Biomedical subjects

M Yoshizumi

Publications and source records attributed to M Yoshizumi.

At least 19 recordsLinked to original sources

PubMed1999

Interferon-gamma-mediated inhibition of cyclin A gene transcription is independent of individual cis-acting elements in the cyclin A promoter.

Interferons (IFNs) affect cellular functions by altering gene expression. The eukaryotic cell cycle is governed in part by the periodic transcription of cyclin genes, whose protein products associate with and positively regulate the cyclin-dependent kinases. To understand better the growth inhibitory effect of IFN-gamma on vascular smooth muscle cells (VSMCs), we compared the expression and activity of G1 and S phase cyclins in control and IFN-gamma-treated VSMCs. IFN-gamma treatment did not inhibit the G1 cyclins but did decrease cyclin A protein, mRNA, and associated kinase activity by 85, 90, and 90%, respectively. Nuclear run-on and mRNA stability determinations indicated that this decrease was the result of transcriptional inhibition. To investigate the molecular basis of this inhibition, we examined protein-DNA interactions involving the cyclin A promoter. Electromobility shift assays showed little change with IFN-gamma treatment in the binding of nuclear proteins to isolated ATF, NF-Y, and CDE elements. In vivo genomic footprinting indicated that IFN-gamma treatment changed the occupancy of chromosomal NF-Y and CDE sites slightly and did not affect occupancy of the ATF site. In a previous study of transforming growth factor-beta1-mediated inhibition of the cyclin A promoter, we mapped the inhibitory effect to the ATF site; in the present study of IFN-gamma treatment, functional analysis by transient transfection showed that inhibition of the cyclin A promoter persisted despite mutation of the ATF, NF-Y, or CDE elements. We hypothesize that IFN-gamma inhibits cyclin A transcription by modifying co-activators or general transcription factors within the complex that drives transcription of the cyclin A gene.

Animals↗

PubMed1998

Estrogen attenuates endothelin-1 production by bovine endothelial cells via estrogen receptor.

To investigate the mechanism underlying the antiatherogenic effect of estrogen, we examined the role of estrogen in the regulation of endothelin-1 (ET-1) production by cultured bovine carotid arterial endothelial cells. Treatment of the cells with 17beta-estradiol dose dependently inhibited gene expression and peptide secretion of ET-1. This inhibitory effect of 17beta-estradiol was more marked when ET-1 production was stimulated by transforming growth factor-beta1. Simultaneous addition of ICI 182,780, a pure estrogen receptor antagonist, completely blocked the effect of 17beta-estradiol, indicating that 17beta-estradiol acted via estrogen receptor. These results suggest that reduced ET-1 production by endothelial cells may be involved in the vasoprotective effect of estrogen.

Animals↗

PubMed1998

Cytokine-induced expression of parathyroid hormone-related peptide in cultured human vascular endothelial cells.

Parathyroid hormone-related peptide (PTHrP) is a potent vasodilatory peptide whose expression has been demonstrated in various tissues. The present study was undertaken to examine the regulation of PTHrP expression in cultured endothelial cells derived from human umbilical vein. Immunoradiometric assay revealed that the amount of PTHrP in the conditioned medium was increased by both tumor necrosis factor alpha (TNF-alpha) and interleukin 1beta (IL-1beta) in both a time- and a dose-dependent manner. The induction of PTHrP mRNA was also observed, with a peak after 2 hours of incubation with both TNF-alpha and IL-1beta. Angiotensin II, endothelin-1, and arginine vasopressin had no affect on PTHrP production. Our results suggest that PTHrP produced in vascular endothelial cells in response to cytokines may modulate vascular function as a local factor.

Cells, Cultured↗

PubMed1998

Expression of peroxisome proliferator-activated receptor gamma (PPARgamma) in rat aortic smooth muscle cells.

