Proximal Tubular Epithelium Research Articles

Intravenous single dose toxicity of iodixanol, a new nonionic iso-osmolar contrast medium, in mice, rats and monkeys

The single-dose intravenous toxicities of iodixanol, a new nonionic iso-osmolar contrast medium, were investigated in mice, rats and monkeys. The LD50 values were estimated to be 17.9 gI/kg for male mice and 16.2 gI/kg for female mice, 18.8 gI/kg for male rats and 22.0 gI/kg for female rats, and more than 10.0 gI/kg for monkeys. There was no marked sex difference in mice or rats, nor any significant difference observed between these two rodent species. Decrease in spontaneous locomotor activity, ptosis, respiratory depression and abdominal posture were observed in many mice and rats. These signs disappeared mostly by 8 days after dosing in surviving animals. Death occurred between immediately and 4 days after dosing in mice, and between immediately and 14 days after dosing in rats. Transient depression of body weight gain was observed in the surviving mice and rats by 7 days after dosing. Histological examinations revealed congestion or hemorrhage in the renal medulla, vacuolation or necrosis of the renal proximal tubular epithelium in mice and rats that died and vacuolation of the renal proximal tubular epithelium in surviving rats. There were no significant treatment-related changes in the laboratory and pathological examinations in monkeys.

Nephrotoxicity of cyclosporin A and FK506: inhibition of calcineurin phosphatase.

Cyclosporin A (CsA; 50 mg/kg) and Fujimycine (FK506; 5 mg/kg), but not the related macrolide immunosuppressant rapamycin (5 mg/kg), caused a reduction of glomerular filtration rate, degenerative changes of proximal tubular epithelium, and hypertrophy of the juxtaglomerular apparatus in male Wistar rats when given for 10 days. The molecular mechanisms of CsA and FK506 toxicity were investigated. Cyclophilin A and FK506-binding protein, the main intracytoplasmic receptors for CsA and FK506, respectively, were each detected in renal tissue extract. In the kidney, high levels of immunoreactive and enzymatically active calcineurin were found which were inhibited by the immunosuppressants CsA and FK506, but not by rapamycin. Finally, specific immunophilin-drug-calcineurin complexes formed only in the presence of CsA and FK506, but not rapamycin. These results suggest that the nephrotoxic effects of CsA and FK506 is likely mediated through binding to renal immunophilin and inhibiting calcineurin phosphatase.

Induced regenerative cell proliferation in livers and kidneys of male F-344 rats given chloroform in corn oil by gavage or ad libitum in drinking water

These studies were designed to establish the dose response relationships for the induction of cytolethality and regenerative cell proliferation in the liver and kidneys of male F-344 rats given chloroform by gavage or in drinking water. Rats were administered oral doses of 0, 10, 34, 90 or 180 mg/kg/day chloroform dissolved in corn oil by gavage for 4 days or for 5 days/week for 3 weeks. A second group of rats was given chloroform ad libitum in the drinking water at concentrations of 0, 60, 200, 400, 900 or 1800 ppm for 4 days or 3 weeks. Bromodeoxyuridine (BrdU) was administered via an implanted osmotic pump 3.5 days prior to necropsy to label cells in S-phase. Cells having incorporated BrdU were visualized in tissue sections immunohistochemically and the labelling index (LI) evaluated as the percentage of S-phase cells. Rats treated with 90 or 180 mg/kg/day by gavage for 4 days had mild to moderate degeneration of renal proximal tubules and centrilobular hepatocytes. These alterations were absent or slight after 3 weeks of treatment. LI were increased in the kidney cortex only in the rats treated with 180 mg/kg/day for 4 days. A dosedependent increase in LI was seen in rat liver after 4 days of treatment with 90 and 180 mg/kg/day by gavage, but the LI remained elevated after 3 weeks of treatment only at the 180 mg/kg/day dose. When chloroform was administered in the drinking water, no microscopic alterations were seen in the kidneys after 4 days of treatment. As a general observation, rats treated for 3 weeks with 200 ppm chloroform and greater had slightly increased numbers of focal areas of regenerating renal proximal tubular epithelium and cell proliferation than were noted in the controls, but no clear dose response relationship was evident. However, the overall renal LI was not increased at any dose or time point. Similarly, only mild hepatocyte vacuolation was observed in rats given 1800 ppm chloroform in the water for 3 weeks with no increase in the hepatic LI at any time point, even though the rats were consuming chloroform at a rate of 106 mg/kg/day at the 1800 ppm drinking water concentration. These data indicate more severe hepatic and renal toxicity when chloroform is administered by gavage than in the drinking water and a different pattern of regenerative proliferation in the kidney. Thus, the impact that different methods and rates of chloroform administration have on tissue dosimetry and tissue response must be understood in interpreting toxic outcomes in rodents and extrapolating potential effects to humans.

