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O Kurauchi

Publications and source records attributed to O Kurauchi.

At least 73 records · Page 4Linked to original sources
PubMed1990

Effects of low molecular weight peptides and divalent cations on degradation and binding of angiotensin II.

The effects of peptide inhibitors (bestatin and amastatin) and divalent cations (Ca2+ and Co2+) on the velocity of Asp1 liberation from angiotensin II (A-II) by human placental membrane fractions and binding of 125I A-II to human placental membranes were tested at 22 degrees C and 4 degrees C. Asp1 liberation was measured by high performance liquid chromatography. As expected, the degradation and binding of A-II were temperature sensitive, with both being at 4 degrees C than at 22 degrees C. While amastatin (10(-4) M) and bestatin 10(-6) M) significantly reduced the velocity of Asp1 liberation from A-II to about 45%, amastatin (10(-4) M) and bestatin (10(-4) M) increased 125I A-II binding to 125% and 130%, respectively. Ca2+ (10 mM) and Co2+ (10 mM) activated the velocity of Asp1 liberation from A-II to 140% and 120%, respectively at 22 degrees C. Ca2+ (10(-1) M) and Co2+ (10 mM) also enhanced 125I A-II binding about 130%. Previously we showed that the A-II degrading activity found in human placental membrane fractions is mainly due to aminopeptidases A and M. Since amastatin and bestatin are the specific inhibitors for aminopeptidases A and M, and since Ca2+ and Co2+ are the activators for aminopeptidase A and aminopeptidase M, respectively, it is conceivable that the enzymes regulate the levels of A-II and, therefore, that they may play an important role in the binding of A-II to human placental membrane fractions.

Adult↗
PubMed1990

A comparison of the binding of angiotensin II to human placenta between normal and severe pre-eclamptic pregnancy.

We compared the binding of angiotensin II (A-II) to human placenta between normal and severe pre-eclamptic pregnancy. Our data did not show any statistically significant difference between normal and pre-eclamptic pregnancy in both the equilibrium dissociation constant (Kd) and the total number of placental A-II receptors. Therefore, changes in the binding of A-II to placenta might not be involved in the possible cause of activation of the renin-angiotensin system in the feto-placental unit in severe preeclampsia.

Aminopeptidases↗
PubMed1989

Effects of progesterone and estradiol on aminopeptidase A (AAP) and leucine aminopeptidase (LAP) activities in the pregnancy serum and placenta of the rat.

We investigated the effects of estradiol and progesterone on placental aminopeptidase A and leucine aminopeptidase activities in pregnant rats. Estradiol (0.5, 1.0 and 2 mg/day) plus progesterone (5, 10 and 20 mg/day) was given for five days starting from the 16th day. Changes in both enzyme activities in the serum, placental cytosol and microsome caused by the steroids were analyzed. Aminopeptidase A activities in all three compartments and leucine aminopeptidase activities in the serum and cytosol were stimulated by estradiol (1.0 mg/day) plus progesterone (10 mg/day). Since we previously found that the placental aminopeptidases degrade peptide hormones, our present study suggests that steroids effect the metabolism of peptide hormones of fetal and/or maternal origin.

Aminopeptidases↗
PubMed1989

Effects of bestatin on intrauterine growth of rat fetuses.

Pregnant Wistar rats were injected with bestatin, a specific inhibitor of aminopeptidase M. Placental aminopeptidase M activity was inhibited by injection of bestatin, and fetal body weight was statistically lower than that in the saline-injected or control group. Our present data suggest that placental aminopeptidase M plays an important role in fetal growth.

Alkaline Phosphatase↗
PubMed1989

Changes in the binding of angiotensin II to rat placental receptor by estrogen and progesterone.

The effects of estradiol and progesterone on the binding of rat placental angiotensin II receptors were examined. Sex steroid (progesterone estradiol plus progesterone) decreased the total number of rat placental angiotensin II receptors, while sex steroid (estradiol plus progesterone) increased angiotensin levels. Our present results suggest that sex steroids may play an important role in the control of the number of the angiotensin binding sites during pregnancy.

Angiotensin II↗
PubMed1989

Purification and properties of microsomal carboxypeptidase N (kininase I) in human placenta.

