Renal Proximal Tubular Epithelium Research Articles

Characterization of serine palmitoyltransferase in normal human tissues.

Sphingolipids serve as structural elements of cells and as lipid second messengers. They regulate cellular homeostasis, mitogenesis, and apoptosis. Sphingolipid signaling may also be important in various pathophysiologies such as vascular injury, inflammation, and cancer. Serine palmitoyltransferase (SPT) catalyzes the condensation of serine with palmitoyl-CoA, the first, rate-limiting step in de novo sphingolipid biosynthesis. This integral microsomal membrane protein consists of at least two subunits, SPT1 and SPT2. In this study we analyzed the expression of SPT1 and SPT2 in normal human tissues. Strong SPT1 and SPT2 expression was observed in pyramidal neurons in the brain, in colon epithelium, and in mucosal macrophages. However, SPT2 expression was more prominent than SPT1 in the colon mucosal macrophages, the adrenomedullary chromaffin cells and endothelium, and in the uterine endothelium. SPT2 was localized in both nuclei and cytoplasm of the adrenomedullary chromaffin cells, whereas SPT1 was primarily cytoplasmic. These observations link enhanced SPT expression to proliferating cells, such as the lung, stomach, intestinal epithelium, and renal proximal tubular epithelium, and to potentially activated cells such as neurons, chromaffin cells, and mucosal macrophages. A baseline expression of SPT, established by this study, may serve as a measure for aberrant expression in various disease states.

Laminin α1 chain in human renal cell carcinomas and integrin‐mediated adhesion of renal cell carcinoma cells to human laminin isoforms

In human tissues, the laminin (Ln) alpha1 chain shows a restricted and developmentally regulated distribution in basement membranes (BMs) of a subset of epithelial tissues, including those of renal proximal convoluted tubules. The present study investigated the distribution of the Ln alpha1 chain in renal cell carcinomas (RCCs) and oncocytomas as well as in xenografted tumours induced in nude mice with four characterized RCC cell lines. These cell lines were also used in cell adhesion studies with purified laminins. By immunohistochemistry it was found that the Ln alpha1 chain is widely present in the BMs of RCCs, all of the specimens presenting immunoreactivity. High-grade RCCs tended to contain more BM-confined and stromal immunoreactivity than low-grade tumours, none of the grade 3 (G3) carcinomas being negative and all of the metastatic specimens showing partial or overall BM immunoreactivity. Double immunolabelling experiments showed that in RCC BMs but not in vessel walls, the Ln alpha1 chain was co-distributed with Ln alpha5, beta1, and beta2 chains, implying the presence of Ln-1/Ln-3 and Ln-10/Ln-11. In papillary RCCs, the Ln alpha1 chain co-localized with Ln-5. The oncocytomas lacked immunoreactivity for the Ln alpha1 chain. Xenografted tumours induced in nude mice showed BM-like deposition of the Ln alpha1 chain. In cell adhesion studies, mouse and human Ln-1 were equally effective in promoting cell adhesion of all RCC cell lines. For each cell line, Ln-10 and Ln-10/11 were equally effective adhesive substrates, all cell lines adhering more avidly to these laminins than to mouse or human Ln-1. As judged by inhibition assays employing specific integrin antibodies, adhesion of normal human renal proximal tubular epithelial (RPTE) cells and RCC cells from a G1 tumour to human Ln-1 was mediated mainly by alpha(6)beta(1) integrin, while only the G1 RCC cells adhered to mouse Ln-1 by using alpha(6)beta(1) integrin. For adhesion to Ln-10, RPTE cells and RCC cells from a G1 tumour used an unidentified beta(1) integrin. Cells from G3 tumours mainly used an alpha(3)beta(1) integrin complex for adhesion to mouse Ln-1 and to human Ln-1 and Ln-10. For all cells, adhesion to the Ln-10/11 mixture was mediated by an unidentified integrin complex or by other adhesion molecules. These results show that laminin trimers containing the alpha1 chain are, in contrast to oncocytomas, abundant in the BMs of RCCs. This is in keeping with their suggested origin from renal proximal tubular epithelium known for its capacity to produce the Ln alpha1 chain. The results also show that RCC cells utilize complex, mainly integrin alpha(3)beta(1)- and integrin alpha(6)beta(1)-mediated, mechanisms for adhesion to laminins. The adhesion to Ln-1 changes from integrin alpha(6)beta(1) to integrin alpha(3)beta(1) upon increasing malignancy and, especially for Ln-10 and Ln-10/11, other adhesion molecules of non-integrin type may contribute to the adhesion.