Peroxisome proliferator-activated receptor gamma (PPARgamma), a member of nuclear receptors, is expressed at a high level in adipose tissue and plays an important role in adipocyte differentiation. In the present study, we identified the expression of PPARgamma in rat aortic smooth muscle cells (RASMC) using reverse transcription-polymerase chain reaction and gel mobility shift assay. In addition, to investigate whether PPARgamma in RASMC is functional or not, we examined the effect of two specific ligands for PPARgamma, a thiazolidinedione anti-diabetic agent, troglitazone, and 15-deoxy-Delta12,14-prostaglandin J2, on the transcriptional activity of PPAR responsive element (PPRE). A significant increase in the activity of PPRE by addition of these ligands was found. These results suggest that in RASMC, target genes for PPARgamma may be activated by specific ligands for PPARgamma through PPRE in their promoters. In conclusion, PPARgamma is expressed and functional in vascular smooth muscle cells.

Animals↗

PubMed1998

Endothelin-1-(1-31), a novel vasoactive peptide, increases [Ca2+]i in human coronary artery smooth muscle cells.

We have previously found that human chymase cleaves big endothelins at the Tyr31-Gly32 bond and produces 31-amino acid long endothelins-(1-31), without any further degradation products. In this study, we investigated the effect of synthetic endothelin-1-(1-31) on the intracellular free Ca2+ concentration ([Ca2+]i) in cultured human coronary artery smooth muscle cells. Endothelin-1-(1-31) increased [Ca2+]i in a concentration-dependent manner (10(-14) to 10(-10) M). This endothelin-1-(1-31)-induced [Ca2+]i increase was not affected by phosphoramidon (N-(alpha-Rhamnopyranosyloxyhydroxyphosphinyl)-L-Leucyl-L-Tryptoph an), an inhibitor of endothelin-converting enzyme. It was, however, inhibited by 10(-10) M BQ123 (Cyclo-(-D-Trp-D-Asp(ONa)-Pro-D-Val-Leu-)), an endothelin ET(A) receptor antagonist, but not by 10(-10) M BQ788 (N-cis-2,6-dimethylpiperidinocarbonyl-L-yMeLeu-D-Trp(COOM e)-D-Nle-ONa), an endothelin ET(B) receptor antagonist. These results suggest that endothelin-1-(1-31) by itself exhibits vasoactive properties probably through endothelin ET(A) receptors. Since human chymase has been reported to play a role in atherosclerosis, endothelin-1-(1-31) may be one of the candidate substances for its cause.

Calcium↗

PubMed1998

Molecular cloning, characterization, and promoter analysis of the mouse Crp2/SmLim gene. Preferential expression of its promoter in the vascular smooth muscle cells of transgenic mice.

Several members of the LIM protein family have important roles in development and differentiation. We recently isolated a rat cDNA encoding a new member of this family, CRP2/SmLIM, that contains two LIM domains and is expressed preferentially in vascular smooth muscle cells (VSMC). To study the molecular mechanisms that regulate VSMC-specific transcription of the Crp2/SmLim gene, we cloned the cDNA and gene of mouse Crp2/SmLim. Mouse Crp2/SmLim is a single copy gene of six exons and five introns spanning approximately 20 kilobases of genomic DNA. By 5'-rapid amplification of cDNA ends and S1 nuclease protection assay, we determined that the transcription start site is an A residue 80 base pairs 5' of the translation initiation codon. A TATA-like sequence is located 27 base pairs 5' of the transcription start site, and there are potential cis-acting elements (GATA, Sp1, AP-2, E box, CCAC box, and GArC motif) in the 5'-flanking sequence. In transient transfection assays in rat aortic smooth muscle cells in primary culture, 5 kilobases of the Crp2/SmLim 5'-flanking sequence generated a high level of luciferase reporter gene activity. By deletion analysis and gel mobility shift assay, we found that the region between bases -74 and -39 of this 5 kilobase DNA fragment binds Sp1 and confers basal promoter activity in the Crp2/SmLim gene. In vitro, the 5-kilobase fragment was active in multiple cell types. In vivo, however, the 5-kilobase fragment directed high level expression of the lacZ reporter gene preferentially in the VSMC of transgenic mice, indicating the presence of VSMC-specific element(s) in this fragment.

Amino Acid Sequence↗

PubMed1998

Effect of angiotensin II on Ca2+ efflux from freshly isolated adult rat cardiomyocytes: possible involvement of Na+/Ca2+ exchanger.