Thiabendazole (TBZ) nephrotoxicity and recovery in ICR adult mice

The nephrotoxicity and recovery following administration of thiabendazole (TBZ) were investigated in ICR adult mice. A single oral administration of TBZ (500–2000 mg/kg body wt.) caused a dose-dependent proximal tubular necrosis in the kidney and increase in serum urea nitrogen 24 h after dosing. These changes were marked in mice of high dose groups (1000 or 2000 mg TBZ/kg body wt.). The time course of changes on kidney of mice treated with 1000 or 2000 mg TBZ/kg body weight were examined at 1, 2, 3, 5, 7 or 10 days after dosing. Light microscopy showed necrosis of proximal convoluted tubules from 1 day after dosing. Tubular necrosis was extensive 2 or 3 days after dosing. Partial regeneration from tubular necrosis was seen 3 days after dosing, and substantial regeneration had occured from 5 days after dosing. Thus, TBZ-induced renal injury was most severe at 2 or 3 days after dosing and was followed by regeneration. Electron microscopy showed swelling of mitochondria in the proximal tubular epithelium at 1 day after dosing. The pathological changes were correlated with the changes in urinalysis, serum urea nitrogen concentration and kidney weight.

Iron accelerates while magnesium inhibits nickel-induced carcinogenesis in the rat kidney

Effects of magnesium basic carbomate (MgCarb) and metallic iron powder (Fe 0) on nickel subsulfide (Ni 3S 2)-induced carcinogenesis were studied in kidneys of male F344/NCR rats. The rats, 20–40/group, received functions of Ni 3S 2 alone (62 μmol Ni or with equimolar doses of MgCarb or Fe 0 into the renal cortex of each pole of the right kidney. Control rats were given MgCarb, Fe 0, or 0.1 ml of 50% aqueous glycerol, the injection vehicle. Final incidence of renal tumors 2 years later the injection of Ni 3S 2 alone or mixed with FE 0 was 60%. However, rats given Ni 3S 2 + Fe 0 developmed renal tumours much more rapidly. In contrast, the incidence of renal tumors in rats given Ni 3S 2 + MgCarb was only 20% ( P < 0.01 vs. Ni 3S 2 alone). No kidney tumors were observed in the control rats. Between weeks 4 and 32 post injection Ni 3S 2 alone caused erythrocytes. This effect was attenuated by Fe 0, but not by MgCarb. Hence, there is no firm correlation between carcinogenecity activity of nikel and its ability to induced erythropoiesis. All kidney tumors were of mesenchymal cell origin and resembled the sarcomatous variant of the classic rat renal mesenchymal tumor. Some of them metastatized to the lungs and other organs. In 3–35 days post-injection , kidneys of rats treated with Ni 3S 2 alone showed moderate to extensive necrosis, inflammation, fibrosis, and degenerative and regenerative proliferative changes in the proximal tubular epithelium at the injection site. Similar, but more severe and multifocal changes were observed in the kidneys of Ni 3S 2 + Fe 0-treated rats. The necrosis was less severe in kidneys injected with Ni 3S 2 + MgCarb, but fibrosis and degenerative and regenerative changes in proximal tubular epithelium were similar to those observed in other treatment groups. Ni 3S 2 deposits were seen inside macropahges and proximal tubular epithelial cells of Ni 3S 2 and Ni 3S 2 + Fe 0-treated kidneys more frequently than in Ni 3S 2 + MgCarb-treated kidneys. Thus, magnesium antagonizes nickel carcinogenesis in the rat kidney while iron tends to enhance it. This result may be related to respectively attenuating or enhancing effects of magnesium and iron on the inflammatory response to Ni 3S 2.

