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Biomedical subjects

T Kokubu

Publications and source records attributed to T Kokubu.

At least 163 records · Page 9Linked to original sources
PubMed1981

Isolation and characterization of angiotensin converting enzyme from human kidney.

Angiotensin converting enzyme [EC 3.4.15.1] was solubilized from the membrane fraction of human kidney cortex using trypsin and purified to homogeneity by DEAE-cellulose, hydroxylapatite and DEAE-Sephadex A-50 column chromatographies, preparative isoelectric focusing, and Sephadex G-200 gel filtration. The final recovery of the enzyme was 13.9%. The molecular weight of the enzyme was estimated to be 199,000 by a sedimentation equilibrium method. A value of 170,000 was obtained for the reduced and denatured enzyme by dodecylsulfate-polyacrylamide gel electrophoresis. The enzyme was a glycoprotein consisting of a single polypeptide chain with an isoelectric point of 5.10. Neutral sugar accounted for 13% per weight of the enzyme. The purified enzyme had a specific activity of 96.9 mumol/min/mg protein for hippurylhistidylleucine. The Km value, Kcat value and hydrolytic coefficient (Kcat/Km) of the enzyme for hippurylhistidylleucine were 2.0 mM, 545 s-1 and 273 mM-1 . s-1, respectively. Rabbit antibody against the human kidney converting enzyme inhibited the activities of the enzymes from human lung and serum as equally as that from human kidney, but not those from sheep, dog, or rat sera. The human kidney and lung converting enzymes were immunologically identical on double immunodiffusion analysis.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1981

Effects of angiotension II, thyroxine and estrogen on plasma renin substrate concentration and renin substrate production by the liver.

The effects of angiotensin II, thyroxine and 17 beta estradiol on plasma renin substrate concentration in rats and renin substrate production by perfused rat livers were investigated. The addition of angiotensin II (1-10 microgram) to the perfusion system did not affect the synthesis of renin substrate. After treatment with thyroxine (2.5 mg/kg/day), plasma renin substrate concentration, plasma renin activity, plasma aldosterone concentration and the rate of renin substrate synthesis were all significantly increased. 17 beta estradiol (2 mg) raised both plasma renin substrate concentration and the amount of renin substrate production by the liver. Isoelectric focusing profiles of renin substrate of liver perfusate and of plasma from estrogen-treated rats were different from that of liver perfusate from normal rats. But the profile of renin substrate in plasma was essentially similar to those to liver perfusates both in normal and estrogen-treated rats.

Angiotensin II↗
PubMed1981

Effects of a single administration of captopril on hemodynamics and serum angiotensin converting enzyme activity, plasma renin activity and plasma aldosterone concentration in hypertensive patients.

Hemodynamic responses and behaviors of the renin-angiotensin-aldosterone system to a single administration of captopril (50 mg) were studied in 16 hypertensive patients (essential hypertension, n = 10; renovascular hypertension, n = 3; primary aldosteronism, n = 2; Cushing's syndrome, n = 1). In 10 essential hypertensive patients, the immediate blood pressure reduction caused by decreased total peripheral resistance after the administration of captopril was observed without changes of cardiac output and heart rate. Serum angiotensin converting enzyme activity and plasma aldosterone concentration significantly decreased, whereas plasma renin activity significantly elevated 2 hours after the administration of captopril. The close relationship between the pretreatment value of plasma renin activity and the maximum decrease in mean blood pressure in 16 hypertensive patients suggests that the depressor response to a single administration of captopril could evaluate the degree of angiotensin II dependency in the maintenance of high blood pressure in various types of hypertension.

Adult↗
PubMed1980

Effects of captopril (SQ 14, 225) on the renin-angiotensin-aldosterone system in normal rats.

High doses of captopril (SQ 14, 225) (120-160 mg/kg/day) were administered orally to normal rats, and the effects on the renin-angiotensin-aldosterone system were observed. Plasma angiotensin converting enzyme (ACE) activity was elevated significantly on the 3rd, 7th and 30th days of captopril administration. ACE activity in the lung and the kidney was significantly decreased on the 1st day then gradually increased, becoming significantly higher than that of controls by the 30th day. Plasma renin activity (PRA) was significantly elevated on the 1st day and remained at a high level until the 30th day. Renal renin content was found to be significantly lower on the 1st and 3rd days. Plasma aldosterone concentration was not affected by captopril treatment, whereas serum potassium concentration was found to be significantly lower on the 1st, 3rd and 30th days. It is suggested that besides its inhibitory action on ACE, captopril has a direct or indirect stimulating action on ACE production as well as on renin release.

