a positive nitrogen balance. It is more likely that the anabolic effect of GH used at the conventional dose may reduce renal solute load and slow the progression of end-stage renal failure (ESRF) in rhGH-treated uraemic children. A low protein diet with adequate calories slows the deterioration of renal function in uraemic patients. the effects of GH on growth promotion, renal haemodynamics and protein anabolism are mainly mediated by insulin-like growth factor-I (IGF-I). Insulinlike growth factor-I enhances glomerular filtration rate and promotes glomerular hypertrophy, but IGF-I administration is unlikely to give rise to glomerular sclerosis. the efficacy and the safety of concomitant therapy of recombinant GH or IGF-I and low protein diet should therefore be considered in uraemic children.     

Administration of ghrelin to young uraemic rats increases food intake transiently, stimulates growth hormone secretion and does not improve longitudinal growth.

BACKGROUND: Ghrelin administration stimulates appetite and growth hormone (GH) secretion. Whether these effects are preserved in young individuals with chronic renal failure (CRF) and their potential benefit on growth is questioned. METHODS: Three experiments were performed in subtotally nephrectomized young rats (Nx). (i) Food intake was monitored in CRF rats receiving saline intraperitoneally or a ghrelin dose (30 nmol) shown to increase food intake over 2 and 24 h in rats with normal renal function. (ii) Plasma levels of GH were measured after a dose of intravenous ghrelin (3 nmol) was given to three groups of five rats each: Nx, sham-operated fed ad libitum (SAL) and sham-operated pair-fed with Nx (SPF). (iii) Growth of Nx rats treated with intraperitoneal ghrelin (3 nmol) for 7 days (Nx-Ghr) was compared with that of SAL and Nx groups receiving saline (n=8-10 per group). RESULTS: In CRF rats, the dose of 30 nmol of ghrelin increased food consumption for 2 h (1.3+/-0.2 g vs 0.5+/-0.2 g, P<0.05) but not 24-h food intake (12.5+/-0.6 g vs 12.2+/-0.5 g). Ghrelin (3 nmol) increased plasma levels of GH, which were maximal 10 min after injection, no differences being observed among groups (SAL: 666.2+/-104.6 ng/ml; Nx: 691.6+/-90.7 ng/ml; SPF: 577.8+/-125.4 ng/ml). Return to basal GH levels was delayed in Nx. Ghrelin did not improve body length and weight gains, longitudinal bone growth rate or food intake in the Nx-Ghr group. CONCLUSIONS: In young uraemic rats, ghrelin increases appetite but not 24-h food intake, stimulates GH secretion and does not improve growth.     

Compensatory renal growth after unilateral nephrectomy in the ovine fetus.

Unilateral nephrectomy of the adult animal results in compensatory renal growth but does not involve formation of new nephrons. It is not clear whether compensatory growth can occur during the period of active nephrogenesis in utero and if so, whether more nephrons can be formed. Male ovine fetuses (n = 20) underwent unilateral nephrectomy (n = 10) or sham nephrectomy (n = 10) at 100 d of gestation (term, 150 d). After 27 to 34 d, ewes and fetuses were killed and the right kidney of each fetus was removed and weighed. The wet weight of the right kidney was greater in the unilaterally nephrectomized fetuses (16.3 +/- 1.3 g compared with 12.2 +/- 0.7 g; mean +/- SEM, P < 0.05) as was the kidney to body weight ratio (5.2 +/- 0.3 g/kg compared with 3.8 +/- 0.2 g/kg; P < 0.001). Nephron number in the right kidney was estimated by an unbiased stereologic technique. There was a 45% increase in the number of nephrons in the kidneys from unilaterally nephrectomized animals compared with the kidneys from sham-operated animals (530,763 +/- 37,136 nephrons in the unilaterally nephrectomized group compared with 365,672 +/- 36,016 nephrons in the sham-operated group; P < 0.01). Mean glomerular volume was lower in the unilaterally nephrectomized group; however, total glomerular volume per kidney was not different between groups. This study demonstrates that there is a significant amount of compensatory growth and nephron endowment in a remaining kidney after unilateral nephrectomy during the period of active nephrogenesis in the sheep. This is the first time such events have been shown to occur in utero.     

