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H Endou

Publications and source records attributed to H Endou.

At least 19 recordsLinked to original sources
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↗
PubMed1990

Intranephron PGE2 production in stroke-prone spontaneously hypertensive rats.

To investigate whether intranephron prostaglandin E2 (PGE2) production in stroke-prone spontaneously hypertensive rats (SHRSP) differs from that in Wistar-Kyoto rats (WKY), we measured PGE2 accumulation rates in microdissected nephron segments from 4- to 6- and 12- to 14-wk-old male rats by radioimmunoassay. In both young and adult WKY, PGE2 accumulation was highest in the papillary collecting duct (PCD) and outer medullary and cortical collecting tubules, intermediate in the glomerulus (Glm), medullary and cortical thick ascending limbs of Henle's loop, and distal tubule, and negligible in the proximal tubule. PGE2 accumulation in adult WKY was severalfold higher than that in young WKY. PGE2 accumulation in adult and prehypertensive young SHRSP was significantly lower than that of respective WKY in most segments, whereas urinary PGE2 excretion was significantly higher in SHRSP than in age-matched WKY. Plasma arginine vasopressin concentrations in adult SHRSP were significantly higher than in WKY. PGE2 accumulation stimulated by 5 microM arachidonic acid was significantly lower in SHRSP than in WKY in most segments of young rats but was lower only in Glm and PCD of adult rats. PGE2 accumulation stimulated by 2 microM Ca2+ ionophore A23187 was significantly lower in most segments of adult and young SHRSP. These results indicate that a decrease in renal tubular PGE2 productive activities in SHRSP might not be caused by secondary adaptation to hypertension.

Aging↗
PubMed1990

Inhibitory effect of phorbol ester on sodium transport in frog urinary bladder.

To confirm the role of protein kinase C (PKC) on epithelial Na transport, we studied the effects of phorbol 12-myristate 13-acetate (PMA) and dioctanoylglycerol (DiC8), activators of PKC, on short-circuit current (Isc) in frog urinary bladder and further examined the influence of sphingosine, an inhibitor of PKC, on PMA- or DiC8-modulated Isc. PMA reduced basal Isc in a dose-dependent manner, and sphingosine (10 and 100 microM) partially restored PMA-reduced Isc. On the other hand, DiC8 (5 x 10(-5) M) also reduced basal Isc, and this action was completely prevented by 100 microM sphingosine. Both PMA (4 x 10(-5) M) and DiC8 inhibited vasopressin (50 mU/ml)- and forskolin (5 x 10(-5) M)-stimulated increases in Isc. PMA (4 x 10(-5) M) also inhibited 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP)-stimulated increase in Isc. Furthermore, PMA (4 x 10(-5) M) and DiC8 (5 x 10(-5) M) inhibited vasopressin (50 mU/ml)-stimulated cAMP accumulation. DiC8 also inhibited forskolin-stimulated cAMP accumulation. These results indicate that PMA exerts inhibitory influence on Na transport mainly by its own potency of PKC activation. In addition, it is suggested that there is a cross talk in epithelial Na transport between PKC and cAMP-dependent pathway in frog urinary bladder.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1990

Furosemide acts on short loop of descending thin limb, but not on long loop.

In order to elucidate the tubular sites of action of loop diuretics such as furosemide, bumetanide and ethacrynic-cysteine complex within isolated rat descending thin limbs, cellular ATP was measured by luciferin-luciferase technique. When short descending thin limbs of Henle's loop (SDL) were incubated in the absence of exogenous substrate at 37 degrees C, cellular ATP content was decreased in a time-dependent manner (up to 49% after 60 min). This ATP decrease, however, was retarded significantly in the presence of loop diuretics at 60 min. The mean percentage of change in ATP compared with the control for each loop diuretic in SDL was as follows: 10(-5) M furosemide, 178%; 10(-5) M bumetanide, 189%; and 10(-7) M ethacrynic-cysteine complex, 154%; respectively. To the contrary, cellular ATP in long descending thin limb of Henle's loop (LDL) was not changed by loop diuretics compared with the control. A similar protection against ATP depletion was observed in the medullary thick ascending limb of Henle's loop, in which the mean percentage was as follows: 10(-5) M furosemide, 163%; 10(-5) M bumetanide, 187%; and 10(-7) M ethacrynic-cysteine complex, 134%. Similarly to LDL, the cellular ATP did not change in outer medullary collecting tubule. From these results, we conclude that loop diuretics act on the isolated rat SDL, but not on LDL.

Adenosine Triphosphate↗
PubMed1989

Biphasic increasing effect of angiotensin-II on intracellular free calcium in isolated rat early proximal tubule.

In the freshly isolated early proximal tubule (S1), the effect of angiotensin II (ANG II) on cytosolic Ca++ concentration ([Ca++]i) was determined using the fluorescent indicator fura-2. In order to establish an adequate experimental system, we investigated firstly the relationship between cellular ATP and [Ca++]i under various conditions in late proximal tubule, the most fragile nephron segment, and cortical collecting tubule, a relatively stable one. We found out that cellular ATP depletion caused [Ca++]i to rise, and ANG II response to [Ca++]i under high ATP condition was higher than that under low ATP condition. ANG II-induced [Ca++]i rise in S1 was biphasic, demonstrating the two peaks corresponding to the 10(-11) and 10(-7) M ANG II. This study suggests for the first time 1) the necessity of high intracellular ATP to evaluate a high affinity ANG II actions and 2) the biphasic characteristics of [Ca++]i increase by ANG II in intact S1.

Adenosine Triphosphate↗
PubMed1989

Inhibitory effect of cyclic AMP on phorbol ester-stimulated production of reactive oxygen metabolites in rat glomeruli.

Studies were conducted to investigate cross-talk between protein kinase C (PKC) and cyclic AMP (cAMP) pathways using rat glomeruli (Glm). Phorbol 12-myristate 13-acetate (PMA), a PKC activator, stimulated production of reactive oxygen metabolites (ROM) in Glm. Forskolin and dibutyryl cAMP (Bt2cAMP) inhibited production of ROM dose-dependently. In the presence of both Bt2cAMP and 3-isobutyl-1-methylxanthine (IBMX) an additive effect was observed. Forskolin at 10(-4) inhibited translocation of PKC from the cytosol to the membrane. These results demonstrate that cAMP-mediated inhibition can occur at a step distal to PKC activation.

1-Methyl-3-isobutylxanthine↗