Effects of dietary protein conditioning on gentamicin-induced nephrotoxicosis in healthy male dogs.

Eighteen 6-month-old male Beagles with normal renal function were allotted at random to 3 groups of 6 dogs each. For 21 days, each group was fed a diet that was similar except for protein content (high protein, 27.3%; medium protein, 13.7%; and low protein, 9.4%). After the conditioning period, gentamicin was administered at a dosage of 10 mg/kg of body weight, IM, every 8 hours for 8 days, and the respective diet was continued. Clearance of endogenous creatinine, 24-hour urinary excretion of protein and enzymes (gamma-glutamyltransferase, and N-acetyl-beta-D-glucosaminidase, and fractional clearance of sodium and potassium (%) were determined before and after dietary protein conditioning and on days 2, 4, 6, and 8 of gentamicin administration. Additionally, trough serum gentamicin concentration was determined on days 2, 4, 6, and 8 of gentamicin administration. At the end of the study, all dogs were euthanatized; renal histologic features were graded, using a continuous ranking scale, and renal cortical gentamicin concentrations were measured. Data were ranked and analyzed, using a nonparametric equivalent of a two-way ANOVA; P < 0.05 was considered significant. After the dietary conditioning period (prior to gentamicin), dogs fed the high-protein diet had higher endogenous creatinine clearance and urinary excretion of protein, compared with dogs fed the low-protein diet. Differences existed among groups after 8 days of gentamicin administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of a low protein diet on radiation nephropathy in the pig.

Nine mature, approximately 45-week-old pigs, were fed a standard diet (SD) containing 16% protein; 10 pigs were fed an isocaloric low protein (LP) pig feed containing 4% protein 2 weeks prior to and 16 weeks after renal or sham-irradiation. The pigs then received the SD for a further 4 weeks. Both kidneys of seven pigs fed the LP diet, and six pigs fed the SD, were irradiated with a single dose of 9.8 Gy of 60Co gamma-rays. The remaining pigs received sham-irradiation. The individual kidney glomerular filtration rate (GFR), effective renal plasma flow (ERPF), and the haematocrit were serially measured before and up to 20 weeks after irradiation. The radiation-induced reduction in mean individual kidney GFR, expressed as either absolute values or as a percentage of the respective sham-irradiated controls, was significantly greater in pigs fed the SD compared with pigs fed the LP diet (p < 0.05). In contrast, the radiation-induced reduction in mean individual kidney ERPF, expressed as absolute values, observed in pigs fed the SD was not significantly different from that seen in pigs fed the LP diet. However, if these data were expressed as a percentage of the respective sham-irradiated controls, then a significantly greater reduction in ERPF was seen in pigs fed the SD compared with pigs fed the LP diet (p < 0.001). Morphological analysis of renal tissue removed 20 weeks after irradiation showed that the extent and severity of the glomerular lesions seen in pigs fed the SD were significantly reduced in pigs fed the LP diet. Thus dietary protein restriction appears to reduce some of the signs of radiation nephropathy in the pig.

Sequential evaluation of radiation-induced glomerular ultrastructural changes in the pig kidney.

Both kidneys of 12 mature female pigs received either a single dose of 9.8 Gy 60Co gamma rays or sham irradiation. At intervals of 1-4 weeks serial renal biopsies were obtained, followed by sacrifice at 24 weeks after irradiation. Individual kidney glomerular filtration rate (GFR), effective renal plasma flow (ERPF), and the hematocrit (Hct) were measured routinely. Renal irradiation resulted in a progressive decline in GFR, ERPF, and Hct, with minimal values being observed within 12 weeks of irradiation. No change in any of these parameters was noted in the sham-irradiated pigs. The initial morphological change in irradiated glomeruli was leukocyte attachment to capillary endothelial cells 3-6 weeks after irradiation followed by activation and swelling of the endothelial cells. This was followed by pronounced increases in capillary permeability with fluid and erythrocyte, leukocyte, and platelet exudation into the subendothelial/mesangial space. This resulted in compression of glomerular capillary lumina, which occurred concomitantly with the reduction in GFR. By 12 to 15 weeks after irradiation the changes in endothelial cells were less evident. However, mesangial cells exhibited evidence of activation and proliferation accompanied by progressive mesangial expansion and sclerosis. Thus the glomerular capillary endothelial and mesangial cells appear particularly important in the pathogenesis of radiation nephropathy.

Capillary endothelium. Target site of renal radiation injury.

