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K Takaichi

Publications and source records attributed to K Takaichi.

16 recordsLinked to original sources
PubMed2000

Malignant insulinoma which expressed a unique creatine kinase isoenzyme: clinical value of arterial embolization as a palliative therapy.

A 76-year-old man with hypoglycemic coma was diagnosed as malignant insulinoma with multiple hepatic metastases. Embolization was done for two-thirds of the hepatic mass and it rapidly lowered the serum immunoreactive insulin. He was discharged without medication and has been free from hypoglycemia. After the embolization, the serum creatine kinase (CK) level increased transiently although there was no evidence of myocardial infarction. On electrophoresis, the CK activity showed an abnormal peak, suggesting mitochondrial CK. CK release after embolization has been reported in only a few cases with endocrine tumors, which might indicate some relationship between active energy metabolism and mitochondrial CK.

Aged↗
PubMed1999

Expression of transfected human Na+/H+ exchanger (NHE-1) in the the basolateral membrane of opossum kidney cells.

Some epithelial cells have Na+/H+ exchanger (NHE) activity in both apical and basolateral membranes. Amiloride-sensitive NHE-1 is generally identified in the basolateral membrane. The renal cell line, OK7a, targets amiloride-resistant NHE predominantly to the apical membrane. It is controversial whether the transfected NHE-1 is targeted preferentially to the basolateral membrane in OK7a cells, when human NHE-1 is chronically expressed under control of constitutively active promoters. We tried to identify the membranes in which the transfected human NHE-1 could be detected following acute expression in OK7a cells. We have always observed small Na(+)-dependent pH recovery in the basolateral membrane in OK7a cells. It is, however, controversial whether or not OK7a cells express NHE activity in the basolateral membrane. We also characterized Na(+)-dependent pH recovery in the basolateral membrane. It was not inhibited by [4,4'diisothiocyanatostilbene-2,2'-disulfonic acid] (DIDS), [4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid] (SITS), or contralateral amiloride. Li+ but not K+, chol+, or NMG+ could replace Na+. These results are consistent with the presence of the NHE in the basolateral membrane. NHE activities were predominant in the apical membrane and those in both membranes were resistant to amiloride analogs. After stable transfection with human NHE-1 in a vector utilizing the metallothionein promoter, overnight induction with Zn(2+)increased the NHE activity and its sensitivity to amiloride only in the basolateral membrane in OK7a cells. We conclude that the transfected human NHE-1 is exclusively targeted to the basolateral membrane of OK7a cells during acute induction.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1998

Significant reduction of the large-vessel blood volume by food intake during hemodialysis.

Postprandial hypotension during hemodialysis is a serious problem. The reduction of the blood volume (BV) by ultrafiltration and the redistribution of the blood from the large vessels to the splanchnic organs are regarded to be the principle mechanisms of postprandial hypotension during hemodialysis. The hematocrit (Ht) of the large vessels is expected to increase by ultrafiltration and also by peripheral shift of the blood, because Ht of the peripheral vessels is much less than Ht of the large vessels. To analyze the effects of food intake during hemodialysis on BV of the large vessels quantitatively, we monitored Ht of the arteriovenous shunt blood continuously in the patients treated with hemodialysis regularly and estimated BV using the following equation, i.e., BV/initial BV = initial Ht/Ht. The rate of ultrafiltration was kept constant during the study. The reduction rate of BV was expressed as percentage of the initial BV per hour (delta BV). Ultrafiltration rate was expressed as percentage of the dry weight per hour (delta BV), delta BV was 3.24 +/- 0.57%/h (mean +/- SE) before the meal and increased to 13.99 +/- 0.91%/h almost instantaneously when the meal started in the supine position. The minimum value of BV was less than that estimated from the ultrafiltration rate by 2.65 +/- 0.26% of the initial BV. The effects of food intake disappeared in 43 +/- 3 minutes. When the meal was taken in the sitting position, delta BV was 28.21 +/- 2.14%/h, and the minimum value of BV was less than that estimated from the ultrafiltration rate by 4.69 +/- 0.70% of the initial BV. We conclude that food intake during hemodialysis decreases BV of the large vessels transiently but significantly. The effects of food intake on BV were more severe when the meal was taken in sitting position than those when the meal was taken in supine position.

