Biomedical subjects

N Kohashi

Publications and source records attributed to N Kohashi.

21 records · Page 2Linked to original sources

PubMed1976

Purification and some properties of rat liver cysteine oxidase (cysteine dioxygenase).

Cysteine oxidase (cysteine dioxygenase, EC 1.13.11.20) was purified approximately 1000-fold from rat liver. The purified enzyme (protein-B) was obtained as an inactive form, which was activated by anaerobic preincubation with L-cysteine. The active form of protein-B was inactivated during aerobic incubation to produce cysteine sulfinate. This inactivation of protein-B was protected by a distinct protein in rat liver cytoplasm, namely stabilizing protein (protein-A). The Ka and Km values for L-cysteine were 0.8-10(-3) M and 1.3-10(-3) M respectively. The enzyme was strongly inhibited by Cu+ and/or Fe2+ chelating agents but not by Cu2+ chelating agent. The optimum pH of enzyme reaction was 8.5-9.5 while that of enzyme activation was 6.8-9.5, with a broad peak.

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PubMedDate not supplied

Rat atrial natriuretic peptides inhibit oxygen consumption by rat kidney.

The inhibitory effect of high and low molecular weight native and synthetic rat atrial peptides on oxygen consumption in isolated rat kidney mitochondria and slices was measured. Oxygen consumption by mitochondria was measured in the presence of succinate and/or adenosine diphosphate, furosemide, and low and high molecular weight native and synthetic rat atrial peptides. After the addition of succinate, adenosine diphosphate limiting respiration (State 4) increased in the presence of low, but not high, molecular weight native rat atrial peptides. Furosemide caused a significant decrease in State 4 respiration (p less than 0.001). Angiotensin II and arginine vasopressin did not alter State 4 respiration. The rate of oxygen consumption after the addition of saturating adenosine diphosphate in the presence of saturating succinate (State 3 respiration) was reduced by low and high molecular weight native rat atrial peptides. Furosemide completely blocked oxygen consumption after the addition of adenosine diphosphate. Oxygen consumption was unchanged by trypsin treated (natriuretically inactive) low molecular weight rat atrial peptides and ventricular protein extracts of high and low molecular weight native rat atrial peptides. Synthetic and low molecular weight native rat atrial peptides had similar effects on mitochondrial oxygen consumption. Low molecular weight native and synthetic rat atrial peptides decreased the adenosine diphosphate to oxygen ratio, and these peptides, as well as furosemide, also induced mitochondrial swelling; none of the other rat atrial peptide combinations nor angiotensin II produced this effect. In kidney slices, basal oxygen consumption (without substrates) was stimulated by succinate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate↗

PubMedDate not supplied

Rat platelets activate high molecular weight atrial natriuretic peptides in vitro.

Evidence suggests that the more biologically active low molecular weight forms (less than 10,000) of rat atrial natriuretic peptides are proteolytically derived from a less active precursor of higher molecular weight. Conversion and activation could occur within the myocyte as well as during circulation. The present study found that in vitro rat blood and platelets were capable of converting the high molecular weight atrial natriuretic peptides (greater than 10,000) to low molecular weight atrial natriuretic peptides within minutes and that enhanced biological activity attended the conversion. Rat high molecular weight peptides were partially purified by gel filtration, lyophilized, and reconstituted in Krebs-Ringer bicarbonate buffer. One milliliter of fresh rat blood was incubated with the high molecular weight peptides at 37 degrees C for 2 minutes. After centrifugation, the supernatant was fractionated on Sephadex G-75. Natriuretic activity was determined by bioassay in anesthetized rats. In contrast to the results following incubation of high molecular weight peptides in Krebs-Ringer bicarbonate buffer alone, which showed that 95% of the natriuretic activity remained in the high molecular weight peptide region, the natriuretic activity of the blood-treated high molecular weight peptides eluted almost exclusively in the low molecular weight peptide region, which indicates conversion. Blood was separated into plasma, erythrocytes, lymphocytes, and platelets. Conversion of high to low molecular weight peptides occurred only after incubation with platelets. Compared with control high molecular weight peptides, rat platelet-treated high molecular weight peptides had significantly greater activity in relaxing histamine-contracted rabbit aortic smooth muscle (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

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