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H Endou

Publications and source records attributed to H Endou.

At least 109 records · Page 6Linked to original sources
PubMed1995

Evidence suggesting a role for phospholipase C isozyme, PLC-delta 1 in corticomedullary osmotic gradients in rat kidneys.

We determined the distributional patterns of phospholipase C isozymes within the rat kidneys. PLC-beta1 was localized in the inner medulla at the highest degree followed by the inner stripe of the outer medulla, the cortex and the outer stripe of the outer medulla. PLC-gamma1 was distributed homogeneously along the corticomedullary axis. PLC-delta1 showed gradual increase from the cortex to the inner medulla. Tissue osmotic gradients were measured using 4 slices, resulting in gradual increase from the cortex to the inner medulla. The pattern of PLC-delta1 appeared very similar to the osmotic gradient in the kidney. The results suggest that the distinct patterns of the PLC isozymes may be associated with different signal transduction pathways along the corticomedullary axis and PLC-delta1 may play a role in the osmoregulation of the medullary region.

Animals↗
PubMed1994

[Micromethods for the determination of metabolic characteristics in individual nephron segments].

Since a single nephron is a functional unit of the kidney, individual microdissected segments from the nephron would be ideal tissue samples for investigations on renal pharmacology. Several micromethods have enabled researchers to analyze the biochemical and pharmacological characteristics of these nephron segments. Miniaturized cuvettes containing microliter volumes of samples can be applied for general procedures of photometry like Lowry's protein determination. Fluorometry becomes a more sensitive method when enzymatic cycling systems of NAD/NADH or NADP/NADPH are combined, which have been used for assays of enzyme activities or substrate contents in minute biological samples having tissue proteins less than 1 microgram. The microchemiluminescence procedure has been successfully utilized for cellular ATP content or oxygen radical generation. Radioimmunoassay can be used to determine endogenous components such as cyclic nucleotides, eicosanoids, etc. Continuous gradient polyacrylamide microgels prepared in 5- to 10-microliters capillaries have made it possible to quantify the intranephron distribution of cytochrome P-450, xanthine oxidase and superoxide dismutase. As an example of the modern techniques, microscopic fluorometry using Fura-2AM has been established to identify agonist-induced cytosolic free calcium transients.

Ammonia↗
PubMed1994

Renal gluconeogenesis in man: comparison with rats and rabbits.

To provide evidence on renal gluconeogenesis in humans and to compare with rats and rabbits, glucose production from several substrates was determined using cortical slices of the three species. In humans, the normal parts of kidney tissue were obtained from six cases of transitional cell carcinoma of the renal pelvis and four cases of renal cell carcinoma. Renal cortical slices were incubated aerobically with or without substrates, and the glucose contents were assayed photometrically. The specificity of human kidneys was evaluated by comparison with the results obtained from rats and rabbits. The rank order of renal gluconeogenesis from various substrates was as follows: Humans: pyruvate > oxaloacetic acid > lactic acid > fructose-1,6-diphosphate > L-glutamine. Rats: pyruvate > fructose-1,6-diphosphate > oxaloacetic acid > lactic acid > L-glutamine. Rabbits: fructose-1,6-diphosphate > pyruvate > oxaloacetic acid > lactic acid >> L-glutamine = 0. In general, the human kidney can produce glucose at the lowest rate among the three species. The substrate specificity of humans was more or less similar to that of rats. These results suggest the existence of a species difference in renal gluconeogenesis both in substrate specificities and quantitative activities.

Aged↗
PubMed1994

Intranephron distribution of creatine content in rats.

Creatine is a high energy phosphate donor and play an important role not only in muscle contraction, but also in buffering intracellular energy storage. In this study, we have identified the creatine content in microdissected nephron segments with an ultramicromethod. All nephron segments tested contained creatine, however the distribution was not uniform. Glomerulus, cortical thick ascending limb of Henle's loop and distal tubule possessed comparatively large amounts of creatine when calculated as pM/micrograms tissue protein. When calculation was made as pM/mm tubule length, the first segment of the proximal tubule and the distal tubule were the highest. These results suggest the existence of heterogeneity in creatine content along the nephron as one of the biochemical characteristics in individual nephron segments.

Analysis of Variance↗
PubMed1993

Localization of hepatitis C viral RNA and capsid protein in human liver.