Adult↗
PubMed1997

Na+/H+ exchanger (NHE) in the basolateral membrane is encoded by NHE-1 mRNA in LLC-PK1 clone 4 cells.

Several isoforms of Na+/H+ exchanger (NHE-1-5) have been identified. LLC-PK1 clone 4 (CL4) expresses the amiloride-sensitive type of NHE predominantly in the basolateral membrane, which is believed to be NHE-1. It is not clear whether CL4 expresses NHE in the apical membrane and which side of NHE is encoded by the NHE-1 mRNA. Using acidified CL4 cells on the filter membrane, we examined Na(+)-dependent pH recovery of the apical and basolateral membranes separately. Na+ applied to the apical membrane recovered cell pH. Na(+)-dependent pH recovery in the apical membrane was not inhibited by SITS, DIDS, or contralateral amiloride. Li+ but not K+, chol+, or NMG+ could replace Na+. These data are consistent with the presence of NHE in the apical membrane. Transfection with an antisense oligonucleotide corresponding to the 5' terminal site of NHE-1 cDNA of CL4 decreased NHE activity in the basolateral membrane but not in the apical membrane. We conclude that CL4 expresses NHE activities in both apical and basolateral membranes and that NHE-1 mRNA encodes NHE only in the basolateral membrane.

Animals↗
PubMed1993

Cytosolic pH sensitivity of an expressed human NHE-1 Na(+)-H+ exchanger.

These studies examined the effects of protein kinase C activation and calmodulin inhibition on the amiloride-sensitive NHE-1 isoform of the Na(+)-H+ exchanger in defined host cells. Our objective was to define differences in the cellular regulatory responses using a specified isoform of the Na(+)-H+ exchanger. Suspended cells were loaded with 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein (BCECF) and preacidified to a cytosolic pH of 6.2. Wild-type mouse Ltk- cells, human A-431 cells, and mutant mouse fibroblasts stably transfected with the human NHE-1 isoform (LAP+ cells) were examined to define the maximal rate of transport (Vmax) in response to 140 mM external Na+, the Hill stoichiometric coefficient, and the cytosolic pH at which the NHE-1 isoform was half-maximally stimulated (pH50). The mouse NHE-1 isoform had a greater affinity for cytosolic H+ than the human NHE-1 isoforms. Calmodulin antagonism with N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide reduced the Vmax and shifted the pH50 in the acidic direction, especially in the A-431 cells. Protein kinase C stimulation had a similar effect in A-431 cells and little effect in the wild-type (Ltk-) and transfected (LAP+) mouse cells. While the NHE-1 isoform contains several potential phosphorylation sites, the cellular milieu in which the isoform is expressed has an important effect on the modulation of NHE-1 activity.

Amiloride↗
PubMed1992

Cloning, sequencing, and expression of Na(+)-H+ antiporter cDNAs from human tissues.

Two types of Na(+)-H+ antiporter with different sensitivities to amiloride analogues have been identified in mammalian plasma membranes. A human Na(+)-H+ antiporter cDNA was obtained by Sardet and co-workers (C. Sardet, L. Counillon, A. Franchi, and J. Pouysségur. Cell 56: 271-280, 1989) using mutant mouse fibroblasts lacking Na(+)-H+ antiporter transformed with human genomic DNA. However, the amiloride sensitivity of this cloned Na(+)-H+ antiporter was not precisely determined. Furthermore, the reported cDNA sequence may be a chimera of human and mouse genes. Hence we isolated a Na(+)-H+ antiporter cDNA actually expressed in human tissues and characterized its amiloride sensitivity. Our 4 kb cDNA obtained from human kidney cortex contained the identical open reading frame to that previously reported and the entire 3' terminus, which was quite different from that reported. This discrepancy was not due to differences in tissue-specific expression because cDNAs from different human tissues were identical, and single bands were observed under high stringency on Northern blots of various human tissues. Na(+)-H+ antiporter activity of mutant mouse fibroblasts deficient in Na(+)-H+ antiporter activity transfected with the cloned cDNA was very sensitive to amiloride and 5-N substituted analogues of amiloride. Thus the cloned cDNA represents the NHE-1 isoform of the Na(+)-H+ antiporter.