The effects of ochratoxin/aluminosilicate interaction on the tissues and humoral immune response of broilers

This study aimed to evaluate the effect of dietary ochratoxin, in the presence or absence of aluminosilicate, on the histology of the bursa of Fabricius, liver and kidneys, and on the humoral immune response of broilers vaccinated against Newcastle disease virus. The exposure of birds to 2 p.p.m. ochratoxin, in the presence or absence of aluminosilicate, reduced their humoral immune response and the number of mitotic cells in the bursa. The relative weight of the livers of the birds exposed to this toxin was increased and, microscopically, there was hepatocyte vacuolation and megalocytosis with accompanying hyperplasia of the biliary epithelium. The kidneys showed hypertrophy of the renal proximal tubular epithelium, with thickening of the glomerular basement membrane. Aluminosilicate did not ameliorate the deleterious effects of the ochratoxin.

Role of caspases in human renal proximal tubular epithelial cell apoptosis

In the present study, we have used an in vitro model of apoptosis using primary human renal proximal tubular epithelial (RPTE) cells to investigate the mechanisms involved in renal cell apoptosis. Treatment of RPTE cells with okadaic acid for 24–48 h induced apoptosis in a concentration-dependent manner. Apoptosis was accompanied by the activation of the p38 mitogen-activated protein kinase (MAPK) pathway followed by the activation of caspase-9, -3, and -7. The induction of caspase activity correlated with the proteolytic cleavage of β-catenin, suggesting that β-catenin is a caspase substrate. The caspase inhibitor, Z-Val-Ala-Asp-fluoromethylketone (Z-VAD-fmk), resulted in a dose-dependent inhibition of apoptosis and β-catenin cleavage. These data suggest that okadaic acid-induced apoptosis is p38 MAPK and caspase-dependent and that proteolytic cleavage of β-catenin by caspases is likely to be a downstream molecular event associated with the morphological and cytoskeletal changes induced during apoptosis.

Overexpression of heme oxygenase protects renal tubular cells against cold storage injury: studies using hemin induction and HO-1 gene transfer.

Heme oxygenase-1 (HO-1), a 32-kd microsomal enzyme, is induced as an adaptive response to a wide variety of injurious stimuli. We examined the possible role of HO-1 in cold storage of renal proximal tubular epithelial (RPTE) cells. Hemin, a potent HO-1-inducer, caused a time-dependent increase in HO-1 mRNA and protein expression. Hemin pretreatment of human RPTE cells before cold storage conferred cytoprotection. Increased HO-1 protein was associated with a brisk and early increase in catalytically active iron and a robust increase in cellular ferritin. Deferoxamine, an iron sequestrating antioxidant, prevented hemin-induced iron release and the increase in ferritin, suggesting iron release as an antecedent mechanism for ferritin induction. To verify that the proximate cause of hemin cytoprotection was due to HO-1 induction, we transiently transfected LL-CPK1 porcine kidney cells with a HO-1 expression vector before cold storage. HO-1 transfection resulted in increased expression of HO-1 protein and reduced cell injury during cold storage. The novel observation that prior induction of HO-1 prevents cold storage-induced cell injury suggests that a similar strategy may prove efficacious in preventing cold storage-induced organ damage during transplantation.

