Renal Proximal Tubular Epithelium Research Articles

Tissue Non-Specific Alkaline Phosphatase May Be a Function-Related Marker in Renal Proximal Tubular Epithelia and in Vascular Endothelia as It Is in Osteoblasts

Tissue non-specific alkaline phosphatase (TN-AP) is a multifunctional phosphatase and has a variety of substrates in vitro. In adults, TN-AP is highly expressed in osteoblasts, renal proximal tubular epithelia and vascular endothelia. In osteoblasts, it is well known that TN-AP plays an important role in bone mineralization. Considering its many activities in vitro, we hypothesize that TN-AP also plays a role in regulating cellular activities in renal proximal tubular epithelia and vascular endothelia. By using a stable gene transfection technique, we transfected two cell lines with a rat TN-AP gene, one renal proximal tubule-like (LLC-PK1), another vascular endothelia-like (Py-4-1). The effect of TN-AP expression was cell specific. In Py-4-1 cells, the forced TN-AP expression stimulates cellular behaviours associated with terminal differentiation. This suggests that in vivo AP expression in certain vascular endothelia may mark a terminal-differentiated subpopulation with less angiogenic potential. While, in LLC-PK1 cells, the forced TN-AP expression inhibited cellular transport function as demonstrated by delayed dome formation. By inference, TN-AP expression in renal proximal tubule in vivo should have a regulatory role in cellular transport. Our data suggest that TN-APs have roles as function-related markers in renal proximal tubular epithelia and vascular endothelia.

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

The renal proximal tubule is a major site of injury in a variety of congenital/metabolic diseases including nephropathic cystinosis, the most commonly known cause of renal Fanconi's syndrome. In this lysosomal storage disease there are defects in proximal tubule function within the first few months of life. While culture of renal tubular cells from the urine of these patients is possible, development of immortalized cell lines would insure large numbers of homogeneous cells for studies of renal epithelial cell morphology and pathophysiology in this disease. To develop immortalized cells, cystinotic and normal proximal tubular cells in culture were exposed to an immortalizing vector, containing pZiptsU19 with the temperature sensitive SV40 T-antigen allele tsA58U19 and a neomycin resistance gene, and neomycin-resistant tubular cells were selected for propagation. Ten clones from cystinotic patients have been developed and characterized. All clones express T-antigen at permissive temperature (33 degrees C). Immortalized cells have an epithelial morphology and grow to form confluent monolayers; doubling times vary from 31 to 86 hours. Cystinotic clones are keratin, MDR P-glycoprotein, and alpha-95 kD brush-border associated protein positive but Tamm-Horsfall protein negative by immunocytochemistry, as are normal proximal tubule cells immortalized with this vector. This is consistent with a proximal tubule origin of the cystinotic clones. The cystine content of the cystinotic cells is 70 to 160 times that of normal renal proximal tubular cells in culture, with most of the cystine sequestered in cell lysosomes, confirming that these cell lines express the storage defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Sensitivity of selected immunological, hematological, and reproductive parameters in the cotton rat (Sigmodon hispidus) to subchronic lead exposure.

The effect of lead exposure on cellular immunity, hematology, and reproductive and body condition in mature cotton rats (Sigmodon hispidus) was examined. Two groups of 36 cotton rats each were exposed to 0, 100, or 1,000 ppm lead in drinking water for either 7 or 13 weeks, between 31 August and 2 December 1990. Specific and non-specific cell-mediated immunity was assessed by measuring splenocyte proliferative responses to polyclonal mitogens (Concanavalin A and Pokeweed mitogen), in vivo 24-hr delayed-type hypersensitivity, metabolic activity of peritoneal macrophages, spleen mass and cellularity, and immune organ development. General physiological condition was assessed from hematological, morphological, and reproductive measures. Immune function was sensitive to lead exposure based on depressed proliferative responses of cultured splenocytes, smaller popliteal lymph nodes, and larger spleens among cotton rats receiving 1,000 ppm lead. Spleen mass was reduced in cotton rats receiving 100 ppm lead. Total leukocytes, lymphocytes, neutrophils, eosinophils, total splenocyte yield, packed cell volume, hemoglobin, and mean corpuscular hemoglobin were sensitive to lead exposure. Effects of lead exposure on general condition and reproductive parameters included reduced mass of liver, seminal vesicles, and epididymes in males following a 7-week exposure. Histopathologic changes reflected lead toxicity and included altered renal proximal tubular epithelium, renal intranuclear inclusions, and in some cases, lowered numbers of sperm and developing follicles. In general, lesions were more pronounced with increased lead concentration and longer exposure.