Amiloride↗
PubMed1992

[Na/H antiporter].

Na/H antiporter located in the plasma membrane is mandatory to maintain cell pH. Two isoforms with different sensitivities to amiloride have been identified. They seem to be products from different mRNAs. The amiloride-sensitive form exists in the non-epithelial cells and the basal membrane of the epithelial cells. The amiloride-resistant form is confined in the apical membrane of the epithelial cells and is important for the vectorial transport of HCO3-. The amiloride-sensitive form has been cloned and sequenced. It is a glycoprotein composed of 815 amino acids. Functional analysis of Na/H antiporter by expressing mutant Na/H antiporter cDNA is in progress.

Animals↗
PubMed1988

AVP-sensitive cAMP production is dependent on calmodulin in both MTAL and MCT.

Vasopressin (AVP) plays a key role in maximal urine concentration by stimulating NaCl reabsorption in the medullary thick ascending limbs of Henle (MTAL) and by increasing water permeability in the medullary collecting tubules (MCT). These effects of AVP in MTAL and MCT are mediated by activation of adenylate cyclase. Because effects of high ambient Ca2+ on AVP-sensitive adenosine 3',5'-cyclic monophosphate (cAMP) production are quite different in MTAL and MCT, we examined whether the Ca2+-calmodulin system is involved differently in AVP-sensitive cAMP production in MTAL and MCT of mouse kidney using two dissimilar calmodulin inhibitors, trifluoperazine (TFP) and W-7. TFP and W-7 inhibited AVP-sensitive cAMP production in both nephron segments in a dose-dependent manner with maximal inhibition of both agents being greater than 90%. A half-maximal inhibition by TFP and W-7 was about 45, 100 microM in MTAL and about 40, 40 microM in MCT, respectively. The inhibitory effect of W-5, a chemically similar to W-7 but less potent calmodulin inhibitor, was significantly less than that of W-7 in both nephron segments. TFP and W-7 but not W-5 also inhibited glucagon-sensitive cAMP production in MTAL. W-7 inhibited forskolin-sensitive cAMP production but the inhibition by W-5 was significantly less than that by W-7 in MTAL and MCT. Results suggest that AVP-sensitive cAMP production is MCT.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1988

Inhibitory guanosine triphosphate-binding protein-mediated regulation of vasopressin action in isolated single medullary tubules of mouse kidney.

Vasopressin (AVP) plays a key role in maximal urine concentration by stimulating NaCl reabsorption in the medullary thick ascending limbs of Henle (MAL) and by increasing water permeability in the medullary collecting tubules (MCT). These effects of AVP in MAL and MCT are mediated by cAMP. Alpha 2-adrenergic stimulation in MCT, and high ambient Ca2+ and PGE2 in MAL inhibit AVP-dependent cAMP production and thereby modulate urine concentration. The present study was undertaken to clarify the mechanisms underlying the inhibition of AVP-dependent cAMP production by these agents using microdissected mouse MAL and MCT. Preincubation of MCT and MAL with 1 microgram/ml pertussis toxin for 3 and 6 h, respectively, resulted in ADP-ribosylation of an approximately 41-kD protein, which was presumably an alpha subunit of the inhibitory GTP-binding protein Gi. Epinephrine, 10(-6) M, via alpha 2-adrenergic stimulation, inhibited AVP-dependent cAMP production in MCT. Preincubation of MCT for 3 h with pertussis toxin abolished the inhibition of AVP-dependent cAMP production by epinephrine. High ambient Ca2+ and PGE2 both inhibited AVP-dependent cAMP production in MAL. Preincubation of MAL for 6 h with pertussis toxin abolished the inhibition by high ambient Ca2+ and attenuated the inhibition by PGE2. Preincubation of MCT or MAL with pertussis toxin for 1 h was ineffective in ADP-ribosylation and did not modify the inhibition of AVP-dependent cAMP production by these agents in both nephron segments. Our data suggest that the inhibition of AVP-dependent cAMP production by alpha 2-adrenergic stimulation in MCT, and by high ambient Ca2+ and adrenergic stimulation in MCT, and by high ambient Ca2+ and PGE2 in MAL, is mediated, at least in part, through activation of Gi.