APOPTOSIS VERSUS NECROSIS DURING COLD STORAGE AND REWARMING OF HUMAN RENAL PROXIMAL TUBULAR CELLS1

A recent clinical study demonstrated that in renal allografts preserved in the cold apoptosis occurred soon after reperfusion. The mode of cell death during cold storage is generally considered necrotic. Whether apoptosis occurs as a part of cold storage is uncertain. The objective was to determine in human renal tubular cells whether apoptosis is specific for rewarming or it also occurs during cold storage and whether it could be modified. Cold storage (4 degrees C) of primary human renal proximal tubular epithelial (RPTE) in University of Wisconsin (UW) solution up to 48 hr caused a time-dependent increase in cell death measured by lactic dehydrogenase (LDH) release and vital dye exclusion methods. Transmission electron microscopy (TEM) demonstrated that cell death in the cold was necrotic, involving considerable mitochondrial disruption, and was not apoptotic. The TUNEL assay that provides a specific, quantitative measure for apoptosis showed no increase in TUNEL-positivity during flow cytometry of cells stored in cold: 37 degrees C, 0.23+/-0.14%; 24 hr cold, 0.23+/-0.1%; 48 hr cold, 1.79+/-0.58%. Annexin-V staining, a sensitive method for detecting early apoptosis, similarly showed no increase in positively stained cells during cold storage. Addition of antioxidants 2-methyl aminochroman and deferoxamine to UW solution inhibited necrotic cell death and preserved mitochondrial structure. In contrast to cold storage alone, rewarming (37 degrees C for 24 hr) of cold stored cells, however, resulted in significant apoptosis (TUNEL positive: 48 hr cold: 2+/-0.6%, 48 hr cold and 24 hr rewarming: 54+/-17%), which was confirmed by the TEM based on typical apoptotic features. Addition of 2-MAC and DFO significantly inhibited rewarming-induced apoptotic cell death (plus 2-MAC: 3+/-1%, plus DFO: 3+/-2%). Our study in human tubular cells provides evidence that cold storage per se does not result in apoptosis, but is primarily necrotic. However, rewarming is associated with significant apoptosis in the presence of ongoing necrosis, speculatively due to the activation of the apoptotic enzymic process of sublethally injured cells. Inclusion of antioxidants in the storage solution confers protection against both cold storage and rewarming-induced necrosis and apoptosis.

Defective Urinary Concentrating Ability Due to a Complete Deficiency of Aquaporin-1

Aquaporin-1, the archetypal water-channel protein,1 was initially identified in red cells and renal proximal tubular epithelium.2 The gene for aquaporin-1 (AQP1) on chromosome 7 colocalizes with the Colton blood-group antigen,3,4 and the Colton blood-group antigen polymorphism was identified as a substitution of a single amino acid in an extracellular domain of aquaporin-1.5 The International Blood Group Reference Laboratory has confirmed the existence of only six kindreds who lack the Colton blood group. Members of three of these kindreds were found to be homozygous for different mutations in the AQP1 gene, and their red-cell membranes had a complete . . .

Three-dimensional organization of the aquaporin water channel: What can structure tell us about function?

Publisher Summary The entry and exit of water across the lipid bilayer membrane is a fundamental physiological process necessary for maintaining cell homeostasis, which is crucial to the survival of an organism. The chapter discusses several observations that have been suggested in the presence of water-specific channels or pore in some tissues. These were (a) unusually high osmotic water permeability of, for instance, red blood cell membranes and renal proximal tubular epithelium, which is characterized by low Arrhenius activation energy (E a ) and is too rapid to be explained by passive diffusion of water across the bilayer, (b) reversible inhibition of the high water permeability across red blood cells by mercurial reagents, and (c) radiation inactivation studies of renal brush-border membrane vesicles and erythrocytes that indicated that a protein of ∼30kDa is responsible for the high water permeability. Additional evidence in favor of a protein responsible for water transport was provided when, upon injection of heterologous mRNAs from kidney reticulocytes and amphibian bladder into Xenopus oocytes, which is known to have low water permeability, increased water permeability was elicited.