In the present study, we examined the effect of angiotensin II on Ca2+ efflux from freshly isolated adult rat cardiomyocytes. Angiotensin II stimulated the efflux of 45Ca2+ from the cells in a concentration-dependent manner, at least in pharmacological doses of 10(-8) M to 10(-5) M. The 45Ca2+ efflux was inhibited by the type 1 angiotensin II receptor antagonist losartan, but not by the type 2 antagonist PD 123319. Angiotensin II also induced an increase in cytosolic free calcium ([Ca2+]i) and inositol trisphosphate formation within the cardiomyocytes. Angiotensin II-induced 45Ca2+ efflux and the increase in [Ca2+]i were both inhibited by thapsigargin, a specific inhibitor of the sarcoplasmic reticulum Ca2+ pump. The 45Ca2+ efflux was not affected by removal of the extracellular Ca2+ but was dependent on the presence of extracellular Na+. In addition, angiotensin II caused 22Na+ influx into the cells. These results indicate that angiotensin II stimulates Na+-dependent 45Ca2+ efflux from freshly isolated adult rat cardiomyocytes, probably through its stimulatory effect on the plasma membrane type 1 angiotensin II receptors. Angiotensin II-induced increase in [Ca2+]i may cause an activation of Na+/Ca2+ exchange which finally results in the stimulation of 45Ca2+ efflux from the cells. Since it is reported that Na+/Ca2+ exchange is important in calcium homeostasis within the cells, angiotensin II may play some role in the reduction of intracellular Ca2+ from isolated adult rat cardiomyocytes.

Angiotensin II↗

PubMed1998

Human EZF, a Krüppel-like zinc finger protein, is expressed in vascular endothelial cells and contains transcriptional activation and repression domains.

Members of the erythroid Krüppel-like factor (EKLF) multigene family contain three C-terminal zinc fingers, and they are typically expressed in a limited number of tissues. EKLF, the founding member, transactivates the beta-globin promoter by binding to the CACCC motif. EKLF is essential for expression of the beta-globin gene as demonstrated by gene deletion experiments in mice. Using a DNA probe from the zinc finger region of EKLF, we cloned a cDNA encoding a member of this family from a human vascular endothelial cell cDNA library. Sequence analysis indicated that our clone, hEZF, is the human homologue of the recently reported mouse EZF and GKLF. hEZF is a single-copy gene that maps to chromosome 9q31. By gel mobility shift analysis, purified recombinant hEZF protein bound specifically to a probe containing the CACCC core sequence. In co-transfection experiments, we found that sense but not antisense hEZF decreased the activity of a reporter plasmid containing the CACCC sequence upstream of the thymidine kinase promoter by 6-fold. In contrast, EKLF increased the activity of the reporter plasmid by 3-fold. By fusing hEZF to the DNA-binding domain of GAL4, we mapped a repression domain in hEZF to amino acids 181-388. We also found that amino acids 91-117 of hEZF confer an activation function on the GAL4 DNA-binding domain.

Amino Acid Sequence↗

PubMed1998

Changes in plasma free and sulfoconjugated dopamine in patients with congenital heart disease who underwent cardiac operation.

It has been suggested that plasma sulfoconjugated dopamine (DA) may serve as a source or reservoir for free DA in plasma. Moreover, it has also been reported that the plasma levels of conjugated DA may be used as an index predicting heart failure in patients with heart disease. Therefore, in the present study, we have measured the plasma levels of free and sulfoconjugated DA in patients with congenital heart disease who underwent total corrective operations. The patients were divided into two groups with (6 patients with tetralogy of Fallot, TOF) or without (5 patients with ventricular septal defect without pulmonary hypertension, VSD) cyanosis (mean age of 2.11 years). Blood samples were collected before and after operation from the patients, and plasma free and sulfoconjugated DA levels were measured using high performance liquid chromatography. Preoperative levels of free DA in patients in both groups were higher than the level in age matched control subjects. The plasma level of conjugated DA in TOF was higher than that in the controls and was the highest in VSD before operation. DA infusion early after operation caused a rise in plasma free and conjugated DA, however, the levels of increased free DA were lower in the VSD than in the TOF group. After discontinuing DA infusion, the plasma levels of free DA remained higher, while those of conjugated DA decreased to a level lower than the preoperative values in both groups. As the plasma levels of free and sulfoconjugated DA vary with hemodynamics, it was assumed that the difference in the plasma sulfoconjugated DA level between the groups before operation was due to the influence of pulminary blood flow on catecholamine homeostasis. Since the decrease in conjugated DA has been postulated to be an index of sustained heart failure, it is conceivable that it takes a long time for patients who underwent cardiac operations in infancy to recover from heart failure.