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.

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.

Isolation of cDNA clone encoding rat senescence marker protein-30 (SMP30) and its tissue distribution

We have isolated and characterized two cDNA clones encoding senescence marker protein-30 (SMP30), the amounts of which are known to decrease androgen-independently with aging in the livers of rats. Of these cDNA clones, one consisted of 1588 bp nucleotides and the other of 1195 bp nucleotides generated by alternative polyadenylation. These two cDNA clones shared the same open reading frame, but the larger species had 393 bp nucleotides of 3′ untranslated region in addition to the first polyadenylation site of smaller species. Northern hybridization analysis showed that two species of mRNA (1.7 kb and 1.4 kb) located in the liver and kidney were consistent with these short and long forms of cDNA. The open reading frame, 897 bp could encode 299 amino acids. The estimated molecular weight and p I of the deduced polypeptide were 33 387 and 5.1, respectively. Furthermore, immunohistochemical analysis confirmed that SMP30 was preferentially localized in the hepatocytes and renal proximal tubular epithelium. Genomic Southern hybridization analysis demonstrated that SMP30 was widely conserved among higher animals. A computer-assisted homology analysis of nucleic acid and protein databases revealed no remarkable homology with other known proteins. Therefore, SMP30 seems to be a novel protein. In addition, the existence of putative A-U rich mRNA degradation signals and protein degradation signals (PEST sequence) in the structure of SMP30 may suggest important regulatory function of this unique protein manifested by changes in its concentrations.

Organic cation transport by cultured renal proximal tubular epithelia

Described are the methods used to study the transport of organic cations across the apical membrane of LLC-PK1 and OK cells. The method for performing a time course experiment of tetraethylammonium uptake is also outlined.

Ioxaglate-Induced Light and Electron Microscopic Alterations in the Renal Proximal Tubular Epithelium of Rats

Vacuolization of the proximal tubular epithelial cells was produced in rats by the intravenous administration of the radiographic contrast medium ioxaglate at high multiples of the human diagnostic dose. Samples of the renal cortex and outer zone of the medulla were examined by light and electron microscopy. We observed enlargement, confluence, and migration of vacuoles containing pleomorphic dense material and distinct inclusion bodies. With time, vacuolization disappeared, though single vacuoles partly engaged in extruding their contents into the tubular lumen were still visible. We concluded that radiographic contrast medium at high dose levels can produce a reversible disturbance in the transport vesicular system of the proximal tubular epithelial cells without affecting the specific cell organelles.

Fifty-two-weeks oral chronic toxicity study of propiverine hydrochloride in rats.

An oral chronic toxicity study of propiverine hydrochloride (P-4), a new anti-pollakiuria agent, was carried out at dose levels of 0 (control), 0.5, 5 and 50 mg/kg/day using male and female rats. They were treated for 52 weeks, followed by 5 weeks recovery period. The results obtained from the present study were as follows. 1. There were no deaths related to P-4. Mydriasis, transitory salivation were observed in both sexes receiving 50 mg/kg/day, and soil of the abdomen was also noted in females receiving 50 mg/kg/day. 2. Body weight gain was suppressed from initiation of administration in both sexes receiving 50 mg/kg/day. 3. There were no significant or remarkable changes in food consumption, hematology and ophthalmology. 4. Urinary findings in animals receiving 50 mg/kg/day showed increases of urine and potassium excretion volumes and decrease of urine osmotic pressure in both sexes, negativity of urine protein and decrease of urobilinogen value in females. 5. Biochemical findings in animals receiving 50 mg/kg/day showed increase of urea-nitrogen (Urea N) in both sexes and decrease of triglyceride (TG), total cholesterol (T. cho), free cholesterol (F. cho), non-esterified fatty acids (NEFA) and phospholipid (PL) in males. 6. The absolute and/or relative weights of the liver increased in animals receiving 50 mg/kg/day. Histopathological examination in animals receiving 50 mg/kg/day revealed intranuclear eosinophilic inclusions and cytoplasmic eosinophilic substance in renal proximal tubular epithelium and midzonal lipid droplets in liver. Histochemical examination in animals receiving 50 mg/kg/day revealed the slight increase of gamma-GTP positive area in peripheral zone of liver. Electron-microscopic examination in animals receiving 50 mg/kg/day revealed intranuclear and intracellular large and homogeneous spherical-like structure with low electron density in renal proximal tubular epithelium, and slight hyperplasia of smooth endoplasmic reticulum with dilatation of cisternae and deposition of large lipid droplets in hepatocytes, but there was no difference of VLDL and its distributions in hepatocytes among groups.(ABSTRACT TRUNCATED AT 400 WORDS)