Uric acid degrading enzymes, urate oxidase and allantoinase, are associated with different subcellular organelles in frog liver and kidney

On the basis of differential and density gradient centrifugation studies, the site of the uric acid degrading enzymes, urate oxidase and allantoinase, in amphibia was previously assigned to the hepatic peroxisomes. Using specific antibodies against frog urate oxidase and allantoinase, we have undertaken an immunocytochemical study of the localization of these two proteins in frog liver and kidney, and demonstrate that whereas urate oxidase is present in peroxisomes, allantoinase is localized in mitochondria. Urate oxidase and allantoinase were detected by immunoblot analysis in both frog liver and kidney. The subcellular localization of these two enzymes was ascertained by Protein A-gold immunocytochemical staining of Lowicryl K4M-embedded tissue. Peroxisomes in frog liver parenchymal cells and kidney proximal tubular epithelium contained a semi-dense subcrystalloid core, which was found to be the exclusive site of urate oxidase localization. Allantoinase was detected within mitochondria, but not in peroxisomes of hepatocytes or proximal tubular epithelium. No allantoinase was detected in the mitochondria of nonhepatic parenchymal cells in liver and of the cells lining the distal convoluted tubules of the kidney. These results demonstrate that, unlike rat kidney peroxisomes which lack urate oxidase, peroxisomes of frog kidney contain this enzyme. Contrary to previous assumptions, these studies also clearly establish that urate oxidase and allantoinase, the first two enzymes involved in uric acid degradation, are localized in different subcellular organelles in frog liver and kidney.

Promoting effects of ethinyl estradiol on development of renal proliferative lesions induced by N-nitrosobis (2-oxopropyl)amine in female Syrian golden hamsters.

The modulating effects of female sex hormones, ethinylestradiol and levonorgestrel, on the development of renal proliferative lesions after initiation with N-nitrosobis(2-oxopropyl)amine (BOP) were investigated. Three groups of female Syrian golden hamsters, each comprising 30 animals, were given four weekly s.c. injections of BOP (10 mg/kg body weight) and then fed diet containing 1 ppm ethinylestradiol (group 1: BOP/EE), diet containing 10 ppm levonorgestrel (group 2) or basal diet (group 3) for the next 27 weeks. As hormone controls, two groups of 20 female hamsters each received diet containing 1 ppm ethynylestradiol (group 4) and 10 ppm levonorgestrel (group 5) from week 3 for 27 weeks without the prior initiation treatment. The severity of diffuse anisokarya, characterized by varied nuclear size and the incidence of dysplasias of the proximal tubular epithelia induced by BOP, were significantly increased in the BOP/EE group, indicating the promoting effects of the hormone. In the renal dysplastic lesions (small-cluster, cystic, clear-cell and acidophilic cell types), adenomas and nephroblastomas, increases in the numbers of argyrophilic proteins associated with nucleolar organizer regions (NOR) in the nucleus, suggesting a high proliferative activity, were seen in dysplasia of acidophilic cell types and adenomas. In addition, the number of bizarre NOR per nucleus was significantly higher in adenomas than in dysplasias and highest in nephroblastomas. This morphological change in NOR should therefore be a useful parameter for the diagnosis of malignancy of renal tumors.

The growth hormone insulin-like growth factor axis in kidney revisited

Studies characterizing actions of growth hormone (GH) and insulin-like growth factors (IGF) in kidneys of adult and developing animals and humans have provided a good deal of insight into the functions of these peptides. Although certain of the actions may be mediated directly by GH, most appear to result from effects of GH to increase levels of circulating IGF or IGF produced in kidney. In addition to GH, epidermal growth factor (EGF) enhances the renal synthesis of IGF-I. Enhancement of renal IGF-I expression is GH independent in compensatory hypertrophy. Stimulation of kidney IGF-I production also occurs in diabetes mellitus. Renal IGF-I production is elevated in these settings in the absence of changes in circulating IGF-I, consistent with a causative role of renal IGF-I for the accompanying increased glomerular filtration rate and kidney growth. Actions of IGF in kidney are initiated following binding of peptides to specific receptors. Receptor number may be altered during compensatory growth and in diabetes mellitus. In addition to IGF, several IGF binding proteins (IGFBP) are produced in kidney and are likely to both inhibit and enhance the actions of IGF in different circumstances through sequestration of peptides and regulation of peptide interactions with their receptors. Administration of IGF-I to rats following acute ischemic injury hastens the recovery of normal renal function and accelerates the regeneration of the damaged proximal tubular epithelium. IGF-I increases the glomerular filtration rate in humans with normal and reduced functional kidney mass. These findings establish the potential for use of this peptide as a therapeutic agent in the settings of acute and chronic renal failure.

