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A Inoue

Publications and source records attributed to A Inoue.

At least 415 records · Page 23Linked to original sources
PubMed1988

Elementary steps of the actin-activated ATPase reaction of cardiac muscle myosin subfragment-1.

The rates of the elementary steps of the actomyosin ATPase reaction were measured using the myosin subfragment-1 of porcine left ventricular muscle. The results could be explained only by the two-route mechanism for actomyosin ATPase (Inoue, Shigekawa, & Tonomura (1973) J. Biochem. 74, 923-934), in which ATP is hydrolyzed via routes with or without accompanying dissociation of actomyosin. The dependence on the F-actin concentration of the rate of the acto-S-1 ATPase reaction in the steady state was measured in 5 mM KCl at 20 degrees C. The maximal rate, Vmax, and the dissociation constant for F-actin of the ATPase, Kd, were 3.0 s-1 and 2.2 mg/ml, respectively. The Kd value was almost the same as that determined from the extent of binding of S-1 with F-actin during the ATPase reaction. The rate of recombination of the S-1-phosphate-ADP complex, S-1ADPP, with F-actin, vr, was lower than that of the ATPase reaction in the steady state. Thus, ATP is mainly hydrolyzed without accompanying dissociation of acto-S-1 into S-1ADPP and F-actin. In the cardiac acto-S-1 ATPase reaction, the rate of the ATPase reaction in the steady state and that of recombination of S-1ADPP with F-actin were about 1/5 those of the skeletal acto-S-1 ATPase reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Oxygen exchange during the acto-subfragment-1 ATPase reaction: evidence for the two-route mechanism of the actomyosin ATPase reaction.

The oxygen exchange occurring during the acto-S-1 ATPase reaction was analyzed based on the distribution of 18O-labeled species of P1 using [gamma-18O]ATP as a substrate. Evidence was found for the two-route mechanism in which ATP is hydrolyzed via the dissociation of acto-S-1 into F-actin and the S-1-phosphate-ADP complex, S-1PADP, and their recombination, and also hydrolyzed without the dissociation of acto-S-1 (Inoue, A., Shigekawa, M., & Tonomura, Y. (1973) J. Biochem. 74, 923-934; Inoue, A., Ikebe, M., & Tonomura, Y. (1980) J. Biochem. 88, 1663-1677). When ATP was mainly hydrolyzed without the dissociation of acto-S-1, the extent of oxygen exchange was low. When ATP was hydrolyzed by both routes, the distribution of product P1 with 3, 2, 1, and 0 18O atoms showed a mixture resulting from low and high oxygen exchange. The rate of ATPase without the dissociation of acto-S-1 can be estimated from the rate of the overall reaction (v), the rate of recombination of S-1PADP with F-actin (vr), and the extent of dissociation of acto-S-1 (a). The distribution of the P1 species measured was almost equal to that calculated from the ratio of ATP hydrolysis via the two pathways as avr and v-avr, respectively. This result indicates that the rates of the dissociation of acto-S-1PADP into S-1PADP and F-actin and their recombination are much lower than the rate of decomposition of the acto-S-1PADP complex into acto-S-1 + ADP + Pi.

Adenosine Triphosphatases↗
PubMed1988

Salt increases blood pressure with biphasic changes in hypothalamic responsiveness in rats.

Tail-cuff systolic pressures became elevated in male Wistar rats fed chow containing 8% NaCl for 4 weeks. After 4 weeks of salt loading, pressor and sympathetic responses to ventromedial hypothalamic stimulation were larger in salt-loaded rats. When similar experiments were done following sinoaortic denervation, all of the effects previously induced by dietary salt loading persisted. By contrast, after only 1 week of salt loading, pressor and sympathetic responses to hypothalamic stimulation were reduced, instead of being increased. Since circulating plasma volume was increased in week 1, it was considered possible that reduced hypothalamic responsiveness was due to enhanced cardiopulmonary baroreflexes. Supporting this interpretation, bilateral vagotomy reversed the hypothalamic inhibition occurring in week 1. Although neither the site nor mechanism causing sympathetic hyperactivity has been determined, our results indicate that chronic dietary salt loading has biphasic effects on the ventromedial hypothalamus: an initial inhibition in the first week followed by stimulation thereafter. These results could mean that dietary salt loading eventually increases sympathetic activity and thereby induces hypertension by stimulating the ventromedial hypothalamus.

Animals↗
PubMed1988

Structure-activity relationship of hylambatin and its fragments as studied in the guinea-pig ileum.