Carboxypeptidase N (kininase I, EC 3.4.17.3) was found in human placenta and purified 600-fold. The enzyme was solubilized from membrane fractions with Triton X-100 and was purified by affinity chromatography with histargin, a potent inhibitor of this enzyme. The pH optimum of the enzyme was 7.8. The Km values for L-hippuryl-L-lysine and bradykinin were 1.25 and 0.43 mmol/l, respectively. The apparent molecular mass (Mr) of the enzyme determined by gel filtration was estimated to be 280,000, which is identical to that of the human serum enzyme. We propose that the placenta is a major source of carboxypeptidase N and thus may be involved in the physiological control of fetal circulation by regulating the kallikrein-kinin and renin-angiotensin systems.

Carboxypeptidases↗
PubMed1989

Increased sensitivity to bradykinin in pregnant rats.

We tested the effects of late pregnancy on the depressor response to bradykinin (100, 200 and 400ng) in rats. All experiments were performed under anesthesia by intraperitoneal injection of pentobarbital (50 mg/kg). Catheters were connected to the arterial and venous lines for blood pressure recording and administration of drugs. Late pregnancy (19- to 21-day) showed a hypersensitivity of the depressor response to bradykinin. The effects of captopril, Kininase II inhibitor, on the depressor response to bradykinin were examined in rats. Since captopril (50, 100 and 200 micrograms) notably increased the depressor response to bradykinin both in nonpregnant and 19- to 21-day pregnant rats, kininase II acts as a bradykinin metabolizing enzyme in vivo. Captopril (50, 100, 200 micrograms), however, resulted in the augmented parallel increases of depressor response to bradykinin (100ng) in both nonpregnant and pregnant rats. Our data may suggest that kininase II is not involved in the hypersensitivity to bradykinin in late pregnancy in rats.

Animals↗
PubMed1989

A comparison of the hypotensive effects of Met-enkephalin in normotensive and spontaneously hypertensive rats.

To elucidate the role of Met-enkephalin in the hypertension in spontaneously hypertensive rats, the depressor response to Met-enkephalin was compared between normotensive (Wistar) and spontaneously hypertensive rats by administration of bestatin (1.25 mg) as a component of a mixture of enkephalinase inhibitors. All experiments were performed under anesthesia by intraperitoneal injection of pentobarbital (50mg/kg). Catheters were connected to the arterial and venous lines for blood pressure recording and administration of drugs. Hypotensive effects of injected Met-enkephalin were noticeably enhanced by administration of bestatin compared with pre-bestatin responses at each dose of Met-enkephalin(10, 25, 50, and 100n mol). We could not find any statistically significant difference between blood pressure responses to 25n mole Met-enkephalin in Wistar and spontaneously hypertensive rats both before and after administration of bestatin. Our present study dose not suggest the active role of Met-enkephalin in the hypertension of spontaneously hypertensive rats.

Animals↗
PubMed1988

Positive effect of estradiol and progesterone in severe pre-eclampsia.

We have used estradiol benzoate (E) and Progesterone (P) for the treatment of severe pre-eclampsia and obtained good results in 8 cases. To assess the placental function, we serially measured leucine aminopeptidase (placental type, P-LAP) in serum. As a new trial, we used E and P in place of the hypotensive and diuretic drugs in 8 cases of severe pre-eclampsia. In a typical case, a patient at week 31 of gestation suffered from highly elevated blood pressure (190/130 mmHg) and proteinuria; at this time we started the treatment with E (20 mg/day) and P (80 mg/day), and continued it for 23 days with increasing doses. By this treatment the blood pressure was gradually decreased and the edema improved; the serum P-LAP increased gradually. At week 35, the P-LAP activity decreased suddenly despite the steroid treatment suggesting a placental dysfunction. At this stage we made Cesarean section and a male infant weighing 1.750 g (Apgar score 8) was delivered alive. Until now we have experienced 7 other cases of the successful treatment with the E and P.

Adult↗
PubMed1988

In vitro degradation of opioid peptides by human placental aminopeptidase M.