Growth hormone secretion from pituitary cells in chronic renal insufficiency.

To examine whether growth hormone (GH) secretion is adversely affected by chronic renal insufficiency (CRI), the GH secretory response of dispersed anterior pituitary cells perifused with GH-releasing hormone (GHRH) was investigated in 5/6 nephrectomized (CRI, N = 18) and sham-operated (N = 18) rats. Two weeks after nephrectomy, during a period of stable uremia, CRI rats had significantly higher serum concentrations (mean +/- SEM) of urea nitrogen and creatinine than sham rats, 16.8 +/- 1.4 mmol/liter (47 +/- 4 mg/dl) and 79.6 +/- 0.0 mumol/liter (0.9 +/- 0.0 mg/dl) versus 6.1 +/- 0.4 mmol/liter (17 +/- 1 mg/dl) and 35.4 +/- 0.0 mumol/liter (0.4 +/- 0.0 mg/dl), respectively (P less than 0.0001). Incremental gains in body weight and nose to tail-tip length of CRI rats over two weeks were also significantly depressed, 53.3 +/- 5.38 g (CRI) versus 87.0 +/- 3.78 g (sham; P less than 0.0001) and 3.2 +/- 0.2 cm (CRI) versus 3.6 +/- 0.1 cm (sham; P less than 0.05). The cumulative food intake as well as food efficiency (g food consumed/g weight gain) were also adversely influenced by the uremic state: food intake 304 +/- 1 g (CRI) versus 397 +/- 6 g (sham; P less than 0.0001) and food efficiency 0.173 +/- 0.013 g/g of weight gain (CRI) versus 0.219 +/- 0.008 g/g of weight gain (sham). No significant difference in GH secretory rate (ng/min/10(7) cells) was found between the uremic and sham animals under basal conditions, 65.2 +/- 2.1 (CRI) and 67.9 +/- 2.2 (sham) or in response to GH-releasing hormone, 282.8 +/- 42.4 (CRI) versus 306.2 +/- 42.6 (sham).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of 1,25-dihydroxyvitamin D3 on intestinal glucose absorption in uremic rats

The effect of 1,25-dihydroxyvitamin D3 (1,25-D) on the absorption of glucose in the small intestine was studied in five-sixths nephrectomized uremic rats and sham-operated rats. Four weeks after the nephrectomy, the uremic animals were divided into two groups: One group was given 1,25-D (300 pmol/kg body weight/day, three times per week) intraperitoneally, and the other was left untreated. One week after the 1,25-D treatment, an in vivo glucose absorption test was performed at 00.00 h in consideration of the circadian rhythm of glucose absorption. In untreated uremic rats, the glucose absorption rate was lower than in sham-operated rats. In 1,25-D treated uremic rats, the glucose absorption rate was higher than in untreated uremic rats and not lower than in sham-operated rats. These results suggest that the absorption rate of glucose of the small intestine is reduced in uremic rats and that it is recovered on treatment with 1,25-D.     

IGF-I inhibitors reduce compensatory hyperfiltration in the isolated rat kidney following unilateral nephrectomy.