Characterization of the Baboon Responses to Shiga-Like Toxin: Descriptive Study of a New Primate Model of Toxic Responses to Stx-1

The baboon response to intravenous infusion of Shiga toxin 1 (Stx-1) varied from acute renal failure, proteinuria, hyperkalemia, and melena with minimal perturbation of host inflammatory and hemostatic systems (high-dose group, 2.0 microg/kg; n = 5) to renal failure with hematuria, proteinuria, thrombocytopenia, schistocytosis, anemia, and melena (low-dose group, 0.05 to 0.2 microg/kg; n = 8). Both groups exhibited renal shutdown and died in 57 hours or less. Both groups produced urine that was positive for tumor necrosis factor and interleukin-6 although neither of these cytokines was detectable (</=5 ng/ml) in the general circulation. Light and electron microscopy showed organelle disintegration and necrosis of the renal proximal tubular epithelium and of the intestinal mucosal epithelium at the tips of the microvilli, both of which were previously shown to bear Gb3 receptors. The renal distal tubular epithelium was spared. The renal proximal tubular epithelial changes were accompanied by swelling of visceral epithelial cells (podocytes) and by swelling and detachment of endothelial cells of the glomerular capillaries. In addition, all of the animals receiving low-dose Stx-1 showed microvascular fibrin deposition and thrombosis in renal glomerular and peritubular capillaries in association with a fall in hematocrit and platelet count and a rise in schistocyte count. The gastrointestinal villous tip lesions were accompanied by varying degrees of mucosal and submucosal congestion, hemorrhage, or necrosis. Electron microscopic images of cerebral cortex and cerebellum showed diffuse unraveling of myelin sheaths with occasional disintegration of neuronal cell bodies. In contrast to the gastrointestinal mucosal and renal proximal tubular epithelium, the Gb3 receptor glycolipid of the renal glomerular and neuronal tissues as determined using toxin overlay thin-layer chromatography plates was below the limit of detection (<13 pM/g wet tissue). We conclude that, depending on the status of the host and amount of toxin infused, Stx-1 can produce a variety of responses ranging from damage to cells carrying the Gb3 receptor (renal proximal tubular epithelial cells and gastrointestinal mucosa) to damage to renal glomerular tissues with microvascular thrombosis as a result of the host's inflammatory response localized to the kidney. We conclude that this thrombotic coagulopathy arises from local changes in the kidney because the appearance of host inflammatory mediators was limited to the urine. This suggests that the initial host response is localized in the kidney, and that the systemic thrombocytopenia, anemia, and schistocytosis may arise secondarily.

K-Cl cotransporter expression in the human kidney.

The K-Cl cotransporter protein KCC1 is a membrane transport protein that mediates the coupled, electroneutral transport of K and Cl across plasma membranes. The precise cell type(s) in the kidney that express the K-Cl cotransporter have remained unknown. The aim of the present investigation was to define the distribution of KCC1 mRNA in the human kidney. We used in situ hybridization with a nonradioactive digoxigenin-labeled riboprobe. We identified abundant KCC1 mRNA expression in the epithelial cells throughout the distal and proximal renal tubular epithelium. The transporter was also expressed in glomerular mesangial cells and endothelial cells of the renal vessels. These findings suggest that the K-Cl cotransporter may have an important role in transepithelial K and Cl reabsorption.

The role of tissue angiotensin-converting enzyme (ACE): studies of ACE mutant mice

Angiotensin-converting enzyme (ACE) is a polypeptide chain containing 2 homologous domains, each with an independent catalytic site. The 2 sites generate angiotensin II from angiotensin I with roughly equal efficiency.1,2 Both catalytic domains are external to cells, with the ACE protein being bound to the cell membrane by a hydrophobic anchor sequence at the carboxyl terminus. The majority of somatic ACE activity is associated with such tissues as the vascular endothelium and the renal proximal tubular epithelium. A soluble form of ACE also circulates in plasma and results from cleavage of tissue-bound ACE.3 A number of findings suggest that tissue ACE has a major role in the production of angiotensin II and that it may participate in local renin–angiotensin systems that are independent of the circulating renin–angiotensin system.4 In addition to somatic ACE, a unique form of ACE, termed testis ACE, is produced by developing male germ cells. Testis ACE is approximately half the size of somatic ACE and contains one catalytic site.5 The role of testis ACE has not been fully elucidated, although it appears to be important to male fertility.6,7