BACKGROUND: Therapeutic abdominal irradiation may be accompanied by late occurring progressive renal disease associated with glomerular mesangial sclerosis and tubular degeneration. Pathogenesis of this lesion is disputed. EXPERIMENTAL DESIGN: Kidneys of mature pigs were irradiated with a single dose of 9.8 Gy 60Co gamma-rays; serial individual kidney glomerular filtration rate and renal biopsies were obtained at 3-4-week intervals with death 24 weeks after irradiation. RESULTS: Irradiated pigs displayed a progressive reduction in glomerular filtration rate with minimal values observed 12 weeks postirradiation. Morphologic changes in irradiated glomeruli were characterized by leukocytic attachment to capillary endothelial cells 3-6 weeks after irradiation followed by activation and swelling of endothelial cells and occasional microthrombi formation. Similar changes were noted focally in peritubular capillaries with accompanying tubular degeneration and atrophy. In glomeruli these endothelial cell changes were followed by increased capillary permeability and fluid, erythrocyte, platelet, and leukocytic exudation into the subendothelial/mesangial space resulting in compression of glomerular capillary lumina. By 12 weeks postirradiation mesangial cells showed evidence of activation and proliferation accompanied by progressive mesangial expansion and sclerosis with continued reduction of glomerular filtration rate. CONCLUSIONS: It is concluded that endothelial cell injury represents the primary site of radiation damage in the kidney and that the progressive glomerular mesangial sclerosis and reduced renal function of radiation nephropathy may be associated with exposure of capillary elements to various vasoactive and growth promoting factors that stimulate mesangial contraction and proliferation resulting in reduced glomerular filtration area and glomerular filtration rate.

Long-term studies of cisplatin-induced reductions in porcine renal functional reserve.

Mature Large White female pigs aged approx. 10 months received single intravenous doses of 1.5, 2, or 2.5 mg/kg cisplatin. The glomerular filtration rate (GFR) and the effective renal plasma flow (ERPF) in individual kidneys were measured prior to and at 4-week intervals for up to 24 weeks after cisplatin administration by renography using [99mTc]-diethylenetriamminepentaacetic acid (DTPA) and iodohippurate sodium I 131, respectively. The left kidney of each cisplatin-treated pig and that of three age-matched control pigs was then removed, and GFR and ERPF values were measured in the remaining kidney at 4-week intervals for a further 24 weeks after unilateral nephrectomy (UN). Pigs treated with cisplatin showed no significant reduction in GFR or ERPF for up to 24 weeks after drug infusion. As measured using inductively coupled plasma mass spectrometry, the mean renal platinum concentration in the left kidney removed at UN was 77.5 +/- 9.1 ng/g kidney per mg/kg cisplatin. Histological evaluation of these kidneys revealed narrow interconnecting rays of interstitial fibrosis in the deep cortex and medulla; in these areas, glomeruli exhibited thickened Bowman's capsules and occasionally shrunken sclerotic capillaries. In cisplatin-treated pigs, UN was associated with a marked reduction in the ability of the remaining kidney to increase its function in terms of GFR and, to a lesser extent, of ERPF. The increase seen in GFR following UN in the cisplatin-treated pigs was only ca. 50%-70% of that seen in age-matched UN controls. Histologically, these kidneys revealed resolution of the peritubular fibrosis observed at UN; occasional sclerotic glomeruli were also evident. Platinum remained detectable in these kidneys, the mean levels being 18.8 +/- 4.9 ng/g kidney per mg/kg cisplatin. These findings confirm previous observations and illustrate the need for caution in considering further treatment of patients who have previously received cisplatin along with a second potentially nephrotoxic agent.

The protective activity of ICRF-187 against doxorubicin-induced cardiotoxicity in the rat.