BACKGROUND: A role for insulin-like growth factor-I (IGF-I) as a mediator of renal hyperfiltration and hyperperfusion following unilateral nephrectomy (UNx) has been examined. METHODS: Adult male Wistar rats were subjected to either left UNx or sham operation. Twenty one days after surgery, the right kidney was removed under barbiturate anaesthesia, and renal function was measured ex vivo using an isolated rat kidney perfusion system. The glomerular filtration rate was assessed from the renal clearance of [(14)C]inulin. RESULTS: UNx stimulated renal growth as shown by a significantly higher (P<0.02) tissue dry weight in kidneys from UNx (0.45+/-0.02 g) than from sham-operated rats (0.31+/-0.02 g). Compensatory hyperfiltration could be detected ex vivo; kidneys obtained from UNx rats having a significantly higher (P<0.05) [(14)C]inulin clearance (0.75+/-0.08 ml/min, n=8) than kidneys obtained from sham-operated animals (0.39+/-0.05 ml/min, n=8). Compensatory hyperperfusion was also detected ex vivo; kidneys obtained from UNx rats having a significantly higher (P<0.05) renal perfusate flow (28.2+/-2.7 ml/min) than kidneys obtained from sham-operated rats (22.5+/-0.8 ml/min). Following perfusion with either 50 microg monoclonal IGF-I antibody (n=4) or 6.5 microM genistein (n=4), an inhibitor of tyrosine kinase, no significant difference in [(14)C]inulin was observed between kidneys obtained from either UNx or sham-operated rats. In contrast to hyperfiltration, renal hyperperfusion remained unaffected by the IGF-I antibody and was only reduced by 30% following genistein administration. CONCLUSIONS: The results suggest a role for renal IGF-I as a mediator of compensatory hyperfiltration in the rat.     

Effects of grwoth hormone therapy and malnutrition on the growth of rats with renal failure

We examined the effects of methionylhuman growth hormone (met-hGH) and malnutrition on the growth of 5/6 nephrectomized rats and sham-operated controls. One group of shamoperated rats (PFS) was pair-fed with a group of nephrectomized rats in renal failure (RF); another group of sham-operated rats was fed ad libitum (ALS), and a final group of rats with renal failure (RF-GH) was treated with 4 IU/day met-hGH. After 4 weeks, RF-GH rats gained 12.3±1.7 cm in length; this was more than the 10.2±1.2 cm gain of RF rats (P<0.05). Ingested food was converted into weight gain more efficiently by RF-GH rats than RF rats (267±26 vs 235±38 mg weight gain/g food intake,P<0.05). RF-GH rats also gained more weight (122±25 g) than RF rats (98±27 g), but this difference was not significant (0.05<P<0.1). Insulin-like growth factor (IGF)-I, glucose and insulin levels were not different between RF and RF-GH rats. Food intake of RF and PFS rats was 64% of ALS intake and was associated with poor gains in weight and length by the PFS and RF groups (relative weight and length gains were ALS>PFS>RF,P<0.05 for all comparisons); this suggests that the poor growth of RF rats when compared with PFS rats was due to factors other, than food intake. Serum IGF-I levels of 771±249 ng/ml in PFS rats were lower than levels of 1109±253 ng/ml found in the ALS group (P<0.05); this is consistent with the malnourished state of PFS rats. Serum IGF-I levels in RF rats (950±236 ng/ml) were not different from ALS or PFS levels despite the fact that RF rats gained less weight and length than either the ALS or PFS rats. We conclude that RF rats increase in length, use ingested calories more efficiently, and fail to develop marked insulin resistance when treated with met-hGH. We find that, in addition to poor food intake, other factors contribute to growth failure in this model of renal failure. Finally, we find that RF rats have normal levels of IGF-I, suggesting that low IGF-I levels are not a major cause of growth failure in rats with renal failure.     

Effect of exercise training on glomerular filtration rate of mice with various degrees of renal mass reduction.

We studied the effect of repeated heavy physical activity on glomerular filtration rate (GFR) in healthy, uninephrectomized and experimentally uremic mice. Exercise consisted of running uphill in the inner surface of a rotating cylinder in ideal environmental temperature. In the control groups, no extra physical activity was imposed. In sham-operated and nephrectomized mice, GFR rose significantly following training. By contrast, GFR did not change significantly in the exercised mice with experimental renal failure 24 h following the last exercise session. During the same period, no significant change was observed in GFR of any of the control groups. Following training in each experimental group, mean aortic blood pressure as well as fractional kidney weight (kidney weight/body weight) were not different from the respective controls. Our results indicate that the capacity to augment GFR by physical training is dependent upon the amount of remaining functional renal tissue.     