Adenosine Diphosphate Ribose↗
PubMed1986

High Ca2+ inhibits AVP-dependent cAMP production in thick ascending limbs of Henle.

To further gain insights into the mechanisms underlying impaired urine concentration in hypercalcemia, effects of increasing Ca2+ concentrations in the incubation medium on cAMP production in response to 10(-8) M arginine vasopression (AVP) were examined in thick ascending limbs of Henle (MTAL) and collecting tubules (MCT) dissected from outer medulla of mouse kidney. Increasing Ca2+ in the incubation medium from 1.0 mM to either 2.0 mM or 5.0 mM inhibited AVP-dependent cAMP production in MTAL but not in MCT. This inhibition of AVP-dependent cAMP production by 2.0 mM Ca2+ in MTAL was not reversed by verapamil or diltiazem. Also, Ca2+ ionophore A23187 did not inhibit AVP-dependent cAMP production in MTAL in the presence of 1.0 mM Ca2+. Increasing medium Ca2+ from 1.0 to 5.0 mM inhibited cAMP production in MTAL in response to both glucagon and forskolin by the magnitude comparable to that seen in response to AVP. These results show that high Ca2+ inhibits AVP-dependent cAMP production only in MTAL and not in MCT. In addition, the lack of effects of Ca2+ channel blockers and Ca2+ ionophore suggests that high ambient Ca2+ per se may inhibit AVP-dependent cAMP production in MTAL. The fact that high Ca2+ also suppressed cAMP production in response to glucagon or forskolin suggests that Ca2+ may inhibit AVP-dependent adenylate cyclase at postreceptor site(s), one of which is the catalytic unit of the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1986

High Ca2+ inhibits peptide hormone-dependent cAMP production specifically in thick ascending limbs of Henle.

We showed previously that increasing Ca2+ concentration in the incubation medium suppressed cAMP production in response to vasopressin (AVP), glucagon or forskolin in the medullary thick ascending limb of Henle (MTAL) but not in medullary collecting tubules of mouse kidney. In the present study, we examined, using nephron segments dissected from mouse kidney, whether the inhibitory effect of high Ca2+ is specific to MTAL. Increasing Ca2+ in the incubation medium from 1 to 5 mM inhibited cAMP production in response to parathyroid hormone (PTH), calcitonin, AVP or glucagon in cortical thick ascending limbs of Henle (CTAL), but dit not inhibit cAMP production stimulated by PTH or calcitonin in proximal convoluted tubules and that by AVP in cortical collecting tubules. In CTAL, high ambient Ca2+ also inhibited cAMP production stimulated by forskolin. Thus, our present data show that high Ca2+ inhibits cAMP production specifically in thick ascending limbs of Henle but not in the other nephron segments. High ambients Ca2+ may inhibit adenylate cyclase at postreceptor site(s) one of which may be the catalytic unit of the enzyme in TAL.

Animals↗
PubMed1986

[Pharmacokinetics of cefoperazone in end-stage renal failure patients on peritoneal dialysis].

Pharmacokinetics of cefoperazone (CPZ) was examined in 5 patients with end-stage renal failure on maintenance intermittent peritoneal dialysis. Blood levels of CPZ given as a 1 g intravenous bolus injection were not different whether a patient was on or off peritoneal dialysis. Peritoneal clearance of CPZ was 1.6-1.9 ml/min. Blood CPZ levels reached the therapeutic level within 30-120 minutes after an intraperitoneal administration of 1 g CPZ, and remained at the level at least for 3-5 hours. Side effects of CPZ were not observed in any patient. These data indicate that the peritoneal dialysis does not affect blood CPZ levels given intravenously and that effective blood levels of CPZ can be maintained for several hours after an intraperitoneal injection of the drug. Thus, CPZ is considered useful in renal failure patients on peritoneal dialysis.

Adult↗