Aldosterone↗
PubMed1980

Immunological characterization of human membrane-bound arylamidases from small intestine, lung, kidney, liver, placenta and renal cell carcinoma.

Anti-placental and anti-kidney membrane-bound arylamidase antibodies were prepared in rabbits. Both antibodies showed similar titration curves against both the original antigens, and the membrane-bound arylamidases partially purified from small intestine, lung, liver and renal cell carcinoma. Double immunidiffusion tests showed that six membrane-bound arylamidases were immunochemically indistinguishable.

Adenocarcinoma↗
PubMed1980

Angiotensin-converting enzyme in human prostate.

The activity of angiotensin-converting enzyme in human prostate was measured by spectrophotometric method using Hippuryl-L-histidyl-L-leucine (Hip-His-Leu) as substrate. Benign hypertrophic prostate had significantly higher concentration of angiotensin-converting enzyme (1.99 +/- 0.36 (S.E.M.) units/g of tissue, n = 13) than normal prostate (0.44 +/- 0.1 units/g of tissue, n = 5) (p less than 0.01). More than 80% of the enzyme activity occurred in soluble fraction of normal and hypertrophied prostates. Human prostatic angiotensin-converting enzyme, partially purified from benign hypertrophic prostates, had an apparent molecular weight of 290,000 and pI of 4.1. Optimum pH of the enzyme with KM value of 1.0 mmol/l was 7.8 in 0.1 mmol/l borate/sodium/carbonate buffer. The enzyme was competitively inhibited by captopril (Ki, 1.8 nmol/l).

Chlorides↗
PubMed1980

Effects of prostaglandins on renin substrate production by the liver.

1. The effects of prostaglandin (PG) E1, PGE2 and PGF2 alpha on plasma renin substrate concentration in rats and renin substrate production by perfused rat liver were investigated. 2. After bilateral nephrectomy, both plasma renin substrate concentration and renin substrate production were remarkably elevated. 3. The increase in plasma renin substrate level and production of renin substrate by the liver after nephrectomy was markedly suppressed by the treatment with PGE1 or PGE2. 4. In contrast PGF2 alpha had no suppressive effect on renin substrate synthesis. 5. These findings suggest that PGE1 and PGE2 might be inhibitory factors in the regulation of renin substrate synthesis.

Angiotensinogen↗
PubMed1980

Isolation and characterization of membrane-bound arylamidases from human placenta and kidney.

Membrane-bound arylamidases (EC 3.4.11.2) from human placenta and kidney were purified. The enzymes were solubilized from membrane fractions using trypsin. Purification procedures included DEAE-cellulose column chromatography, concanavalin-A--Sepharose 4B column chromatography, hydroxyapatite column chromatography and Sephadex G-200 gel filtration. The final recoveries of placental and kidney enzymes were 22.0% and 20.8% respectively. Polyacrylamide gel electrophoresis, analytical isoelectric focusing, immunoelectrophoresis and ultracentrifugation indicated the homogeneity of both purified enzymes. Equilibrium ultracentrifugation showed molecular weights of 193000 for placental enzyme and 211000 for kidney enzyme. Electrophoresis of the enzymes under denaturing conditions on dodecylsulfate/polyacrylamide gel indicated that each enzyme was a dimer consisting of two identical subunits. Isoelectric points of placental and kidney enzymes were 4.20 and 4.32 at 4 degrees C, respectively. The amino acid compositions of the two membrane-bound arylamidases were similar. The carbohydrate accounted for 18.2% of placental enzyme and 17.4% of kidney enzyme. The purified placental enzyme had a specific activity of 60.1 mumol min-1 (mg protein)-1 and the kidney enzyme had a specific activity of 96.4 mumol min-1 (mg protein)-1. Kcat values of placental and kidney enzymes were 187.8 s-1 and 328.6 s-1, respectively. The hydrolytic coefficient (Kcat/Km) of placental enzyme for L-alanyl-beta-naphthylamide was 2159 mM-1 s-1 and that of kidney enzyme was 3778 mM-1 s-1. Rabbit antibodies against placental and kidney membrane-bound arylamidases inhibited the activities of the corresponding antigens, but the inhibitions were never complete. Three membrane-bound arylamidases from placenta, kidney and renal cell carcinoma were immunochemically indistinguishable.