Carbohydrate metabolism by primary cultures of rabbit proximal tubules

Renal proximal tubular epithelia were used to assess the factors responsible for the induction of glycolysis in cultured cells. Primary cultures of rabbit proximal tubules, which achieved confluency at 6 days, exhibited hormonal responsiveness and brush-border characteristics typical of proximal tubular cells. Beginning at day 4, these cultured cells exhibited increased glycolytic metabolism reflected by enhanced glucose uptake and lactate production, along with parallel increases in activity of the glycolytic enzymes, pyruvate kinase and lactate dehydrogenase. The gluconeogenic enzymes, phosphoenolpyruvate carboxykinase (PEPCK) and fructose-1,6-bisphosphatase (FDP), were downregulated, and the cultured cells exhibited lower oxygen consumption rates than fresh tubules. Cells grown on a rocker, to mitigate hypoxia, exhibited a metabolic and enzymatic profile similar to cells grown under still conditions. ATP levels in cultured cells were higher than in fresh tubules. Furthermore, pyruvate kinase activity was higher in cells grown in media containing 0.5 as contrasted with 25 mM glucose. The enhanced glycolytic metabolism exhibited by cultured proximal tubular cells appears to be a characteristic of proliferation and is not a response to hypoxia, the Pasteur effect, or environmental glucose.

Electrophysiologic study of rabbit proximal tubular cell monolayers in primary culture.

Primary cultures of renal cortical cells prepared by selective sieves have been found to display some characteristics of renal proximal tubular epithelium but their site of origin has not been confirmed by electrophysiologic studies. Cells were cultured in a defined medium on collagen gels. Confluency was approached after 7-10 days but gels were found to have zero transepithelial resistance unless they were allowed to contract spontaneously. With the appearance of a nonzero resistance, there was a change in morphology to a more columnar cell with better developed microvilli. These structural features were particularly prominent in clusters of proliferating cells observed on and around remnants of original tubules embedded in the gel. In noncontracted cultures there was no focal cell clustering and cells were squamous-like with rudimentary microvilli, similar in appearance to cells grown on plastic culture dishes. Measurements made in contracted monolayers yielded an average transepithelial resistance of 6.5 omega cm2, a spontaneous transepithelial potential difference of +0.9 mV, measured with respect to the serosa, and an apical membrane potential of -75 mV when cells were bathed in 0.4 mM K and -49 mV when cells were bathed in 4 mM K media. Mucosal protamine (50 micrograms/ml) increased transepithelial resistance by 22%, suggesting that the epithelial cell tight junctions were responsive to external stimuli. Monolayers were anion selective, giving a dilution potential (lumen-directed NaCl gradient) of -2.6 mV with respect to the serosa. These experiments show that primary culture of rabbit renal cortical cells separated by differential sieves displays electrophysiologic and morphologic characteristics of a proximal renal tubular epithelium. Confluency and attainment of differentiated morphology and function are promoted when monolayer cells are not bound to an unyielding substrate.

The Na+/H+ antiport, cytosolic free Ca2+, and essential hypertension: a hypothesis.