Hylambatin (Hyl), a dodecapeptide isolated from the skin of the African frog, Hylambates maculatus, belongs to the family of tachykinin or physalaemin-like peptides. Hylambatin and its 12 fragments were tested in the guinea-pig ileum preparation for contractile activities. All fragments except 3 had contractile activities. The C-terminal fragment as short as the octapeptide sequence was at least as active as the parent molecules. The heptapeptide fragment (Hyl6-12) and the hexapeptide fragment (Hyl7-12) were less active and the C-terminal pentapeptide fragment (Hyl8-12) and the N-terminal hexapeptide fragment (Hyl1-6) were much less active. The N-terminal pentapeptide fragment (Hyl1-5) and the N-terminal fragment from which the N-terminal Asp or Asp-Pro residues were removed (Hyl2-6, Hyl3-6), were inactive at doses used.

Animals↗
PubMed1988

[Reaction of various experimental animals to exposure to acetylcholine or histamine, and morphological observations of bronchial smooth muscle].

We investigated the sensitivity of the airway of various experimental animals to acetylcholine (ACh) and histamine (Hist). The experimental animals were exposed to 0.1% ACh or 0.05% Hist. Guinea pigs and rabbits exhibited an asthmatic reaction to both chemicals, but rabbits seemed to have a milder reaction than guinea pigs to both chemicals. Mice, rats and hamsters showed no reaction. We then performed a morphological study of the airways of 5 species in order to clarify the reason for their different reactivities to ACh and Hist. In the morphological study, abundant smooth muscle could be seen in the terminal bronchioles and respiratory bronchioles of guinea pigs and rabbits. In contrast, animals of other species had little smooth muscle in either site. Mice had no respiratory bronchioles. Consequently, we concluded that there is a high correlation between sensitivity to ACh and Hist and the extent of smooth muscle distribution around the airway.

Acetylcholine↗
PubMed1988

The effect of ouabain, insulin, and cyclic AMP on the acidification of luminal fluid in the proximal tubule of bullfrog kidney.

A transient urinary acidification was induced in the bullfrog proximal tubule by the peritubular administration of ouabain (10(-4) M). Insulin (200 mIU/ml) provoked a prolonged decrease of tubular fluid pH (TFpH), whereas dibutyryl cyclic AMP (10(-4) M) produced a transient increase of TFpH. The above data support the view that the urinary acidification in the proximal tubule is not explained by a simple mechanism, such as Na+/H+ exchange.

Amiloride↗
PubMed1988

Effect of tolbutamide and glyburide on cAMP-dependent protein kinase activity in rat liver cytosol.

The effect of sulfonylureas tolbutamide and glyburide on adenylate cyclase- and cAMP-dependent protein kinase (A-kinase) was examined in rat liver cytosol. Both tolbutamide and glyburide inhibited the A-kinase activity in a dose-dependent manner. Half-maximal inhibition was obtained at 10 mM with tolbutamide and at 0.2 mM with glyburide, indicating that glyburide was 50-fold as potent as tolbutamide. Neither tolbutamide nor glyburide affected [3H]cAMP binding to the protein kinase, but both inhibited the activity of catalytic units of the A-kinase. Lineweaver-Burk double-reciprocal plots revealed that the inhibitory effects of these drugs were noncompetitive with respect to the protein substrate histone, as well as to the phosphate-donor substrate ATP. Thus, tolbutamide and glyburide inhibited the A-kinase activity in rat liver cytosol, and it was suggested that, through the inhibition of A-kinase, the sulfonylureas would affect the carbohydrate metabolism in the liver. In fact, the relative potencies of these two drugs on A-kinase activity corresponded well with those of their reported antidiabetic effects.

Adenosine Triphosphate↗
PubMed1988

The function of two heads of myosin in muscle contraction.

Myosin has two heads which can bind with F-actin and react with ATP. The skeletal muscle myosin forms each 1 mol of the myosin-phosphate-ADP complex (M-P-ADP) and the myosin-ATP complex (M-ATP). The actomyosin ATPase reaction which is coupled with muscle contraction is catalyzed only by the head which forms M-P-ADP. However, the function of M-ATP forming head in muscle contraction has not been elucidated. We studied the binding of S-1 and HMM with F-actin and the dissociation of acto-S-1 or acto-HMM by ATP or AMPPNP using the change in light-scattering and fluorescence of pyrene bound to F-actin. S-1 and HMM bound with actin at 1:1 and 1:2 molar ratio, respectively. Acto-S-1 dissociated by one mole of ATP per mole of S-1 but acto-HMM dissociated by 1 mol ATP per mol of HMM (0.5 mol/mol head). Acto-HMM dissociates by AMPPNP (or ADP) via a ternally complex. Acto-HMM bound two mole of AMPPNP, but acto-HMM dissociated by a function of (AMPPNP) but not (AMPPNP)2. These results suggested that the affinity of HMM with F-actin decreased by the binding of one mole of AMPPNP. The result presented here showed that binding of M-ATP forming head with F-actin is controlled by the ATPase reaction of the M-P-ADP forming head. It is suggested that during muscle contraction two heads react cooperatively with thin filament.