Amino Acids↗
PubMed1980

Serum angiotensin-converting enzyme activity as an indicator of prognosis in sarcoidosis.

The relationship between the clinical course of sarcoidosis and serum angiotensin-converting enzyme (EC 3.4.15.1) activity was analyzed by observing 51 patients with sarcoidosis during a period of more than 1 yr. The patients were grouped into 3 categories irrespective of treatment: (1) sarcoid lesions in the chest disappeared within 1 yr, (2) sarcoid lesions remained for more than 1 yr with little improvement, (3) sarcoid lesions disappeared within 1 yr, but then relapsed. In group 1 (33 cases), the serum angiotensin-converting enzyme activity decreased from 35.9 +/- 2.0 to 22.0 +/- 1.3 nmol/ml/min after the chest roentgenogram cleared (P less than 0.005). In group 2 (12 cases), the mean serum angiotensin-converting enzyme activity after treatment was not significantly reduced, paralleling the lack of improvement. In group 3 (6 cases), a good correlation was observed between serum enzyme activity and clinical course. These findings indicate that serum angiotensin-converting enzyme activity is an indicator of the clinical course of sarcoidosis.

Adolescent↗
PubMed1980

Isolation and characterization of human renin substrate.

Human renin substrate (angiotensinogen) was purified from outdated bank plasma. Purification procedures included ammonium sulfate precipitation, DEAE-cellulose column chromatography, concanavalin A-Sepharose column chromatography, Hydroxylapatite column chromatography preparative isoelectric focusing and Ultrogel AcA 44 gel filtration. The final recovery was 10% and the specific angiotensin I content of 10.5 micrograms/mg of protein was obtained. Polyacrylamide gel and SDS-polyacrylamide gel electrophoresis and analytical ultracentrifugal analyses showed the homogeneity of the purified renin substrate. The molecular weight of 60900 was determined by sedimentation equilibrium studies. Human renin substrate was a glycoprotein containing 13% carbohydrate. Cystine could not be detected on amino acid analysis. The purified renin substrate showed the isoelectric point heterogeneity (pI, 4.6 and 4.9).

Amino Acid Sequence↗
PubMed1980

Pathophysiological characteristics of labile hypertensive patients determined by the cold pressor test.

Hemodynamic changes during the cold pressor test were examined in Type I labile (juvenile labile) hypertensive patients, Type II labile (middle aged labile) hypertensive patients, established hypertensive patients and normal subjects. In normal, Type I labile hypertensive and established hypertensive subjects, the pressor response during the test was accounted for chiefly by a rise in peripheral resistance. In Type II labile hypertensive patients, an increase in blood pressure during cold stimuli was accompanied by an augmented cardiac output. Therefore, Type II labile hypertension is separated clearly from other types of hypertension with respect to hemodynamic changes during the test. In Type II labile hypertensive patients, however, diazepam reduced an increase in cardiac output during the test, resulting in hemodynamic changes similar to those of normal subjects. After atropinization, the hemodynamic pattern of Type I and established hypertensives changed similar to that of Type II labile patients during the cold pressor test. It is concluded that an excessive cardiac output caused by the cold stimuli is a distinctive hemodynamic characteristics of Type II labile hypertensive patients, and this distinctive hemodynamic characteristics might be due to the decreased parasympathetic tone.

Adult↗
PubMed1980

Effects of insulin and glucagon on production of renin substrate by the isolated rat liver.

An isolated rat liver perfusion system was used to study the effects of insulin and glucagon on renin substrate production. Normal livers synthesized renin substrate at a rate of 28.3 +/- 3.8 (S.E.M.) ng angiotensin I equiv./g liver each h (n = 8). The addition of insulin (more than 0.1 i.u.) to the perfusion significantly enhanced the production of renin substrate which was about twofold higher than normal control values (P less than 0.001). However, glucagon (20 micrograms) did not affect the synthesis of renin substrate. These results indicated that insulin promoted the synthesis of renin substrate by the isolated rat liver.

Angiotensinogen↗