Quantitation of Glutathione Transferase-Pi in the Urine by Radioimmunoassay

A radioimmunoassay procedure for the quantitation of glutathione transferase-pi was developed in order to determine the levels of this protein in human urine. The enzyme was isolated from human placenta with a purification factor of 366 (compared to the original high-speed supernatant fraction), and upon gel electrophoresis, only a single band was seen. Polyclonal antisera were subsequently raised in rabbits and found to be suitable for a radioimmunoassay. Glutathione transferase-pi was localized immunohistochemically to the cells of the distal tubules, the thin loop of Henle and the collecting ducts in the kidney. In contrast, the alpha-isoenzyme was localized exclusively in the proximal tubular epithelium. Samples of urine from healthy individuals contained about 6 ng of the pi-transferase/ml. The method proved to be specific for glutathione transferase-pi, and no cross-reaction with the alpha- or mu-transferase or with other proteins occasionally appearing in urine occurred. The protein was quite stable upon storage and insensitive to variations in the urine pH. Thus, it appears that glutathione transferase-pi can be conveniently quantitated by radioimmunoassay and changes in the concentration of this protein in human urine thus monitored.

HK-2: An immortalized proximal tubule epithelial cell line from normal adult human kidney

Studies assessing mechanisms of proximal tubular cell (PTC) physiology and pathophysiology increasingly utilize cell culture systems to avoid the complexity of whole organ/whole animal experiments. However, no well-differentiated PTC line derived from adult human kidney currently exists. Therefore, the goal of this research was to establish such a line by transduction with human papilloma virus (HPV 16) E6/E7 genes. A primary PTC culture from normal adult human renal cortex was exposed to a recombinant retrovirus containing the HPV 16 E6/E7 genes, resulting in a cell line designated HK-2 (human kidney-2) which has grown continuously in serum free media for more than one year. HK-2 cell growth is epidermal growth factor dependent and the cells retain a phenotype indicative of well-differentiated PTCs (positive for alkaline phosphatase, gamma glutamyltranspeptidase, leucine aminopeptidase, acid phosphatase, cytokeratin, alpha 3 beta 1 integrin, fibronectin; negative for factor VIII-related antigen, 6.19 antigen and CALLA endopeptidase). Furthermore, HK-2 cells retain functional characteristics of proximal tubular epithelium (Na+ dependent/phlorizin sensitive sugar transport; adenylate cyclase responsiveness to parathyroid, but not to antidiuretic, hormone). The E6/E7 genes are present in the HK-2 genome, as determined by PCR. To assess its potential usefulness as a tool for studying injury and repair, HK-2 cells were exposed to a toxic concentration of H2O2 +/- iron chelation (deferoxamine) or hydroxyl radical scavenger (Na benzoate) therapy. Only the former blocked H2O2 cytotoxicity, reproducing results previously obtained with freshly isolated rat proximal tubular segments. In conclusion, an immortalized adult human PTC line has been established by transduction with HPV 16 E6/E7 genes. It appears to be well-differentiated on the basis of its histochemical, immune cytochemical, and functional characteristics, and it can reproduce experimental results obtained with freshly isolated PTCs. Thus, this new PTC line could have substantial research application.

Glomerulocystic kidney diseaseの成人例

A 56-year-old female presented with end-stage renal disease. A CT scan of her kidneys demonstrated that the density of the renal parenchyma was quite low as compared with normal kidneys, and that corticomedullary demarcation was obscured. Magnetic resonance imaging (MRI) disclosed low intensity of the kidneys in T1-weighed images, and high intensity in T2-weighed images. In order to elucidate the etiology of her kidney disease, open renal biopsy was performed. The kidney surface was covered with numerous cysts with a diameter of less than 3 mm. Biopsy specimens from the cortical surface showed multiple cystic lesions. Serial sections of more than 200 slices of the biopsy material demonstrated that traces of collapsed glomeruli were present in most of the cysts. On electron microscopy, some epithelial cells lining the cysts were found to be round-shaped and contained a substantial amount of mitochondria, suggesting proximal tubules. These histological findings were compatible with glomerulocystic kidney disease (GCKD). An adult case of GCKD has rarely been reported, but the CT scan as well as MRI of the kidneys appeared to complement the diagnosis of GCKD. Although the cysts of GCKD have been considered to be dilatations of the Bowman's capsules, our observation suggested that part of the cells lining the cysts consisted of proximal tubular epithelium.