The degradation of opioid peptides by human placental aminopeptidase M was studied by measuring liberated amino acids by high performance liquid chromatography. The purified placental aminopeptidase M actively degraded Met-enkephalin (Met-Enk) and Leu-enkephalin (Leu-Enk) completely into constituent 5 amino acids. The activities as a function of tyrosine liberation were observed for Met-Enk followed by Leu-Enk, beta-neoendorphin, dynorphin, and beta-endorphin.

Aminopeptidases↗
PubMed1988

Purification and characterization of human placental aminopeptidase A.

Human placental aminopeptidase A (AAP) was purified 3,900-fold from human placenta and characterized. The enzyme was solubilized from membrane fractions with Triton X-100, then subjected to trypsin digestion, zinc sulfate fractionation, chromatographies with DE-52, Sephacryl S-300, and hydroxylapatite, affinity chromatography with Bestatin-Sepharose 4B, and finally immunoaffinity chromatography with the antibody against microsomal leucine aminopeptidase (LAP). Aminopeptidase A was completely separated from leucine aminopeptidase by the immunoaffinity chromatography. The apparent relative molecular mass (Mr) of the enzyme was estimated to be 280,000 by gel filtration. The purified enzyme was most active at pH 7.1 with L-aspartyl-beta-naphthylamide (L-Asp-NA) as substrate; the Km value for this substrate was 4.0 mmol/l in the presence of Ca2+. Human placental aminopeptidase A was markedly activated by alkaline earth metals (Ca2+, Sr2+, Ba2+), but strongly inhibited by metal chelating agents such as EDTA and o-phenanthroline. The highest activity was observed with L-glutamyl-beta-naphthylamide, while only minimal hydrolysis was found with some neutral and basic amino acid beta-naphthylamides.

Aminopeptidases↗
PubMed1987

Effect of microsomal leucine aminopeptidase from human placenta (microsomal P-LAP) on pressor response to infused angiotensin II (A-II) in rat.

The role of microsomal placental leucine aminopeptidase (microsomal P-LAP) in the decreased pressor responsiveness to angiotensin II (A-II) in pregnancy was studied. Appreciable amounts of microsomal P-LAP activity were found in rat placenta. The similar dose to the endogenous activity, of human microsomal P-LAP exogenously administered to rats, resulted in significant decrease in the response to A-II. Bestatin, an inhibitor of the microsomal leucine aminopeptidase administered to pregnant rats, enhanced the A-II response. Therefore our present study suggests such refractoriness in response to A-II in pregnancy is due to increased inactivation by the microsomal P-LAP. It was also suggested that prostaglandins were not involved in such refractoriness by the experiments with indomethacin.

Angiotensin II↗
PubMed1986

Purification and characterization of human placental microsomal aminopeptidase: immunological difference between placental microsomal aminopeptidase and pregnancy serum cystyl-aminopeptidase.

Human placental microsomal aminopeptidase (microsomal PAP) was purified 3,880-fold from human placenta and characterized. The enzyme was solubilized from membrane fractions with Triton X-100 and also trypsin digestion, and subjected to zinc sulfate fractionation, chromatographies with DE-52, hydroxylapatite, Sephacryl S-300 and lentil lectin-Sepharose 4B, and finally affinity chromatography with bestatin-Sepharose 4B. Microsomal PAP was separated from aminopeptidase A (AAP) by affinity chromatography. The apparent relative molecular mass (Mr) of the enzyme was estimated to be 220,000 by high-performance liquid chromatography with an aqueous gel column. The purified enzyme gave almost a single band with a molecular mass of 140,000 by sodium dodecyl sulfate (SDS) gel electrophoresis. The isoelectric point of the enzyme was 5.2. The purified enzyme was most active at pH 8.0 with L-leucine-p-nitroanilide as substrate; the Km value for this substrate was 1.1 mmol/l. The microsomal PAP was immunologically different from the pregnancy serum cystyl aminopeptidase (serum PAP).

Aminopeptidases↗
PubMed1985

Plasma angiotensin I and serum placental leucine aminopeptidase (P-LAP) in pre-eclampsia.