Child, Preschool↗

PubMed1998

Extracellulary administered lysophosphatidylcholine causes Ca2+ efflux from freshly isolated adult rat cardiomyocytes.

It has previously been reported that ischemia and reperfusion of the heart cause accumulation of lysophosphatidylcholine (LPC) within the myocardium. While it is known that LPC causes the transient increase of intracellular free Ca2+ concentration ([Ca2+]i) during contraction of cardiac cells, little is known about the mechanism for decreasing [Ca2+]i in cardiomyocytes during LPC accumulation. Since cumulative elevation in [Ca2+]i leads to irreversible injury to cardiomyocytes, elevated [Ca2+]i must be restored to an unstimulated level to maintain cell functions. In the present study, we therefore examined the effect of LPC on Ca2+ efflux from freshly isolated adult rat cardiomyocytes. LPC stimulated the efflux of 45Ca2+ from the cells in a concentration-dependent manner (10(-7)M-10(-5)M). Other lysophospholipids, which are generated from phospholipids of the cell membrane, failed to induce 45Ca2+ efflux from the cells. Dilazep and K-7259, which are known to inhibit the increase in [Ca2+]i caused by LPC, likewise reduced 45Ca2+ efflux caused by LPC addition. Furthermore, the LPC-stimulated 45Ca2+ efflux was not affected by removal of extracellular Ca2+, but was dependent on the presence of extracellular Na+. On the other hand, inhibitors of Na+/Ca2+ exchange, amiloride and 5-(N,N-dimethyl)-amiloride, inhibited LPC induced 45Ca2+ efflux. These results suggest that LPC stimulates extracellular Na(+)-dependent 45Ca2+ efflux from freshly isolated adult rat cardiomyocytes, probably through Na+/Ca2+ exchange on the plasma membrane of the cells.

Adenosine Triphosphate↗

PubMed1998

Endothelin-1 stimulates sodium-dependent calcium efflux from bovine adrenal chromaffin cells in culture.

1. The effect of endothelin (ET)-1 on Ca2+ efflux from cultured bovine adrenal chromaffin cells was examined. ET-1 (10(-7) M) significantly increased intracellular free Ca2+ level ([Ca2+]i), 45Ca2+ uptake and catecholamine secretion in the cells. 2. ET-1 stimulated the efflux of 45Ca2+ from the cells preloaded with 45Ca2+ in a concentration-dependent manner (10(-9)-10(-7) M). This stimulatory effect was inhibited by ET(B) receptor antagonist BQ788, but not by ET(A) receptor antagonist BQ123. Selective ET(B) receptor agonists Suc-[Glu9, Ala11.5]-ET-1 and sarafotoxin S6c (SRTX) also stimulated 45Ca2+ efflux from the cells. 3. ET-1, Suc-[Glu9 Ala11.15]-ET-1 and SRTX increased the level of cyclic GMP in the adrenal chromaffin cells. ET-1 induced an increase in the nitric oxide (NO) level in the cells. The stimulatory effects by which ET- increases NO level and 45Ca2+ efflux were inhibited by NG-monomethyl-L-arginine acetate (L-NMMA), a competitive inhibitor of NO synthase. 4. The 45Ca2+ efflux stimulated by ET-1 was inhibited by deprivation of extracellular Na+, but not by deprivation of Ca2+. 5. These results suggest that ET-1 stimulates an extracellular Na+-dependent Ca2+ efflux through the activation of NO synthase in cultured bovine adrenal chromaffin cells.