Hepatocyte growth factor accelerates recovery from acute ischemic renal injury in rats

Effects of hepatocyte growth factor (HGF) administration were examined in a model of acute ischemic renal injury induced by bilateral renal artery occlusion in rats. Compared with rats administered vehicle, rats administered 20 micrograms HGF subcutaneously 30 min postischemia had significantly lower serum creatinine and blood urea nitrogen levels over the course of 7 days postocclusion, enhanced insulin clearances measured on day 2 postocclusion, reduced mortality, and much less injury evident by examination of kidney histologies 7 days postinjury. The tubular regeneration that occurred postischemic injury was reflected by increased incorporation of 5-bromo-2'-deoxyuridine (BrdU) in cortical tubular epithelium compared with incorporation in kidneys from noninjured rats. HGF enhanced BrdU incorporation compared with vehicle, indicating enhanced mitogenesis. The weight loss that occurs postischemic injury was not ameliorated by the dose of HGF we employed. We conclude that administration of HGF postischemic injury to rats stimulates the recovery of normal kidney function and the regeneration of proximal tubular epithelium.

Ly-6 in kidney is widely expressed on tubular epithelium and vascular endothelium and is up-regulated by interferon gamma.

Ly-6 is a multigene family of murine polymorphic cell membrane proteins that are glycosydlphosphatidylinositol anchored, widely expressed on lymphoid tissue, and homologous to the recently described human CD59. An unexpected feature of Ly-6 is its high level of expression in the kidney. This renal expression and its interferon (IFN)-gamma inducibility in murine strains expressing different Ly-6 haplotypes were studied with monoclonal antibodies and cDNA probes that recognize Ly-6A/E and Ly-6C. Ly-6 expression was much more extensive in the kidney than in other parenchymal organs. Ly-6A.1/E.2 was extensively expressed on vascular endothelium and on tubular epithelium, particularly in the distal nephron. Pattern of expression differed between strains expressing A and E alleles. Ly-6C was not detected by monoclonal antibodies but was detected by oligonucleotide-specific probes. Treatment with recombinant IFN-gamma or IFN-inducing agents increased Ly-6 expression markedly, particularly on the luminal aspect of the proximal tubular epithelium, where Ly-6A/E became prominent. This luminal expression is typical for glycosydlphosphatidylinositol-anchored proteins but contrasts with that of other molecules, such as major histocompatibility classes I and II, which are generally expressed on the basolateral surface of the tubular epithelium. Up-regulation occurred within 6 h of IFN-gamma treatment and returned to normal by 48 h. Similar up-regulation of Ly-6 was seen in murine lupus nephritis and in mercuric chloride nephropathy. The characteristics of renal Ly-6, such as its IFN-gamma responsiveness, endothelial and tubular expression, polymorphism, strong antigenicity, and possible allelic regulation, make it a candidate to be a target molecule in alloresponses. The renal expression of Ly-6 is similar to that of CD59 in the human kidney, supporting the suggestion that these proteins are closely related.

Comparative modulating effects of captopril, diltiazem, dietary calcium and pyridoxal-5′-phosphate on gentamicin-induced nephrotoxicity in the rat

1. Nephrotoxicity was induced in rats by injecting gentamicin intramuscularly (i.m.) at a dose of 80 mg/kg/day for 6 days. Treated animals demonstrated a typical pattern of aminoglycoside nephrotoxicity characterized histopathologically by necrosis of proximal tubular epithelium, and biochemically by increased serum creatinine and urea concentrations. Reduced glutathione (GSH) concentration in renal cortex was significantly decreased by gentamicin. 2. Simultaneous treatment of rats with gentamicin and either captopril or diltiazem significantly potentiated the gentamicin-induced increases in serum creatinine and urea and did not significantly affect the gentamicin-induced decrease in cortical GSH concentration. 3. Concomitant treatment with gentamicin and either Ca 2+ or pyridoxal-5′-phosphate decreased serum urea level, did not significantly affect serum creatinine concentration, and significantly increased cortical GSH concentration in comparison to the values of these parameters following gentamicin treatment. 4. Histopathologically, the severity of gentamicin-induced renal damage was exacerbated by captopril, and even more so by diltiazem. Simultaneous treatment with gentamicin and either Ca 2+ or pyridoxal-5′-phosphate produced only mild focal atrophy of renal tubular epithelium. Control rats had apparently normal histology. 5. In conclusion, captopril and diltiazem, at the doses used, significantly potentiated gentamicin-induced nephrotoxicity to a broadly similar extent. Although Ca 2+ and pyridoxal-5′-phosphate, at the doses used, reduced significantly the severity of some of the manifestations of nephrotoxicity, they were equally ineffective in completely preventing the development of nephrotoxicity.