Development of focal glomerulosclerosis after unilateral nephrectomy in infant rats

Rats unilaterally nephrectomized in infancy (Nx5) or in adulthood (Nx55) and fed a normal (21%) protein diet were studied at 2, 3 and 6 months after surgery with regard to glomerular filtration rate (GFR) and the development of both albuminuria and focal glomerulosclerosis (FGS) in the remnant kidney. Nx rats were compared with sham-operated animals (S) of corresponding age. The incidence of FGS never exceeded 1.4% in S rats. In Nx5 rats the incidence of FGS was not increased at 2 and 3 months after surgery whereas it was significantly higher (range 10%–27%) than in S rats 6 months after surgery. Urinary albumin excretion was significantly increased in Nx5 rats 2 months after surgery and was even higher 6 months after surgery. In Nx55 rats the incidence of FGS was the same as in Nx5 rats 2, 3 and 6 months after surgery, but urinary albumin excretion was significantly lower than in Nx5 rats 6 months after surgery. The GFR expressed per unit of body weight decreased in both Nx5 and S5 rats from 2 to 6 months, but the decrease was more pronounced in Nx5 rats than in S5 rats. The GFR factored by kidney weight was significantly lower in Nx5 than in any of the other groups at the 6-month follow-up study. We conclude that, as in adults, when unilateral nephrectomy is performed in infancy, FGS will develop in the remnant kidney. More pronounced albuminuria and reduction of GFR may indicate that the glomerular lesion is more severe in rats nephrectomized in infancy than in adulthood.     

Effects of immobilization stress on kidneys of Wistar male rats: a morphometrical and stereological analysis

This paper verifies the morphological changes induced by immobilization stress on the kidney of rats by using stereological methods. Fifteen 4-week-old Wistar male rats were randomly assigned to control (n = 7) and stressed (n = 8) groups. Stress stimuli were performed over 5 weeks by immobilization of the rats for 2 h daily in a rigid opaque plastic cylinder that restrained their movements. Increases in the adrenal mass index (p < 0.05) and decreases in serum testosterone levels (p < 0.05) demonstrated the efficacy of the stressor stimuli. Stressed rats presented diminished body weight gain when compared to controls (p < 0.05). The mean values of kidney weight, kidney volume, kidney volume index and glomerular volume density were significantly lower in the stressed group (p < 0.05); nevertheless, no significant difference was found in the cortical/medullar ratio or in the volume-weighted mean glomerular volume. The number of glomeruli per kidney was 45% lower in the stressed group (p < 0.0001), but no change in serum creatinine levels was found. However, the morphological alterations may have serious implications predisposing individuals to renal disease and hypertension in adult life.     

Mesangial function and glomerular sclerosis in rats after unilateral nephrectomy

To investigate the possible relationship between disturbance of mesangial function and segmental localization of glomerular sclerosis, five uninephrectomized male Wistar rats and five sham-operated controls received colloidal carbon intravenously. At 4 months 8.4 +/- 2.5% of the glomeruli of the nephrectomized rats showed focal sclerosis. Glomeruli of nephrectomized rats contained significantly more carbon than glomeruli of controls. Glomeruli with focal sclerosis contained significantly more carbon than normal glomeruli in the same kidneys with a preferential tracer localization within the lesions. In another experiment carbon injections were given before surgery. At 4 months 12.6 +/- 4.1% of the glomeruli of the nephrectomized rats showed focal sclerosis, an incidence not significantly different from that of the first experiment. Glomerular carbon content was equal in experimental and control rats and no preferential localization of the tracer within the lesions was found. From these results we conclude that the preferential localization of carbon in the glomerular lesions in rats nephrectomized before injection of carbon is caused by the increased delivery of tracer shortly after injection to those glomerular areas where sclerosis will develop at a later time. The development of focal sclerosis may be related to the local deposition of harmful substances from the circulation.     

The role of growth hormone and insulin-like growth factor-I in experimental renal growth and scarring

Recent evidence suggests a causal link between early renal/glomerular hypertrophy and late kidney scarring and glomerular sclerosis. Insulin-like growth factor-I (IGF-I) is a growth-promoting peptide likely to play a role in the development of kidney growth. We observed an increased renal IGF-I content in two experimental models of accelerated kidney growth in the rat. By contrast, diabetic renal hypertrophy is abolished in the absence of growth hormone (GH). Dietary protein manipulations affect the expression of compensatory renal growth (CRG), as well as renal IGF-I content. The renotrophic effect of a high-protein diet on CRG seems GH-dependent and IGF-I-mediated. GH also appears to have a permissive role on the development of progressive renal scarring following extensive renal ablation in rats, as dwarf rats seem somewhat resistant to the development of accelerated scarring and renal failure.     