We propose that in essential hypertension higher cytosolic free Ca2+ ([Ca2+]i) is associated with hyperactivity of the Na+/H+ antiport and that augmented activity of this transport system explains at least some abnormalities in Na+ metabolism associated with this disease. In low-renin essential hypertension, a higher [Ca2+]i is present not only in vascular smooth muscle cells of resistance vessels but also in juxtaglomerular cells and renal proximal tubular epithelium. A higher [Ca2+]i in juxtaglomerular cells retards renin secretion, whereas in renal proximal tubules it is associated with increased Na+ reabsorption via the Na+/H+ antiport. Thus, hyperactivity of the Na+/H+ antiport in renal tubular epithelium may be the cause of salt (NaCl) sensitivity. Ca2+ antagonists probably exert their antihypertensive effect by reducing [Ca2+]i in both vascular smooth muscle cells and renal tubular epithelium. These agents are, therefore, particularly effective in the treatment of essential hypertension in blacks and older individuals with the low-renin form of the disease, who are known to be salt sensitive.

Characterization of cytoplasmic lysozyme immunoreactivity as a histiocytic marker in normal canine tissues.

The immunoreactive lysozyme distribution in normal canine tissues was determined to assess the value of lysozyme as a marker of histiocytic differentiation. Lysozyme was largely confined to monocytes, neutrophils, macrophages, serous cells in mucosal associated exocrine glands, and renal proximal tubular epithelium. Macrophages in the majority of tissues stained intensely for lysozyme, although in lymphoid tissues not all acid phosphatase and nonspecific esterase positive cells contained lysozyme. In particular, dendritic antigen presenting cells, including Langerhans cells, follicular dendritic cells, and interdigitating reticulum cells, lacked immunoreactive lysozyme; hence lysozyme appeared to represent a discriminatory marker with respect to these cells. Also, a small proportion of non-dendritic macrophages appeared to lack lysozyme. It was concluded that the demonstration of immunoreactive lysozyme was a useful adjunct to conventional morphological techniques for the identification of tissue macrophages provided that due caution was exercised in the interpretation of the results of lysozyme staining.

γ-Glutamyl Transpeptidase Excretion in Cisplatin-Induced Acute Renal Failure

Cisplatin (cisdiamminedichloroplatinum), an important antineoplastic agent, possesses nephrotoxicity as its major side effect. A mild partially reversible nonoliguric form of acute renal failure (ARF) is generally the most common form of nephrotoxicity and occurs in experimental animals following a single dose. gamma-Glutamyl transpeptidase (gamma GT) is an enzyme with maximal activity located in the brush border of proximal renal tubular epithelium. To test the relationship between cisplatin nephrotoxicity and urinary gamma GT excretion, rats received a single 5.5 mg/kg dose of cisplatin and gamma GT excretion was evaluated and compared to anatomic and functional damage. Twenty-four hours following cisplatin administration, there was a marked enhancement of urinary gamma GT excretion, prior to the onset of azotemia. Urinary gamma GT excretion peaked at day 4, then returned to baseline, and decreased to values below baseline on days 8 through 10. By days 11 through 12, renal function and urinary gamma GT excretion had returned to normal. The correlation between nephrotoxicity, changes in urinary gamma GT excretion, and anatomic damage was excellent. Morphologically, increased gamma GT excretion was associated with loss of microvilli, and the return of urinary gamma GT excretion to normal correlated with their regeneration. We conclude that cisplatin administration results in increased urinary gamma GT excretion. This early enhancement, prior to the onset of azotemia, may provide a useful noninvasive marker of early cisplatin nephrotoxicity.

Light- and electron-microscopic evaluation of renal tubular cell vacuolation induced by administration of nitrilotriacetate or sucrose