Adrenal Glands↗

PubMed1998

Effect of endothelin-1 (1-31) on extracellular signal-regulated kinase and proliferation of human coronary artery smooth muscle cells.

1. We have previously found that human chymase cleaves big endothelins (ETs) at the Tyr31-Gly32 bond and produces 31-amino acid ETs (1-31), without any further degradation products. In this study, we investigated the effect of synthetic ET-1 (1-31) on the proliferation of cultured human coronary artery smooth muscle cells (HCASMCs). 2. ET-1 (1-31) increased [3H]-thymidine incorporation and cell numbers to a similar extent as ET-1 at 100 nM. This ET-1 (1-31)-induced [3H]-thymidine uptake was not affected by phosphoramidon, an inhibitor of ET-converting enzyme. It was, however, inhibited by BQ123, an endothelin ET(A) receptor antagonist, but not by BQ788, an endothelin ET(B) receptor antagonist. 3. By using an in-gel kinase assay, we demonstrated that ET-1 (1-31) activated extracellular signal-regulated kinase 1/2 (ERK1/2) in a concentration-dependent manner (100 pM to 1 microM) in HCASMCs. ET-1 (1-31)-induced ERK1/2 activation was inhibited by BQ123, but not by BQ788 and phosphoramidon. Inhibition of protein kinase C (PKC) and ERK kinase also caused a reduction of ET-1 (1-31)-induced ERK1/2 activation, whereas tyrosine kinase inhibition had little effect. 4. Gel-mobility shift analysis revealed that the ERK1/2 activation was followed by an increase in transcription factor activator protein-1 DNA binding activity in HCASMCs. 5. Our results strongly suggest that ET-1 (1-31) itself stimulates HCASMC proliferation probably through endothelin ET(A) or ET(A)-like receptors. The underlining mechanism of cell growth by ET-1 (1-31) may be explained in part by PKC-dependent ERK1/2 activation. Since human chymase has been proposed to play a role in atherosclerosis, ET-1 (1-31) may be one of the mediators.

Arteries↗

PubMed1998

The impairment of flow-mediated vasodilatation in obese men with visceral fat accumulation.

BACKGROUND: Obesity has been reported to be associated with coronary artery disease and other atherosclerotic diseases. Recently, evidence has accumulated indicating that intra-abdominal visceral fat accumulation contributes to atherogenesis; however, the mechanism underlying this remains to be determined. This study was undertaken to elucidate whether intra-abdominal visceral fat accumulation impairs vascular endothelial function in obese men. METHODS AND RESULTS: Thirty-eight obese men (body mass index (BMI) > or = 26.0), aged 19-64 y (mean age 37.6 +/- 1.8 y) and 23 age-matched non-obese subjects were examined. According to the ratio of the maximum thickness of preperitoneal fat to the minimum thickness of subcutaneous fat (Pmax/Smin) obtained by longitudinal ultrasound scanning in the subxiphoid region in obese men, we divided obese subjects into two categories; visceral (Pmax/Smin > or = 1; n=23) and subcutaneous type (Pmax/Smin < 1; n=15). To investigate endothelial function, we performed ultrasound measurement of the brachial artery diameter non-invasively both at rest and during reactive hyperaemia in the muscle distal to the brachial artery which causes endothelium-dependent vasodilatation. The brachial diameter change was also measured after sublingual administration of nitroglycerin, which causes endothelium-independent vasodilatation. Flow-mediated diameter (D) increase (%FMD; deltaD/D x 100), in the subjects with visceral type obesity (3.09 +/- 0.43%) was significantly lower than those of the subjects with subcutaneous type obesity and non-obese subjects (7.90 +/- 0.51%, 8.91 +/- 0.44%, respectively, P < 0.01). The magnitude of endothelium-independent vasodilatation by nitroglycerin was similar in all groups. On multiple regression analysis, the Pmax/Smin showed a significant inverse correlation with %FMD. CONCLUSIONS: The subjects with visceral type obesity, rather than those with the subcutaneous type, are associated with impaired flow-mediated endothelium-dependent vasodilatation of the brachial artery.

Adipose Tissue↗

PubMed1998

The angiogenic effect of tissue factor on tumors and wounds.