Growth failure and decreased levels of insulin-like growth factor I in obstructive jaundice are reversed by bile diversion

Insulin-like growth factor I (IGF-I) is one of the principal stimuli of linear growth. Growth failure in children with chronic cholestatic jaundice may be related to decreased hepatic synthesis of IGF-I. It was hypothesized that (1) biliary obstruction would lead to growth retardation and decreased circulating IGF-I levels; and (2) surgical drainage of the obstructed biliary system would reverse these effects. To test this hypothesis, the following study of male Sprague-Dawley rats (135 g; 10 animals per group) was performed. Group I underwent common bile duct ligation (CDL); group II underwent choledochoduodenostomy 2 weeks following CDL; group III were sham-operated and fed with CDL rats; and group IV were sham-operated and fed ad libitum. Daily food intake and weekly body weight were recorded. Statistical analysis was by repeated-measures analysis of variance and individual comparisons were evaluated by Student's t test. Biliary obstruction results in decreased food intake, rate of weight gain, and IGF-I levels. A significant reduction in IGF-I levels was also noted in the pair-fed sham-operated rats (group III). Relief of obstructive jaundice by surgical drainage results in a reversal of these changes. It is concluded that the growth failure and decreased IGF-I levels associated with obstructive jaundice can be reversed by surgical drainage of the obstructed biliary system and, in part, are due to inadequate nutrition.     

Correction by oral adsorbent of abnormal digestive tract milieu in rats with chronic renal failure

In order to examine the mechanism by which the oral carbonaceousadsorbent, AST-120 delays the appearance of glomerular sclerosis,experiments were carried out in 120 male Sprague-Dawley ratsweighing 285–320 g. The rats were first subjected to 2/3,3/4, and 4/5 nephrectomy (n=40). The experiments were begunat 2 weeks after the surgery, and were performed over an 8-weekperiod. Half of each group (n=20) was administered 1 g/day ofliquid AST-120, and the other half received liquid vehicle solutionwith pair feeding in each group. In the 2/3 nephrectomized groupthe administration of AST-120 delayed the occurrence of glomerularhypertrophy and prevented the appearance of glomerular sclerosiswithout any significant differences in renal function, systemicblood pressure (SBP), and urinary protein excretion (U-P). Inthe 3/4 nephrectomized group the administration of AST-120 delayedthe appearance of glomerular hypertrophy and sclerosis withsignificant decreases in SBP and U-P. In the 4/5 nephrectomizedgroup the administration of AST-120 delayed the appearance ofglomerular sclerosis and prevented a decrease in renal function.It is concluded that administration of the oral adsorbent AST-120delays the occurrence of glomerular sclerosis by delaying theappearance of glomerular hypertrophy, systemic hypertension,and the increase in proteinuria. It can be therefore mentionedthat the accumulating substances in the digestive tract worsenthe abnormal milieu of chronic renal failure.     

Improvement of growth and food utilization by human recombinant growth hormone in uremia