Cytoplasmic vacuolation of renal proximal tubular epithelial cells was studied in rats following administration of nitrilotriacetate (NTA) or sucrose. Sucrose was administered at both a high dose (29.2 mmol/kg) and low dose (7.3 mmol/kg) by ip injection. Both levels of sucrose induced severe vacuolation of the renal proximal tubular epithelium, as observed by light microscopy. However, at the high dose, the vacuolation was widespread, affecting essentially all the proximal tubules, while at the low dose, the lesion was distributed in a multifocal pattern. Nitrilotriacetate administered by gavage at a level of 7.3 mmol/kg also induced severe cytoplasmic vacuolation in the renal proximal tubular epithelium. The distribution of this lesion was multifocal and indistinguishable from that caused by the 7.3-mmol/kg dose of sucrose. Electron-microscopic examination of vacuolated tubule cells demonstrated that, in both the NTA- and sucrose-treated animals, the lesion was due to changes in the endocytotic/lysosomal system. The nuclei, mitochondria, golgi and endoplasmic reticulum and the highly convoluted areas of the basal membrane appeared normal in both the vacuolated and non-vacuolated tubule cells of rats given either NTA or sucrose.

Comparative nephrotoxicity of hydroxygentamicin and other aminoglycosides in rats

The nephrotoxicity of hydroxygentamicin and amikacin was examined in young adult Fischer 344 rats. Serum creatinine (SCr) and urea nitrogen (BUN) levels were not significantly affected following sc injection of 80 or 160 mg/kg/day of hydroxygentamicin for 15 days. However, 250 mg/kg of amikacin produced significant increases in both parameters and in kidney/body weight ratios. The ratios were also significantly increased after 80 or 160 mg/kg of hydroxygentamicin, but kidneys of rats receiving amikacin were considerably heavier than those of rats treated with hydroxygentamicin. The antibacterial potency of 250 mg/kg of amikacin is comparable to that of 100mg/kg of hydroxygentamicin. Additional studies, directly comparing hydroxygentamicin, a mutational biosynthetic, with gentamicin or netilmicin, all at 40, 80, and 160 mg base/kg, and incorporating renal function parameters as well as SCr, BUN, organ weight, tissue concentration, and kidney histopathology, revealed a characteristic pattern typical of aminoglycoside nephrotoxicity in mature adult male rats. In most parameters, values in rats given hydroxygentamicin or netilmicin were normal and comparable to those in controls, but kidney/body weight ratios were significantly increased at high doses. However, kidneys of rats medicated with gentamicin at comparable doses were considerably heavier than those of hydroxygentamicin-treated rats. Significant nephrotoxicity also was seen in rats given low doses of gentamicin or netilmicin. Eosinophilic granulation and vacuolization of renal proximal tubular epithelium, interstitial inflammation, and tubular dilation were observed microscopically with all three drugs in the following descending order of severity: gentamicin > netilmicin > hydroxygentamicin. The effects on proximal tubular epithelial cells following treatment with amikacin, netilmicin, or hydroxygentamicin correlated reasonably well with renal drug concentrations, but drug concentrations of gentamicin, which produced the most extensive kidney injury, were lower than those of the other three aminoglycosides. Elevated SCr or BUN were indicative of the presence of nephrosis, but early stages of tubular epithelial degeneration were not predicted by increases in BUN or SCr. Although minimal or mild nephrosis was seldom predicted by polyuria, proteinuria, or changes in osmolality, effects observed in renal function parameters usually correlated well with renal histopathology. However, a decrease in osmolality correlated best with enlarged kidneys and changes in renal morphology.

Chronic toxicity of methylmercury chloride in rats: pathological study.

Four groups of 56 Sprague-Dawley SPF rats of both sexes were maintained on diets containing 0, 0.4, 2 or 10 ppm methylmercury chloride (MMC) for 130 weeks to examine the pathological changes in the chronic toxicity of this compound. Sixteen males and 12 females of the 10 ppm group were affected by the toxic peripheral sensory neuropathy characterized by loss of nerve cells in the spinal ganglion and nerve fiber degeneration in the spinal dorsal root, spinal dorsal funiculus and distal peripheral nerve. There were no histological changes in the cerebrum and cerebellum from the animals of any treated groups. Toxic changes in the renal proximal tubular epithelium were observed in the 2 and 10 ppm groups of either sex. Such changes were more prominent in the 10 ppm group, and were followed by subsequent interstitial fibrosis after 64 weeks. The animals with these severe renal lesions frequently showed hyperparathyroidism. In addition, there were significantly increased incidences of hepatic bile duct hyperplasia, splenic hemosiderosis and extramedullary hematopoiesis in males, and polyarteritis nodosa in females of the 10 ppm group. The tumor incidence was not altered by the feeding of MMC.