A study was undertaken on serial measurements of plasma angiotensin I (A-I) and serum placental leucine aminopeptidase (P-LAP) activities in normal and pre-eclamptic pregnancy. There was the significant difference in A-I levels between normal and mild pre-eclamptic pregnancy at weeks 30, 35, 37, between normal and severe pre-eclamptic pregnancy at week 37. There were no differences in serum P-LAP between normal and mild pre-eclamptic pregnancy up to week 33, but thereafter the levels for the mild pre-eclampsia were significantly higher than for the normal pregnancy. The P-LAP activity for the severe pre-eclampsia reached its maximum level at week 31. Around this week, the levels for severe pre-eclampsia were significantly higher than in the normal pregnancy. After week 35, the activities decreased precipitously to week 40; the activities for severe pre-eclampsia in late pregnancy at weeks 39 and 40 were significantly lower than in normal pregnancy. The above data support the idea that P-LAP test is useful for prediction or diagnosis of pre-eclampsia.

Adult↗
PubMed1985

In vitro degradation of oxytocin by pregnancy serum, placental subcellular fractions and purified placental aminopeptidases.

The degradation of oxytocin (formula; see text) by human placental particulate and soluble fractions, pregnant and non-pregnant sera, and purified enzymes such as microsomal placental leucine aminopeptidase (P-LAP), retroplacental serum P-LAP and placental post-proline endopeptidase, was studied by measuring liberated amino acids with a high performance liquid chromatograph (HPLC). While the placental particulate fraction degraded oxytocin almost completely into single amino acid and amide, the placental soluble fraction did not liberate any amino acid and amide. Purified retroplacental P-LAP liberated Tyr2, Ile3, Gln4 and Asn5 from the cyclic structure of oxytocin actively. Pregnancy serum containing the retroplacental P-LAP liberated also these amino acids and amides. Purified microsomal P-LAP liberated Leu8 in addition to these amino acids and amides. Although purified placental post-proline endopeptidase or porcine kidney leucine aminopeptidase (LAP) could not liberate any amino acid and amide from oxytocin, the combination of the post-proline endopeptidase with porcine kidney LAP or with placental microsomal P-LAP actively liberated all amino acids and amides detectable by HPLC. When the ratio of amino acid liberation velocity to LAP activity measured with leu-p-nitroanilide was calculated, the ratios for cyclic amino acids such as Tyr2 and Ile3 were high with the placental particulate fraction, the mixture of post-proline endopeptidase and microsomal P-LAP, retroplacental P-LAP, and pregnancy serum. The ratio for Leu8 was high with the placental particulate fraction and the mixture of post-proline endopeptidase and microsomal P-LAP.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1985

In vitro degradation of angiotensin II (A-II) by human placental subcellular fractions, pregnancy sera and purified placental aminopeptidases.

The degradation of angiotensin II (Asp1-Arg2-Val3-Tyr4-Ile5-His6-Pro7-Phe8: A-II) by human placental particulate and soluble fractions, pregnant and non-pregnant sera, and highly purified placental enzymes such as placental leucine aminopeptidase P-LAP (microsomal), retroplacental serum P-LAP (soluble), aminopeptidase A and post-proline endopeptidase, was studied by measuring liberated amino acids by high performance liquid chromatography. Placental particulate and soluble fractions degraded A-II almost completely into single amino acids. The purified P-LAP (microsomal) actively liberated five amino acids from the N-terminal. The placental particulate fraction containing P-LAP (microsomal) also actively liberated these amino acids. The purified aminopeptidase A liberated Asp1 very actively as expected. When the ratio of the velocity of liberation of each amino acid to P-LAP activity measured with leu-p-nitroanilide as a substrate was calculated, placental soluble fraction liberated Asp1 very actively, but the liberation rate of Asp1 with the purified P-LAP (soluble) was very low. Therefore it seems that the enzyme in the placental soluble fraction and pregnancy serum responsible for the Asp1 liberation is not P-LAP (soluble), but aminopeptidase A. The mixture of purified P-LAP (soluble) and aminopeptidase A showed higher liberation rate of Arg2 and Val3 than that with purified aminopeptidase A alone, demonstrating that once the N-terminal Asp1 was liberated, the P-LAP (soluble) attacks the shorter peptide (angiotension III) very actively. It was concluded that P-LAP (microsomal) together with aminopeptidase A seem to contribute greatly to the degradation of A-II in pregnant women.

Amino Acids↗