The growth hormone insulin-like growth factor axis in kidney revisited

Studies characterizing actions of growth hormone (GH) and insulin-like growth factors (IGF) in kidneys of adult and developing animals and humans have provided a good deal of insight into the functions of these peptides. Although certain of the actions may be mediated directly by GH, most appear to result from effects of GH to increase levels of circulating IGF or IGF produced in kidney. In addition to GH, epidermal growth factor (EGF) enhances the renal synthesis of IGF-I. Enhancement of renal IGF-I expression is GH independent in compensatory hypertrophy. Stimulation of kidney IGF-I production also occurs in diabetes mellitus. Renal IGF-I production is elevated in these settings in the absence of changes in circulating IGF-I, consistent with a causative role of renal IGF-I for the accompanying increased glomerular filtration rate and kidney growth. Actions of IGF in kidney are initiated following binding of peptides to specific receptors. Receptor number may be altered during compensatory growth and in diabetes mellitus. In addition to IGF, several IGF binding proteins (IGFBP) are produced in kidney and are likely to both inhibit and enhance the actions of IGF in different circumstances through sequestration of peptides and regulation of peptide interactions with their receptors. Administration of IGF-I to rats following acute ischemic injury hastens the recovery of normal renal function and accelerates the regeneration of the damaged proximal tubular epithelium. IGF-I increases the glomerular filtration rate in humans with normal and reduced functional kidney mass. These findings establish the potential for use of this peptide as a therapeutic agent in the settings of acute and chronic renal failure.

Immunohistochemical localization of rat angiotensin II AT1 receptor

To study receptors for angiotensin II, polyclonal rabbit anti-peptide antisera were prepared against the peptide QDDCPKAGRHC corresponding to amino acids 15-24 of the rat AT1A and AT1B receptors. Western analysis of rat tissues showed a major band of approximately 43 kDa. The antisera immunoprecipitated AT1-receptor protein produced in vitro. Immunohistochemical analysis of rat tissues showed intense staining of arterial and arteriolar smooth muscle. Other tissues that contained AT1-receptor protein included hepatocytes, the zona glomerulosa of the adrenal gland, and the smooth muscle of the bronchus, gut, ureter, and epididymis. In the kidney, intense staining was observed in all small arteries and arterioles. Both afferent and efferent arterioles contain approximately equal intensities of immunoreactive AT1 protein. The inner stripe of the outer medulla has a moderate level of receptors within thick ascending limb epithelium. Proximal tubular epithelium also expresses receptor protein. Glomerular immunoreactive AT1 protein is found within mesangial cells and varies in intensity among different rat strains. Lewis and Wistar rats demonstrated moderate glomerular staining, whereas the CD and Sprague-Dawley strains showed lesser levels of reactivity. The fact that glomerular mesangial cells are the primary locus of angiotensin II action within the glomerulus.

Transforming Growth Factor‐α Expression of Renal Proximal Tubules in Wistar Rats Treated with Ferric and Aluminum Nitrilotriacetate

A high incidence of renal adenocarcinoma has been observed in rats treated with ferric nitrilotriacetate (Fe‐NTA) but not in rats treated with aluminum nitrilotriacetate (Al‐NTA). Transforming growth factor (TGF)‐α is one of the several cytokines that is known to be expressed in human and rat renal adenocarcinomas. However, its role in neoplastic transformation is still questionable. Therefore, we investigated the effect of repeated Fe‐NTA and Al‐NTA administration on renal TGF‐α expression. Male Wistar rats were given Fe‐NTA (n = 16, 5–10 mg FeAg) and Al‐NTA (n = 19, 1–2 mg Al/kg) i.p., three times a week for 3 or 12 weeks. Another group of rats (n=4) was given Fe‐NTA (5–10 mg FeAg) three times a week for 12 weeks and then left untreated for one year. Immunoreactivity for TGF‐α was positive in the collecting ducts and on the apical surface of proximal tubules in the outer stripe of the outer medulla in all the animals including NTA‐injected control animals. However, TGF‐α immunoreactivity in the regenerative proximal tubular epithelium was observed only in the animals treated with Fe‐NTA for 12 weeks. Northern blot analysis also showed expression of TGF‐α mRNA only in animals treated with Fe‐NTA for 12 weeks. The expression of TGF‐α mRNA in the kidney was stronger than that in the liver or brain, TGF‐α was also positive in renal cell carcinoma found in animals treated with Fe‐NTA for 12 weeks and left untreated for one year. These results suggest that TGF‐α expression may play an important role in renal carcinogenesis and that it may be a sensitive marker during the induction stage of renal cell carcinoma.