Co- and counter-transport mechanisms in brush border membranes and basal-lateral membranes of intestine and kidney.

One way to obtain a deeper understanding of the complex function of the small intestinal and renal proximal tubular epithelium is to dissect it into single components and then, having defined the components under well-controlled conditions, try to describe the behaviour of the whole system on the basis of the properties of the single components. Brush border and basal-lateral membranes can be isolated by different methods, including free flow electrophoresis, differential and gradient centrifugation. Transport can be analysed in vesiculated membrane fractions by tracer techniques and spectrophotometric techniques. Different sodium-solute co-transport mechanisms were identified in the brush border membrane. Until now, studies with vesicles failed to document a sodium-chloride co-transport mechanism satisfactorily. On the other hand, a sodium/proton and a chloride/hydroxyl exchange mechanism were documented. These two exchange mechanisms could represent partial reactions of the postulated electroneutral sodium-chloride co-transport. In addition to different sodium-independent transport systems, the basal-lateral membrane contains an ATP-driven transport system for calcium as well as a sodium/calcium exchange mechanism. Studies with membrane vesicles isolated from animals which have been exposed to different dietary conditions or in which the parathyroid hormone or 1.25(OH)2VitD3 level has been altered show altered transport of calcium and inorganic phosphate. Thereby, it might be possible to identify the biochemical mechanisms involved in transport regulation.

Acute toxicity of 1,2-dibromo-3-chloropropane in the F344 male rat: I. Dose-response relationships and differences in routes of exposure

Single treatments of F344 male rats with the nematocide 1,2-dibromo-3-chloropropane (DBCP) produced acute injury to the kindney, epididymis, testis, and liver. Severity was proportional to the size of the dose administered, but the kidney was adversely affected at a lowere single dose (40 mg/kg) than was the testis or liver (80 mg/kg). Primary target cells in the kidney were proximal tubular epithelia in the outer medulla. Disturbances in renal function included impaired tubular reabsorption (e.g., glucose, fluid, and electrolyte transport) and reduced glomerular filtration. Mild, hepatocellular swelling was produced by 40 mg/kg DBCP, while the leakage of intracellular enzymes into the blood, and centrolobular hepatocellular necrosis occurred after 80 and 120 mg/kg, respectively. The acute testicular lesion was characterized by degeneration and desquamation of the caput epididymal (head of the epididymis) epithelium and by disruption of the seminiferous tubular architecture; these effects were more severe after 120 mg/kg than after 80 mg/kg. Comparisons of the acute toxicity of DBCP following repeated sc, po (by gavage), and ip administration (40 mg/kg daily for 4 days) failed to reveal qualitative differences attributable to the route of exposure. However, the severity of the renal lesion appeared comparatively greatest when treatment occurred sc. These results indicate that DBCP is a cytotoxicant for epididymal and renal proximal tubular epithelia and, since lesions were produced by repeated exposure to acutely subtoxic doses, suggest that its effects on these tissues may be cumulative.

Brindled mottled mouse: morphological changes of brain and visceral organs in hemizygous males following copper supplementation.

Intraperitoneal injections of cupric chloride prevent neuronal degeneration in the hemizygous brindled mottle mouse, MO br/Y, a murine model of kinky hair syndrome (KHS) in humans. At 6-9 months after two i.p. injections, the brain of MO br/Y revealed slightly increased amounts of lipofuscin pigments in the cerebral cortical neurons, cytoplasmic inclusions in the thalamic neurons, and axonal spheroid formation in the tuber cinereum, cerebellum and brain stem. Increased numbers of mitoses, bizarre hyperchromatic giant nuclei, and numerous clear vacuoles were frequently seen in the proximal renal tubular epithelium. Numerous myelin figures were conspicuous features in these epithelial cells at ultrastructural level. Such changes were not found in the littermate controls but in the heterozygous brindled mottled mouse, MO br/ +, identical changes were noted in equal or even higher frequency. These observations suggest that cupric chloride injections effectively modify the expression of the genetic defect in MO br/ Y.