The protective activity of the bisdioxopiperazine ICRF-187 against the cardiotoxicity of doxorubicin was evaluated in the rat using both functional and histological assays. Animals that had received a single i.v. dose of doxorubicin (4 mg/kg) alone were compared with those that had been pretreated with a single i.v. injection of saline or ICRF-187 (40 or 60 mg/kg). All rats showed a transient reduction in body weight during the first 3 weeks after drug administration. The greatest reduction (approximately 16%) was observed in animals that had received a combination of ICRF-187 (40 or 60 mg/kg) and doxorubicin. Deaths related to cardiotoxicity were observed only in rats that had received doxorubicin alone and in those treated with saline; most of the deaths occurred at between 8 and 13 weeks after drug administration. Sequential assessments of heart function showed a persistent depression of cardiac output in animals that had received doxorubicin, with or without pretreatment with ICRF-187. The reduction in cardiac output observed in rats that had been pretreated with ICRF-187 (40 or 60 mg/kg) amounted to approximately 15% and approximately 30% after 12 and 20 weeks, respectively, indicating that cardioprotection was only partial. Nevertheless, this represented a marked improvement as compared with the approximately 35% reduction in cardiac output measured at 12 weeks in animals that had received doxorubicin but without pretreatment with ICRF-187. Histological examination of animals that had died during the course of the study and had received doxorubicin after pretreatment with saline revealed severe myocardial lesions typical of doxorubicin-induced damage. In contrast, animals that had been pretreated with ICRF-187 and survived for up to 20 weeks after treatment showed a marked amelioration of these lesions. The present findings may be interpreted as a true cardioprotection or a delay in the onset of the cardiotoxicity of doxorubicin resulting from pretreatment with the bisdioxopiperazine ICRF-187. Although prior and ongoing clinical trials clearly indicate that ICRF-187 protects patients well against doxorubicin-induced heart damage, further investigations are required before high doses of ICRF-187 can be used as a means of increasing the protective activity of this drug against doxorubicin-induced cardiotoxicity.

A morphological study of radiation nephropathy in the pig.

Both kidneys of mature pigs received a single dose of 9.8 Gy 60Co gamma rays. Pigs were killed between 2 and 24 weeks after irradiation and the kidneys examined histologically. Glomerular and tubular changes were observed within 2 weeks of irradiation. Neutrophils and other leukocytes were seen within glomerular capillary loops; mesangial matrix and cell number increased. A progressive increase in thickening of the basement membrane and a decrease in capillary lumina were then noted. Basement membrane duplication occurred within 12 weeks. By 24 weeks these lesions had increased in severity, sclerotic endstage glomeruli, predominantly subcapsular or juxtamedullary, being evident. Tubular lesions initially consisted of focal areas of tubular atrophy in the juxtamedullary region. By 6 weeks subcapsular foci of tubular degeneration, regeneration, and necrosis were found; these appeared to resolve 12 weeks after irradiation. At later times the severity of the tubular lesions varied between pigs, with some exhibiting interstitial fibrosis involving a complete band of subcapsular tissue, while others showed relatively mild changes. There was no apparent change in the vasculature. These findings indicate that (a) there is no one target or dose-limiting cell, and (b) the vasculature does not play a primary role in the development of radiation nephropathy.

Mesangial macromolecular uptake in captopril-treated uninephrectomized rats.

Captopril, an angiotensin II-converting enzyme inhibitor, ameliorates the renal mesangial lesions associated with subtotal nephrectomy, a process associated with increased mesangial macromolecular flux and injury. In the present study uninephrectomized rats with proteinuria and focal glomerular sclerosis had increased mesangial heat-aggregated human IgG (AHIgG) uptake. However, uninephrectomized rats treated daily with captopril, which failed to develop either glomerular lesions or proteinuria, also had significantly elevated mesangial AHIgG levels. Our results suggest that increased mesangial macromolecular flux may occur independent of altered glomerular permselectivity changes and proteinuria and appears to be related to glomerular hyperfiltration rather than glomerular hypertension. Further, glomerular mesangial sclerosis may not be the direct result of increased mesangial macromolecular flux.

Perinatal radiation-induced renal damage in the beagle.

The developing perinatal kidney is particularly sensitive to radiation. The pathogenesis of the radiation-induced lesion is related to the destruction of outer cortical developing nephrons and direct radiation injury with secondary hemodynamic alterations in remnant nephrons. In this study, which is part of a life span investigation of the effects of whole-body gamma radiation during prenatal and early postnatal life, dogs were given 0, 0.16, 0.83, or 1.25 Gy irradiation at either 55 days postcoitus or 2 days postpartum and were examined morphometrically and histopathologically at 70 days of age. Although irradiated dogs showed no reduction in the total number of nephrons per kidney, there was a significant increase in the total number and relative percentage of immature, dysplastic glomeruli. In addition, deeper cortical glomeruli of irradiated kidneys exhibited mesangial sclerosis similar to that associated with progressive renal failure in our previous studies. These findings are in accord with those reported at doses of 2.24 to 3.57 Gy and demonstrate that the perinatal kidney is affected by radiation doses much lower than previously demonstrated.

Effects of dietary protein and captopril on glomerular permselectivity in rats with unilateral nephrectomy.