Identification of a Novel Stress Activated Kinase in Kidney and Heart

We have previously described the patterns of stress kinase activation in rat kidney and heart in response to ischemia/reperfusion (Yin et al., 1997,J. Biol. Chem.272, 19943–19950). During the course of these studies, we observed the activation of a novel kinase capable of phosphorylating c-Jun on serines 63 and 73. The molecular weight of this kinase is approximately 37 kD, significantly below the molecular weight of all previously identified Jun N-terminal kinase (JNK) isoforms. The pattern of activation of this 37 kD kinase in response to ischemia/reperfusion in both kidney and heart is distinct from that of known JNK isoforms. Western analysis of human renal proximal tubular epithelial (RPTE) cells, using a non-isoform specific phospho-JNK antibody, revealed the phosphorylation (activation) of a 37 kD protein in response to hypoxia. The 37 kD protein in RPTE cells is phosphorylated by other stress stimuli capable of activating JNK. Western analysis of tissues, using a non-isoform specific JNK antibody, identifies a cross-reactive 37 kD protein expressed in the liver, thymus and lymph node which is likely to correspond to the 37 kDa stress-activated kinase. The results of this study have led to the identification of a potentially novel kinase closely related to JNK but showing a distinct pattern of activation.

Urinary neutral endopeptidase in workers exposed to cadmium: interaction with cigarette smoking.

OBJECTIVES: Structural impairment of the renal proximal tubular epithelium induced by cadmium (Cd) was investigated by measuring the concentration of neutral endopeptidase 24.11 (NEP), an ectoenzyme of the apical brush...

Cell lines with extended in vitro growth potential from human renal proximal tubule: Characterization, response to inducers, and comparison with established cell lines

Few model systems exist for the study of injury to human renal proximal tubule epithelium. Optimized differentiated human renal epithelial cell lines with extended in vitro growth potential would provide an alternative model system to primary culture or other available non-human mammalian kidney cell lines. For this purpose, human renal tubule epithelial cells were isolated from normal kidney cortex and exposed in culture to a hybrid immortalizing virus, adenovirus 12-SV40. Cell lines were developed by limiting dilution, and three selected cell lines were screened for growth pattern, production of immortalizing virus, tumorigenicity, and ploidy. Cell lines were also monitored for response to inducer agents and matrix factors and were screened for expression of biochemical properties and differentiation markers of renal epithelium. All three are nonproducers of the immortalizing virus and are nontumorigenic. They grow in monolayer, have intermediate growth kinetics, and express markers of renal proximal tubular epithelium by immunohistochemistry. They also express biochemical properties comparable to other widely used proximal tubular cell lines including LLC-RK1, OK, and HK-2 and comparable to human tubular cells in stable culture. Growth medium containing low levels of fetal calf serum, or epidermal growth factor combined with parathyroid hormone, produced optimal growth characteristics, brush border enzyme expression, biochemical properties, and glucose transport in a selected cell line. The addition of dimethyl sulfoxide allows maintenance in morphologically intact monolayers for prolonged periods. These cell lines should be useful model systems for the study of human renal proximal tubular injury or disease.

Evidence for increased synthesis of complement C4 in the renal epithelium of rats with passive Heymann nephritis.

Passive Heymann nephritis (PHN) is a complement-dependent model of immune complex glomerulonephritis. This study investigated the contribution of local complement synthesis by studying gene expression of the classical pathway component C4 in relation to the site of the tissue injury and the development of proteinuria induced by the pathogenic antibody (sheep anti-GP330). This study, using in situ hybridization, found that C4 mRNA expression was increased in the glomerular epithelium and the proximal renal tubular epithelium in a distribution similar to that of the targeted GP330 antigen. The total cortical C4 mRNA expression assessed by semiquantitative polymerase chain reaction (PCR) increased in a time-dependent manner (P < 0.05), coincident with the onset and progression of proteinuria, and peaking 11 to 14 days after the induction of the disease. These data suggest a link, in place and time, between local complement gene expression and glomerular barrier dysfunction induced by anti-GP330. It is postulated that increased epithelial synthesis of C4 stimulated by the engagement of GP330 enhances the formation of the membrane attack complex of complement through its classical pathway, and, hence, the formation of complement-mediated injury.