We compared growth rate, food conversion ratio and morphology of the growth zone in female Sprague-Dawley rats with subtotal nephrectomy or sham operation. Both groups were either given vehicle or 1.4 IU/day recombinant human growth hormone (GH) by s.c. osmotic minipump, or 2.5 IU twice daily intraperitoneally for 14 or 20 days, respectively. Compared to uremic rats infused with vehicle, infusion of GH significantly (P less than 0.01) improved growth; that is, it increased gain of weight (delta 27.0 +/- 7.7 g vs. 11.6 +/- 4.9 g) and length (delta 1.8 +/- 0.3 cm vs. 1.12 +/- 0.44 cm) in ad libitum fed uremic rats. This was accompanied by increased food utilization ratio (0.146 vs. 0.065 g weight gain per g food intake). A similar increment of growth and food utilization ratio was also observed in GH versus solvent infused controls, either pairfed as for the uremic animals or fed ad libitum. Despite administration of GH, growth was not completely restored to normal in uremic animals. Circulating immunoreactive IGF I was not significantly increased by GH infusion in either uremic animals or controls. Histological analyses of the proximal tibia showed increased rate of longitudinal growth, as evaluated by tetracyclin-labeling, and increased volumetric density of primary spongiosa with unchanged width of primary spongiosa trabecules when GH was infused in uremic animals. The data suggest that growth impairment in the uremic rat is partially responsive to GH, and this is not accompanied by an increase of circulating IGF I. Therapeutic trials with recombinant GH in uremic children appear justified.     

Enzyme induction in the uremic liver.

Forty-five days after subtotal nephrectomy or sham-operation of male rats, microsomal enzymes were investigated in vitro. The activities (per milligram) of microsomal protein of two esterases and of two glucuronyltransferases were normal in the uremic rats. The mixed-function oxidation system had lower activities per milligram of protein than that in sham-operated controls. Due to a decrease of the microsomal protein content of the uremic liver, the activities of these enzymes were decreased when calculated for the whole liver. In contrast, the glucoronidation of phenolphthalein remained normal when related to the whole liver, due to an increased activity per mg of protein. Treatment with the plasticizer di-(2-ethylhexyl)-phthalate caused a significant increase of the liver wet weight, the microsomal protein content, and the activity per mg of protein for the demethylation of aminopyrine in subtotally nephrectomized rats but was without influence on the liver of sham-operated controls. It is concluded that uremia itself does not induce liver microsomal enzymes. The microsomal enzymes, however, remain inducible by foreign compounds even under uremic conditions.     

Progressive glomerular sclerosis and renal failure in rat with 7/8 nephrectomy model

A model of progressive glomerular sclerosis and chronic renal failure was established in 7/8 nephrectomized rats. Three fourths of left kidney of six-week old Sprague Dawley rats were ligated and removed. One week later right kidney was removed. As controls 3/4 nephrectomized rats operated the same manner as 7/8 nephrectomized rats and sham operated rats were used. Remarkable excretion of the protein into the urine and rise in blood pressure were noted in all 7/8 nephrectomized rats. Eight weeks after 7/8 nephrectomy, serum creatinine rose as high as 2.8 +/- 0.3 mg/dl and BUN 260 +/- 65 mg/dl. In contrast, only minor degree of elevation of blood pressure, excretion of protein into the urine and elevation of serum creatinine were noted in 3/4 nephrectomized rats. Morphologically deposition of rat IgG, C3, fibrinogen and albumin were observed mainly on the capillary wall in 7/8 nephrectomized rats. Minor amount of deposition was observed in 3/4 nephrectomized rats. By light microscopy there were remarkable glomerular and tubular lesions in 7/8 nephrectomized rats. Most of the glomeruli showed hypertrophy, 40% of the glomeruli had cellular or fibrocellular crescent, 34% of glomeruli failed into global sclerosis or hyalinosis, tubular atrophy or enlargement and hyaline cast in the lumen and interstitial fibrosis were also noted. By electron microscopy detachment of epithelial and endothelial cells from the GBM, increase in the mesangial matrix, obliteration of the capillary lumen by fibrin, hyaline material were observed. Only minor degree of increase in mesangial matrix and epithelial degenerative lesions were observed and 3% of glomeruli were sclerosed in 3/4 nephrectomized rats. From these results 7/8 nephrectomized rats can serve as useful model for studying the mechanism of glomerular sclerosis or hyalinosis and effect of various drugs on glomerulonephritis.     