In the livers of patients whose sera contained antibodies to C100-3 antigen (anti-HCV) and hepatitis C virus (HCV) RNA, the presence of HCV RNA and HCV capsid protein (CP) antigen was demonstrated by in situ hybridization and immunohistochemistry, respectively. It was found that occasional hepatocytes in four of ten livers from patients whose sera were positive for both anti-HCV and HCV RNA hybridized with antisense as well as sense oligonucleotide DNA probes, whereas the probes did not hybridize with livers from patients whose sera were negative for anti-HCV and HCV RNA. Monoclonal antibody against a synthetic oligopeptide with amino acid sequence of HCV CP reacted with occasional hepatocytes in six of 14 livers from patients whose sera contained these HCV markers, but not with livers from patients whose sera were negative for both of them. These results suggest that HCV proliferates within hepatocytes since both antisense and sense probes hybridized with cytoplasm of the hepatocytes and that the virus matures in the cytoplasm as the capsid proteins were also found in the hepatocytes.

Adult↗
PubMed1992

Cisplatin-induced alterations in renal structure, ammoniagenesis and gluconeogenesis of rats.

Cisplatin [cis-diamminedichloroplatinum (II): CDDP] is a widely used cancer chemotherapeutic agent which has been shown to cause dose-related acute renal failure. The kidney damage is histologically characterized by widespread tubular necrosis, predominantly found in the third segments (S3) of the proximal tubules. To identify the intranephron targets of CDDP more precisely, we examined alterations in ammoniagenesis (AMG) and gluconeogenesis (GLG) using rat kidney slices (for AMG and GLG), tubule suspensions (for GLG), and microdissected nephron segments (for AMG). Ultramicroassay of AMG was carried out using the enzymatic cycling method, and GLG was measured by the HK/G6PHD method. GLG obtained from kidney slices and tubule suspensions on day 3 and day 7 following CDDP treatment did not change significantly from levels in control rats. In contrast, AMG increased on day 3 in the first and third kidney slices cut from the surface inward and decreased significantly on day 7 in the third and fourth slices. Microdissected nephron segments examined on day 7 showed decreased AMG in the second segments (S2; 20.3 +/- 7.7 pmol/mm/15 min vs. 78.7 +/- 9.7 for control, P less than 0.005) and the third segments (S3; 26.3 +/- 14.4 pmol/mm/15 min vs. 79.2 +/- 7.8 for control, P less than 0.005) of the proximal tubules. Additionally, we observed morphological changes under light microscopy to examine the relationship between metabolism and morphology. On day 3 following the CDDP treatment, typical acute tubular necrosis was seen primarily localized in the outer stripe of the outer medulla, while on day 7 the lesion appeared to be recovering. Our data imply a prominent dissociation between renal metabolic and morphologic changes induced by CDDP.

Ammonia↗
PubMed1992

Lipid peroxidation in isolated rat nephron segments.

Elevated levels of lipid peroxides (LPO) in tissues have been considered an index of increased reactive oxygen metabolites, which are important pathological mediators also found in the kidney. By adopting the quantification of malondialdehyde-thiobarbituric acid adduct as a standard, using a fluorometer, a microassay was developed that enabled us to measure LPO in tissue having less than 1 microgram protein. By this method, basal levels of LPO along the rat nephron showed that proximal tubules bear more LPO per millimeter of tubule than distally located segments (approximately 0.2 pmol/mm tubule for proximal tubules and 0.02 for thick ascending limbs) and that S3 was the highest LPO per tissue protein (2.2 +/- 0.1 pmol/microgram protein, n = 8). In addition, the levels of LPO were stimulated by 10 microM phorbol 12-myristate 13-acetate (PMA) in both glomeruli and S3 (P less than 0.001) and in S2 (P less than 0.05). Furthermore, sphingosine (100 microM), a protein kinase C (PKC) inhibitor, totally blocked the LPO increment by PMA without any effect on the basal LPO in glomeruli, suggesting the involvement of PKC in LPO formation. Taken together, the results indicate the applicability of LPO assay to the nephron for evaluation of site-specific nephrotoxic insult and its mechanisms in renal pathophysiology.

Animals↗
PubMed1992

Intrarenal handling of proteins in rats using fractional micropuncture technique.