Immunohistochemical detection of P-glycoprotein in formalin-fixed and paraffin-embedded normal and neoplastic canine tissues.

Expression of P-glycoprotein, a phylogenetically conserved integral plasma membrane protein, is implicated as one of the most important factors contributing to tumor cell multidrug resistance. Formalin-fixed, paraffin-embedded normal and neoplastic canine tissues were studied using an avidin-biotin complex technique employing three murine monoclonal antibodies (C494, C219, JSB-1) to different epitopes of the P-glycoprotein molecule. Evaluation of immunostaining of normal canine tissues revealed positive labeling detected by each antibody in the liver, proximal renal tubular epithelium, adrenal cortex, colonic epithelium, and capillary endothelial cells of the brain. A total of 166 tumors of epithelial or mesenchymal origin were evaluated for P-glycoprotein immunoreactivity. Hepatomas (4/4), colorectal adenomas (7/7), colorectal carcinomas (4/4), adrenal cortical adenomas (3/3), hemangiopericytomas (15/15), apocrine gland adenocarcinomas (4/5, 80%), and transitional cell carcinomas (2/2) consistently labeled with at least one of the antibodies. Histiocytomas (0/10), cutaneous plasma cell tumors (0/10), fibromas (0/3), fibrosarcomas (0/4), and leiomyomas (0/4) were uniformly negative with all antibodies. Malignant lymphomas (6/22, 27.3%), malignant melanomas (4/13, 30.8%), leiomyosarcomas (3/6, 50%), mammary gland carcinomas (12/19, 63.2%), mammary gland adenomas (3/9, 33.3%), squamous cell carcinomas (8/10, 80%), basal cell tumors (5/7, 71.4%), apocrine gland adenomas (1/2, 50%), cholangiocarcinomas (2/3, 66.7%), and thyroid gland carcinomas (2/4, 50%) gave variable results. The antibodies C494, JSB-1, and C219 labeled 66/166 (39.8%), 53/166 (31.9%), and 38/166 (22.9%) of all tumors studied, respectively. A total of 26/166 (15.7%), 22/166 (13.3%), and 37/166 (22.6%) of tumors were labeled by all three, just two, or one antibody alone, respectively. The antibody C494 was the only antibody labeling 28/166 (16.9%) of the cases. JSB-1 alone labeled 9/166 (5.4%) of the tumors. C219 failed to label any tumors not also labeled by either C494 or JSB-1. Labeling by C494 was more intense and specific than labeling by the other two antibodies. Results indicate that P-glycoprotein can be detected in routinely processed canine tissues. The detection of P-glycoprotein within canine liver, kidney, adrenal gland, and colon and within tumors arising from these tissues is consistent with that reported in the literature for human tissues. Variable labeling results of other tumors such as malignant lymphoma and mammary gland carcinomas also is consistent with reports of human studies. Detection of multidrug resistance markers such as P-glycoprotein in canine tissues may provide additional information upon which to base a prognosis or to design treatment regimens for canine tumors.

Regulated expression of complement factor B in the human kidney

We have previously demonstrated regulated expression of C3 in the proximal renal tubular epithelial cells of humans. To test the hypothesis that local alternative pathway complement activation could contribute to the tubulointerstitial component of chronic renal disease, we examined factor B gene expression in human kidneys. 35S riboprobes were generated from a human factor B cDNA. By in situ hybridization, proximal tubular factor B message was seen in 17 kidneys with various nephropathies. The expression was most intense in organs with evidence of interstitial inflammation, and its localization paralleled the inflammation. As was the case with C3 and C4, there was never any evidence of glomerular factor B message, nor was any seen in infiltrating inflammatory cells. In eight normal kidney tissues, factor B expression was either absent or restricted to rare foci of interstitial infiltration. The proximal renal tubular epithelium of humans appears to express the genes for both components of the alternative pathway convertase, C3 and factor B. These locally produced components may be important mediators of the interstitial inflammation that is common to all progressive nephritides.