Acute blood pressure effects and chronic hypotensive action of calcimimetics in uremic rats

A previous study in subtotally nephrectomized (SNX) rats suggested beneficial effects of the calcimimetic R-568 beyond the control of mineral metabolism. This study analyzed potential blood pressure (BP)-lowering effects of R-568. Male Sprague-Dawley rats received two-stage subtotal nephrectomy or sham operation. Telemetry devices were inserted into the abdominal aorta, and BP was measured every 5 min. R-568 (20 mg/kg per d) or solvent was infused for 4 wk followed by once-daily subcutaneous injections for 2 wk. Total body sodium was measured by neutron activation analysis. The uremia-induced increase of mean arterial pressure from baseline to day 42 in SNX solvent rats (103+/-5 to 128+/-14 mmHg, P=0.006) was attenuated by R-568 (104+/-5 to 111+/-8 mmHg; P<0.0001 for difference of slopes). The circadian rhythm was abrogated in SNX rats and not restored by R-568. In sham-operated rats, R-568 had only a minor transient antihypertensive effect. R-568 injection induced a transient rise of mean arterial pressure by 23+/-4 and 26+/-10 mmHg in sham and SNX rats but only by 9+/-3 and 10+/-5 mmHg in solvent-treated rats (P<0.01 versus baseline and solvent versus R-568). Plasma angiotensin-converting enzyme activity and aldosterone levels were similar; food intake and physical activity did not differ throughout the study. In healthy rats, total body sodium was higher after 14 d of R-568 compared with solvent infusion (37.1+/-4 versus 32.5+/-1.4 mmol/kg; P=0.01). The calcimimetic R-568 causes an initial BP increase in sham-operated and uremic rats, which in uremic rats is followed by a marked and sustained antihypertensive effect.     

Mycophenolate mofetil prevents the progressive renal failure induced by 5/6 renal ablation in rats

BACKGROUND: Extensive renal ablation is associated with progressive sclerosis of the remnant kidney. Because lymphocytes and monocytes accumulate in the remnant kidney, it is likely that they play a role in the renal scarring. Therefore, we treated rats with 5/6 nephrectomy (5/6Nx) with mycophenolate mofetil (MMF), a drug that has an antiproliferative effect and that suppresses the expression of intercellular adhesion molecules. METHODS: Sprague-Dawley rats with 5/6Nx received MMF (30 mg. kg-1. day-1 by daily gastric gavage, N = 15) or vehicle (N = 16). Ten additional rats were sham operated. All rats were fed a 30% protein diet. Body weight, serum creatinine, and urinary protein excretion were determined weekly. Lipid peroxidation, as a measure of oxidative stress observed by urinary malondialdehyde determinations, was performed every two weeks. Histologic studies were done in the remnant kidney four weeks (9 rats from the vehicle-treated group, 7 rats from the MMF group, and 5 sham-operated rats) and eight weeks after surgery (the remaining rats). Glomerular volume, sclerosis in glomeruli (segmental and global) and interstitium (semiquantitative scale), infiltrating lymphocytes and macrophages (CD43- and ED1-positive cells), and expression of adhesion molecules (CD54, CD18, and CD11b) were analyzed. RESULTS: MMF treatment prevented the progressive increment in serum creatinine and the proteinuria observed in the 5/6 nephrectomized rats during the eight weeks of observation (P < 0.01). Weight gain was comparable in the MMF-treated and sham-operated rats, whereas weight gain was decreased in untreated 5/6 nephrectomized rats. Excretion of malondialdehyde increased after surgery but returned sooner to control levels in the MMF-treated rats. Increments in glomerular size and mean arterial blood pressure induced by renal ablation were not modified by MMF treatment. Eight weeks after surgery, segmental sclerosis was present in 48.4 +/- 8.35% (+/- sd) glomeruli in the vehicle-treated group versus 25 +/- 10.5% in the MMF-treated group (P < 0.001). Interstitial fibrosis was reduced significantly with MMF treatment (P < 0.001). Infiltration with CD43- and ED1-positive cells in glomeruli and interstitium was two to five times lower in MMF-treated rats (P < 0.01). Expression of adhesion molecules CD18 and CD11b was similarly reduced. CONCLUSION: MMF ameliorates the progressive renal damage in the remnant kidney after 5/6Nx. This effect is associated with a reduction in the infiltration of lymphocytes and monocytes, whereas glomerular hypertrophy and systemic hypertension are unchanged.