Previous micropuncture studies on protein handling along the nephron could not exclude the possibility of contamination by extratubular proteins. Thus we developed a fractional micropuncture method. Renal tubules were punctured with an outer puncture pipette, into which an inner collection pipette was inserted repeatedly to collect tubular fluid, usually up to four fractions. The albumin concentration of tubular fluid was highest in the first fraction and gradually decreased to a constant level, indicating physiological albumin concentrations. On the other hand, low-molecular-weight protein (LMWP) concentrations showed no significant difference among the four fractions. By plotting the protein delivery in the fourth fraction along the nephron, glomerular filtrated protein concentrations were estimated by extrapolating the tubular fluid-to-plasma inulin concentration ratio into one. The glomerular filtrated albumin was 22.9 micrograms/ml (0.00062 in filtration coefficient), and that of LMWP was 72.1 (0.988). Albumin was almost evenly reabsorbed in early (37%) and late (34%) proximal convoluted tubules and the straight tubules (23%). On the other hand, LMWP was more strongly reabsorbed in the early proximal convoluted tubules (54%) than in the late ones (28%) or the straight portion (5%). The fractional micropuncture procedure provides direct evidence of protein handling along the nephron without extratubular protein contamination.

Absorption↗
PubMed1992

Biosynthesis of guanidinoacetic acid in isolated renal tubules.

Guanidinoacetic acid, a precursor of creatine, is an essential substrate for muscle energy metabolism. Since guanidinoacetic acid has been reported to be synthesized from arginine and glycine by glycine amidinotransferase (transamidinase) in kidney homogenates or slices, the purpose of this study was to provide evidence of guanidinoacetic acid synthesis in isolated tubules from rat kidneys, and to clarify the mechanism regulating it. Isolated rat tubules were incubated with various substrates. Guanidinoacetic acid was separated by high performance liquid chromatography and measured fluorometrically. Results obtained were as follows: (1) Guanidinoacetic acid was synthesized from arginine or canavanine and glycine in isolated rat tubules. (2) D,L-Norvaline, ornithine and methionine suppressed guanidinoacetic acid synthesis. (3) Creatine suppressed guanidinoacetic acid synthesis, i.e. creatine was a negative feedback inhibitor of guanidinoacetic acid synthesis in this in vitro system. (4) Guanidinoacetic acid was not synthesized from hydroxyurea, citrulline, argininosuccinic acid or canaline. These data demonstrate that guanidinoacetic acid is synthesized only from arginine or canavanine and glycine, and that the guanidine cycle may not function fully in the rat renal tubule.

Animals↗
PubMed1992

Alterations of gluconeogenesis by ischemic renal injury in rats.

This study was designed to determine changes in one metabolic function, gluconeogenesis (GLG), after ischemic renal injury. Tubule suspensions were prepared by collagenase treatment of SD rat kidneys on 1, 3, and 7 days after left renal artery and vein occlusion for 0-90 min and incubated in Krebs-Henseleit buffer with or without 2 mM pyruvate or malate aerobically. Glucose contents were assayed photometrically. On days 1 and 3 after ischemia for longer than 60 min, serum creatinine levels rose significantly. The tendency of increase of GLG was observed on days 1 and 3 after 10-60 min of ischemia. GLG increased significantly on day 1 after 30-min ischemia. On the other hand, GLG decreased significantly on day 1 after 90-min treatment. Morphologic damage was limited to the corticomedullary region on days 1 and 3 after ischemic times of 30 and 60 min. These results suggest that renal GLG is stimulated to supply energy for ATP decrease by ischemia and for further regeneration in extraproximal segments along the nephron.

Acute Kidney Injury↗
PubMed1992

[Usefulness of microdissection of nephron segments and fluorescent indicator for molecular biological studies of nephron functions].

The kidney consists of numerous functional units called nephrons. Thus, the use of individual nephron segments is essential to characterize their functional properties and to clarify the molecular basis of site-specific functions. Nephron segments can be microdissected from collagenase-treated renal slices under a stereomicroscope. A variety of intracellular ionic concentrations or membrane potential can be determined with various fluorescent probes. Fura-2/AM-loaded nephron segments reveal a transient increase of cytosolic free calcium concentrations by agonists such as angiotensin II, vasopressin, kinins, etc. To localize their receptors or to characterize their subtypes, this technique is especially beneficial, because tiny fragments of the nephron are sufficient by combination with a two-wave length microscope fluorometer. As an example, discovery of a novel vasopressin receptor (Vp) is described.