Proteinuria and progressive glomerulosclerosis are commonly associated with nephron loss. We studied the pathogenesis of these lesions by examining the role of changes in specific glomerular capillary wall permeability properties in uninephrectomized rats. The development of altered capillary permselectivity to macromolecules and loss of glomerular basement membrane anionic charge were measured by the dextran fractional clearance and ferritin tracer probe methods, respectively. In addition, the protective effect of dietary protein restriction and an angiotensin I-converting enzyme inhibitor (captopril) were studied in eight groups of male Sprague-Dawley rats. Four groups of rats underwent sham-nephrectomy or left nephrectomy and were fed an 8.5% protein diet (sham-nephrectomy and low protein, nephrectomy and low protein) or a 30% protein diet, respectively (sham-nephrectomy and high protein, nephrectomy a high protein). Four other groups of rats underwent sham-nephrectomy or left nephrectomy and were treated with captopril (50 mg/kg/day) while receiving a 8.5% protein diet (sham-nephrectomy, low protein and captopril, nephrectomy, low protein and captopril) or a 30% protein diet, respectively (sham-nephrectomy, high protein and captopril, nephrectomy, high protein and captopril). Rats were nephrectomized at 21 days of age and were functionally tested and sacrificed at 7 months of age. The nephrectomy and high protein rats had significantly greater proteinuria and higher fractional clearance of neutral dextrans in the 30 to 42 A range compared with that of sham-nephrectomy and high protein, nephrectomy and low protein, and nephrectomy, high protein and captopril rats. The nephrectomy and high protein rats also had a significantly lower labeling of the glomerular basement membrane with cationic ferritin tracer molecules compared with the nephrectomy and low protein and nephrectomy, high protein and captopril rats. Of the eight treatment groups, the nephrectomy and high protein rats had the most severe glomerular lesions. In general, nephrectomized rats fed low dietary protein and nephrectomized rats treated with captopril had significantly less proteinuria, glomerular lesions, and milder changes in the glomerular capillary wall porosity and glomerular basement membrane anionic charge.(ABSTRACT TRUNCATED AT 400 WORDS)

A technique for estimating progression of chronic renal failure in the dog.

A simple method for estimating the rate of progression of chronic renal failure was evaluated in 11 dogs. The plot of the reciprocal of the serum creatinine concentration vs age declined linearly, and projection of the regression line to the abscissa accurately predicted each dog's age at the time of death attributable to renal failure. The linear decline of the reciprocal of the serum creatinine concentration vs age indicated that nephrons may be lost at a constant rate in dogs with chronic renal failure. Changes in the slope of this line may provide a means of evaluating response to treatment.

Renal functional relationships in dogs with glomerulopathies.

Glomerular filtration rate, effective renal plasma flow, and filtration fraction were determined by measuring plasma disappearance of [14C] inulin and [3H]tetraethylammonium bromide after a single IV bolus injection was given to 8 dogs with membranous nephropathy, renal glomerulosclerosis, or renal amyloidosis. Glomerular filtration rate was decreased in the 8 dogs. Effective renal plasma flow was within reference values in 1 dog, increased in 1 dog, and decreased in 6 dogs. Filtration fraction was within reference values in 2 dogs and decreased in 6 dogs. The glomerular filtration rate also was estimated by the endogenous creatinine clearance technique and was decreased in the 8 dogs with glomerulopathies.

Membranous nephropathy in the dog.

Membranous nephropathy, a disease syndrome characterized by severe proteinuria and often accompanied by the nephrotic syndrome, was identified in 29% of a population of 46 proteinuric dogs. Renal lesions were characterized by the presence of subepithelial immunoglobulin deposits distributed diffusely along the glomerular capillary wall. Advanced stages were associated with progressive thickening of capillary basement membranes and incorporation of the immune deposits. These changes were followed by either glomerulosclerosis or recovery. Characteristic morphologic stages were correlated with clinical pathologic findings which showed that the level of proteinuria, hypoalbuminemia, and consequent nephrotic syndrome was most severe in the initial stages of membranous nephropathy while the level of azotemia increased in the more advanced stages of the syndrome.

Functional and morphologic damage in the neonatally irradiated canine kidney.