Renal proximal tubular epithelium from patients with nephropathic cystinosis: Immortalized cell lines asin vitro model systems

Renal proximal tubular epithelium from patients with nephropathic cystinosis: Immortalized cell lines asin vitro model systems

Gene regulation of senescence marker protein-30 (SMP30): coordinated up-regulation with tissue maturation and gradual down-regulation with aging

Senescence marker protein-30 (SMP30) is a calcium binding protein also called regucalcin. The amounts of SMP30 decrease androgen-independently with aging in the livers of rats. We have studied the expression of SMP30 in livers and kidneys of rats from the embryonic to the senescent stages of life. No transcript was detected in livers or kidneys in day 18 embryos. However, Northern blot analysis showed a marked increase of SMP30 mRNA in livers of neonatal and young rats. The first peak of SMP30 transcript was found in a 5-day-old neonate, in which the amount of mRNA was threefold higher in comparison with 3- to 6.5-month-old adults. The expression of SMP30 protein started to increase from day 7 and rapidly reached a plateau at day 10. The substantial amounts of protein and transcript were maintained in adults up to 3–6.5 months of age. In the kidney, SMP30 mRNA and protein started to increase at day 21 and reached near-maximal levels at day 35. The levels of transcript and protein remained high in adults up to 3 months of age. As the aging process progressed to senescent stages, the levels of transcript and protein decreased significantly in the liver and kidney of aged rats. Therefore, the age-associated decrease of SMP30 in the liver and kidney may be, in a large part, controlled at transcriptional levels. Furthermore, immunohistochemical analysis showed a similar pattern of changes in SMP30 protein expression during neonate, adult and senescent stages in hepatocytes and renal proximal tubular epithelia. The high expression of SMP30 in the tissue-maturing process and adult-hood suggests that SMP30 may be required for the maintenance of highly differentiated hepatic and renal functions.

The uptake and effects of lead in small mammals and frogs at a trap and skeet range.

This study was performed to evaluate the bioavailability and effects of lead in wildlife at a trap and skeet range. The total lead concentration in a composite soil sample (pellets removed) was 75,000 micrograms/g dry weight. Elevated tissue lead concentrations and depressed ALAD activities in small mammals and frogs indicate that some of the lead deposited at the site is bioavailable. Mean tissue lead concentrations (micrograms/g dry wt.) in white-footed mice (Peromyscus leucopus) at the range liver = 4.98, kidney = 34.9, femur = 245) were elevated (P < 0.01) 5- to 64-fold relative to concentrations in mice from a control area. Tissue lead concentrations in the only shorttail shrew (Blarina brevicauda) captured at the range (liver = 34.1, kidney = 1506, femur = 437) were elevated 35- to 1038-fold. Femur lead concentrations in green frogs (Rana clamitans) at the range (1,728 micrograms/g) were elevated nearly 1000-fold, and the lead concentration in a pooled kidney sample (96.2 micrograms/g) was elevated 67-fold. There was significant depression of blood ALAD activity in mice (P = 0.0384) and depression of blood and liver ALAD activity in frogs (P < 0.001). Hematological and histopathological lesions associated with lead toxicosis were observed in some animals. Hemoglobin concentrations were reduced 6.7% in mice (P = 0.0249), but hematocrit was not significantly affected in mice or frogs. Intranuclear inclusions were present in the renal proximal tubular epithelium of two of the mice and the shrew that were captured at the range, and necrosis of the tubular epithelium was also evident in one of the mice. Kidney:body weight ratios were similar in range and control mice. Soil ingestion may be a significant route of lead uptake in small mammals at the range. However, the tendency of lead to concentrate in the bones rather than in more digestible soft tissues may minimize food chain uptake of lead by predators, especially raptors that regurgitate undigestible material.