Actins↗
PubMed1988

Gas chromatographic method for the quantification of the new calcium antagonist benidipine hydrochloride in plasma using electron capture detection.

A gas chromatographic assay procedure was developed for measuring subnanogram order concentrations of (+/-)-(R*)-2,6-dimethyl-4-(m-nitrophenyl)-1,4-dihydropyridine-3,5- dicarboxylic acid (R*)-1-benzyl-3-piperidinyl ester, methyl ester hydrochloride (benidipine hydrochloride, KW-3049) in plasma. KW-3049 yielded the oxidation product partially during gas chromatography. To avoid decomposition, KW-3049 was oxidized in advance by nitrogen dioxide, extracted by diethylether under alkaline condition, chromatographed on the OV-1 column and measured using electron capture detector.

Animals↗
PubMed1988

Determination of the calcium antagonist benidipine hydrochloride in plasma by sensitive radioimmunoassay.

A sensitive radioimmunoassay of the 1,4-dihydropyridine calcium channel blocker (+/-)-(R*)-2,6-dimethyl-4-(m-nitrophenyl)-1,4-dihydropyridine-3,5-dicarb oxylic acid (R*)-1-benzyl-3-piperidinyl ester, methyl ester hydrochloride (benidipine hydrochloride, KW-3049) has been developed. Antiserum against KW-3049 was produced in rabbits by immunization with an immunogen prepared by conjugating a derivative of KW-3049 to bovine serum albumin. This antiserum was found to specifically bind to [3H]-KW 3049, while the recognition to [3H]-nitrendipine, another well-known dihydropyridine calcium channel blocker, was less pronounced. With the antiserum, [3H]-KW-3049 and dextran coated charcoal, this radioimmunoassay could detect 39 approximately equal to 500 pg/tube of KW-3049 in a buffer system, and 156 to 5000 pg/ml of KW-3049 in plasma by using 0.5 ml of the plasma which was pretreated with MeOH for deproteinization and extracted with diethyl ether under alkaline condition. To assess the specificity of the radioimmunoassay, the inhibition of [3H]-KW-3049 binding to the antiserum by the presumable metabolites was examined. Though three of these presumable metabolites could slightly inhibit the binding of [3H]-KW-3049, they were not detected in rat and dog plasma at 0.5 h after oral administration of KW-3049. Plasma levels of KW-3049 in rats receiving a single oral dose (1 mg/kg) determined by the radioimmunoassay show good agreement with those obtained by gas chromotography.

Animals↗
PubMed1988

Absorption, distribution and excretion after oral administration of 14C-benidipine hydrochloride in rats and dogs.

(+/-)-(R*)-2,6-Dimethyl-4-(m-nitrophenyl)-1,4-dihydropyridine-3,5- dicarboxylic acid (R*)-1-benzyl-3-piperidinyl ester, methyl ester hydrochloride (benidipine hydrochloride, KW-3049) has been developed as antihypertensive and antianginal agent. The absorption, distribution and excretion were investigated after single oral administration of 14C-labeled KW-3049 using Wistar rats and beagle dogs. The results were summarized as follows: 1. After oral administration of 14C-KW-3049 to rats, the plasma radioactivity reached the maximum at 0.5 h, showed the second peak at 4 h and decreased biphasically with the biological half-lives of about 6 h and 38 h. 2. After oral administration of 14C-KW-3049 to dogs, the plasma radioactivity reached the maximum at 1 h and decreased biphasically with the biological half-lives of about 2 h and 25 h. 3. After oral administration to rats and dogs, the excretion of the radioactivity in feces and urine during 72 h (rats) and 96 h (dogs) were 74% and 19%, 66% and 25%, respectively. The radioactivity excreted in the bile was 34% during 48 h and was followed by partial reabsorption from the gastrointestinal tract. 4. High radioactivities were observed in the digestive organs, mesenteric lymphnodes, liver, pancreas, urinary bladder, fat tissue, kidney and spleen after oral administration to rats.

Administration, Oral↗