Perinatal irradiation of the developing kidney results in progressive glomerulosclerosis (PGS) and renal failure. This syndrome may result from direct radiation damage to mature deep cortical nephrons and/or nephron functional adaptations resulting from outer cortical nephron ablation. Beagle dogs received single, whole-body exposures (330 R) to 60Co gamma radiation at 4 days of age (IR4) to study the combined effects of direct radiation damage and nephron loss, or at 30 days of age (IR30) to study the effects of renal irradiation alone. To study the effects of nephron loss alone, dogs underwent unilateral nephrectomy (UN4) or superficial hyperthermic renal ablation (HY4) at 4 days of age. Nephron loss due to irradiation (IR4) and partial renal ablation (UN4 and HY4) was associated with compensatory nephron hypertrophy and increased single nephron glomerular filtration rate (SNGFR), while irradiation at 30 days resulted in transitory decreased SNGFR. Similar degrees of PGS occurred in IR4 dogs which experienced both irradiation and loss of nephrons and UN4 and HY4 dogs which experienced only loss of nephrons. PGS of lesser severity also occurred in IR30 dogs. These findings indicate that PGS associated with perinatal renal irradiation results from direct radiation damage to deep cortical nephrons and compensatory functional changes occurring in response to loss of renal mass.

In vivo RNA synthesis of the hearts of adriamycin-treated rats.

Data are presented which demonstrate the effect of both acute and chronic Adriamycin treatment on myocardial RNA synthesis in vivo. The results suggest that the inhibition of RNA synthesis is a transient effect following both types of treatment and that the degree and duration of this effect is dose dependent. The data further demonstrate that Adriamycin dose not alter the turnover rate of RNA and that both messenger RNA and ribosomal RNA are affected. These results, interpreted in conjunction with pharmacokinetic data, permit speculation on the relationship between acute and chronic Adriamycin treatment as well as cellular ramifications with regard to the protracted, dose-dependent cardiomyopathy.

Cardiotoxicity and comparative pharmacokinetics of six anthracyclines in the rabbit.

Six anthracycline antibiotics with demonstrated antitumor activity in human or experimental tumor systems were studied. The purpose of this investigation was to compare the cardiotoxic potential of these compounds and to characterize the myocardial pharmacokinetics in order to provide a possible explanation for differences in cardiotoxicity. Groups of rabbits received i.v. injections of drug at maximally tolerated treatment doses with respect to lymphohematopoietic toxicity for periods of 11 or 16 weeks and were evaluated histopathologically for the development of myocardial damage. Following a single i.v. administration of the different anthracyclines to rabbits, the amount of parent drug and metabolites accumulating in the heart at various times was determined by high-pressure liquid chromatography and fluorometry. Adriamycin (ADR), daunorubicin (DNR), and detorubicin produced similar severe cardiomyopathy with frequent congestive heart failure at approximately equal dose levels. Three additional antibiotics, rubidazone and the N-L-leucyl derivatives of ADR and DNR (N-L-leucyl-adriamycin and N-L-leucyl-daunorubicin), produced significantly less severe lymphohematopoietic toxicity, thus permitting the administration of 3 to 3.5 times the ADR and DNR treatment doses. Chronic treatment with these anthracyclines also resulted in significantly less cardiomyopathy, especially in the case of N-L-leucyl-daunorubicin and rubidazone. This reduced cardiomyopathy correlated with lower total myocardial drug accumulation but, more importantly, with lower amounts of DNR or ADR accumulation in the heart. These findings suggest that the degree of anthracycline myocardial toxicity may be directly related to the relative qualitative and quantitative accumulation of drug metabolites in the myocardium.

Progressive glomerulosclerosis and renal failure following perinatal gamma radiation in the beagle.

The renal effects of whole body irradiation in the perinatal period were studied in the dog. Ninety-three dogs received a single sublethal exposure in the range of 270 to 435 R in either late gestation (55 days postcoitus) or early postnatal life (2 days postpartum) and were sacrificed at 70 days, 2, or 4 years of age. Early renal lesions in 70-day-old irradiated dogs were characterized by arrested glomerular maturation and degeneration resulting in reduced functional renal mass. Mature glomeruli exhibited mesangial proliferation. At 2 and 4 years of age, surviving irradiated dogs exhibited severe renal disease associated with progressive glomerular damage which was characterized by mesangial proliferation and compression of capillary lumina, epithelial degeneration and focal capsular adhesions, and ultimately obliterative glomerulosclerosis. Twenty-one of the 93 irradiated dogs died in renal failure before 4 years of age with advanced glomerulosclerosis. The pathogenesis of this progressive renal lesion may be related to the interaction of three specific factors. These include (1) the effect of direct radiation damage to mature kidney components; (2) the loss of outer cortical nephrons resulting in increased work load of the surviving nephrons; and (3) the effect of compensatory hypertrophy related to the loss of renal parenchyma as the rapid growth rates associated with kidney maturation.