Angiotensin II↗
PubMed1991

A novel vasopressin receptor in rat early proximal tubule.

In order to evaluate the receptor subtypes of arginine vasopressin (AVP) in early proximal tubule (S1), outer medullary thick ascending limb of Henle's loop (MTAL) and collecting tubule (OMCT), the effect of AVP on intracellular free calcium ([Ca++]i) was determined using the fluorescence indicator Fura-2. Physiological concentration (greater than or equal to 10(-12) M) of AVP in MTAL and OMCT mobilized [Ca++]i in a dose-dependent manner, but relatively high concentration (greater than or equal to 10(-9) M) of AVP in S1 increased [Ca++]i. Moreover, pretreatment with both V1 and V2 antagonists in MTAL or OMCT completely inhibited the AVP-induced [Ca++]i transient, but in S1 partially blocked it. Using several AVP analogues, a relative distribution of AVP receptor subtypes was tentatively calculated in each nephron segment, indicating that although these nephron segments possess V1, its density was very low (about 10%). The majority (about 90%) of AVP receptor in MTAL and OMCT was V2, while that in S1 was a new subtype (named Vp) which is insensitive to V1 and V2 antagonists. To evaluate physiological significance of Vp receptor, AVP-mediated cellular ATP change was measured. Cellular ATP content in S1 was significantly increased by 10(-7) M AVP, but in MTAL it was significantly decreased by the same concentration of AVP. This study suggests that a novel AVP receptor exists in isolated rat S1, and its physiological significance may be the inhibition of ATP-consuming ion transport system.

Adenosine Triphosphate↗
PubMed1990

Mercury chloride as a possible phospholipase C activator: effect on angiotensin II-induced [Ca++]i transient in the rat early proximal tubule.

In our previous report (Biochem. Biophys. Res. Commun. 165(3), 1221-1228, 1989), we have demonstrated the biphasic increase of intracellular free calcium concentration ([Ca++]i) induced by angiotensin II (ANG II) in isolated rat early proximal tubule (S1). The present study was undertaken to determine the effect of HgCl2 on ANG II-induced [Ca++]i increase using Fura-2. HgCl2 (10(-10) M2-10(-8) M) potentiated the [Ca++]i increase induced by ANG II (10(-11) M) in a dose-dependent manner. To determine the mechanism of stimulatory effect by HgCl2 on ANG II-induced [Ca++]i increase, nephron segments were pretreated with 10(-4) M propranolol, a phospholipase C inhibitor. The stimulatory effect by 10(-9) M HgCl2 in 10(-11) M ANG II-induced [Ca++]i increase was completely inhibited by propranolol. Moreover, 10(-4) M propranolol completely blocked the stimulatory effect of HgCl2 on ANG II-mediated IP3 production. This study suggests for the first time that HgCl2 stimulates the [Ca++]i increment induced by ANG II, possibly through an activation of phospholipase C.

Angiotensin II↗
PubMed1990

Cerebral and abdominal arterial hemodynamics in preterm infants with patent ductus arteriosus.

Using Doppler echocardiography we evaluated the effect of ductal shunt flow on the cerebral and abdominal arterial blood flow in 25 preterm infants. Eligible for inclusion in this study were healthy preterm newborn infants. They were divided into two groups based on their gestational age: group A, 33-36 weeks (15 infants) and group B, 28-32 weeks (10 infants). Two-dimensional Doppler echocardiograms were obtained in each infant during the first 8 hours of life and repeated every 6-12 hours until no ductal shunt flow could be detected. Flow in the ductus arteriosus, the basilar artery and the coeliac artery were examined. Closure of the ductus arteriosus occurred significantly later (p less than 0.05) in group B than in group A. Pulsatility indices of flow in the basilar and coeliac arteries were high when the ductus was patent, decreasing to a fixed level with closure. This study suggests that a shunt of the patent ductus arteriosus (PDA) adversely influences the cerebral and abdominal blood flow in preterm infants.

Abdomen↗