Acute toxicity of cadmium in rats with or without cadmium pretreatment.

The acute toxicity of cadmium (Cd) in male rats was examined with or without Cd pretreatment. Firstly, the metallothionein (MT) contents in the liver and kidney after Cd exposure (2.0 mg/kg, i.v.) were determined. The MT contents in the liver increased immediately to a peak (36.0 +/- 5.5 n mol/g wet tissue) 2 days after Cd exposure and were 55-fold higher than that at 0 day (0.64 +/- 0.25 n mol/g wet tissue). On the other hand, the MT contents in the kidney increased slightly but steadily for 14 days after Cd exposure. In the study for comparison of Cd-induced toxicity, the LD50 value of the Cd-pretreatment group (Group II) was approximately 2-fold higher than that of the non-pretreatment group (Group I). In microscopic findings, differences between rats in Group I and Group II were recognized in the kidney. Cytoplasmic vacuolation of the proximal tubular epithelium in the kidney was observed in Group I, while degeneration or coagulative necrosis in the proximal tubular epithelium was observed in some rats in Group II in addition to the cytoplasmic vacuolation. Because the toxic changes other than in the kidney in Group II were almost equal to or less than that in Group I, in spite of the doubled dosage of Cd, the toxic effects of Cd, except on the kidneys, were considered to be reduced by the pretreatment with Cd.

同種異系植皮に対するシクロスポリン軟膏の局部投与の薬理効果

In this study, we investigated the pharmacologic effect of topical cyclosporin A (CSA) cintment on skin allograft from Lewis rats to Fischer rats. The 10% CSA ointment was prepared and applicated. Untreated allografts were rejected in 11.0±1.0 days, but long term graft survival (26.3±2.7 days) was significantly seen with continuous topical 10% CSA ointment treatment for 12 days at 15 mg/rat/ day (P<0.001) . The mean survival time of allograft receiving topical 10% CSA ointment was significantly (P<0.05) even longer than the allografts receiving 4 mg/kg/day i.v. for 15 days (21.7±4.4 days) .Light microscopy revealed the deposition of PAS positive granules in and exfoliation of proximal tubular epithelium in rats receiving topical CSA ointment. These changes were observed likewise in untreated rats. So it may be not characteristic of CSA nephrotoxicity.These results suggest that topical CSA ointment may play an important role in application of allcgraft to cover skin defects caused by severe burn injury.

Effects of angiotensin II on proximal tubular cells stably transfected with the c-mas oncogene.

Angiotensin II (ANG II) normally induces cellular hypertrophy in proximal tubular epithelium by engaging receptor systems that use a G-protein-signaling mechanism. The c-mas oncogene also encodes part of a superfamily of vasoactive peptide receptor-like moieties that couple to G proteins. To determine whether the stable expression of the c-mas gene might alter or modify the induction of cellular hypertrophy by ANG II in tubular epithelium, a rat c-mas cDNA was cloned into the pSV2 expression vector for use in cell transfection. Scatchard analysis of ANG II binding revealed no significant differences in ANG II receptor number or in the dissociation constant between pSV2mas-transfected or wild-type MCT cells, but rather an increase in the number of receptors not replaceable by known inhibitors. ANG II also induced proliferation in pSV2mas-transfected MCT cells that was not blocked by conventional inhibitors and increased intracellular levels of inositol trisphosphate. ANG II, furthermore, did not increase de novo protein synthesis in pSV2-transfected MCT cells and failed to lower their intracellular concentration of adenosine 3',5'-cyclic monophosphate, both expected parameters of cellular hypertrophy. Our findings demonstrate that expression of c-mas in tubular epithelium can modulate tubular cell phenotype toward proliferation rather than hypertrophy. This effect is likely mediated by a reshuffling of the heterogeneity of ANG II receptors on the cell surface, or perhaps by the emergence of a new ANG II receptor, followed by alterations in the process of signal transduction.