We report a novel function of tissue factor (TF) as an angiogenic factor in malignant and non-malignant cells and tissue. When methylcholanthrene A-induced murine fibrosarcoma (Meth-A sarcoma) was stably transfected with mouse TF (mTF) cDNA (pXT1 expression vector), its vascularization in vivo was significantly enhanced, whereas TF-antisense suppressed the vascularization and tumor growth. In vitro expression of vascular endothelial growth factor (VEGF) was enhanced with stable transfection of mTF (pcDNA3 expression vector) into a mouse fibroblast cell line (NIH3T3). Moreover, in vivo topical transfection of mTF (pcDNA3) showed an enhanced vascularization and healing in a diabetic mouse wound-healing model. This effect of TF as an angiogenic factor might be useful as an antitumor therapy against hypervascular tumors or as a novel agent against delayed wound healing.

3T3 Cells↗

PubMed1998

Effect of amiloride on ischaemia and reperfusion injury in isolated, perfused rat hearts.

The effect of amiloride, a potent inhibitor of Na+/H+ exchange, on ischaemic reperfused rat hearts was studied in order to investigate whether Na+/H+ exchange or Na+/Ca2+ exchange is involved in ischaemia-reperfusion injury, When hearts were pre-ischaemically loaded with 100 microM amiloride, recovery of left ventricular developed pressure was significantly better than in control hearts, whereas recovery of heart rate at 30-min reperfusion was unaffected. Amiloride pretreatment also decreased creatine phosphokinase activity in the coronary effluent and completely abolished occurrence of ventricular arrhythmias during reperfusion. It also inhibited intracellular Na+ accumulation early in reperfusion (within 5 min), whereas in the late stage (from 5 to 30 min), Ca2+ overload was inhibited. The findings suggest that Na+/H+ exchange participates mainly in the early stage of reperfusion injury and the Na+/Ca2+ exchange system, secondary to Na+/H+ exchange, in the late stage. The reduction in post-ischaemic cardiac dysfunction induced by amiloride pretreatment may be attributable to inhibition of the resultant Ca2+ accumulation during reperfusion.

Amiloride↗

PubMed1998

Plasminogen activator inhibitor-1 promoter 4G/5G genotype is not a risk factor for myocardial infarction in a Japanese population.

There is little question that the blood clotting process is triggered and causes the vascular occlusion associated with myocardial infarction. Although it is less clear what part blood coagulation events might play in the etiology of coronary artery disease, impaired regulation of anticoagulation or fibrinolysis might be involved. Among anticoagulant and fibrinolytic factors, an elevated plasma plasminogen activator inhibitor-1 (PAI-1) concentration has been identified as a risk factor for the development of myocardial infarction. An association between one polymorphism of the PAI-1 promoter (4G/5G single nucleotide deletion/ insertion at position -675) and plasma PAI-1 levels was described in 1995. However, most recent studies seem to point to the lack of such an association. This is the first report on the frequency of this polymorphism in the Japanese population with respect to the risk of myocardial infarction. Sixty-six patients with myocardial infarction and sixty-two healthy control patients were chosen for the analysis of the PAI-1 promoter 4G/5G genotype with polymerase chain reaction-single strand conformation polymorphism. Five myocardial infarction patients and six in the control group were homozygous for the 4G/4G genotype. Twenty-eight and 27 4G/5G and 33 and 29 5G/5G genotypes were found in myocardial infarction and control groups, respectively. The total frequencies of the 4G and 5G alleles were approximately 30% and 70% in both control and myocardial infarction groups. In conclusion, the PAI-1 promoter genotype is not a risk factor for myocardial infarction in the Japanese population. This is in contrast to the first report in Caucasians, suggesting an interaction with other genetic or environmental factors which influences the risk of myocardial infarction.

Aged↗

PubMed1998

Changes in plasma free and sulfoconjugated catecholamines during the perioperative period of cardiac surgery: effect of continuous infusion of dopamine.

In order to elucidate the pharmacological properties of the formation of sulfoconjugated catecholamines (CAs) in human plasma, we investigated the changes in the plasma levels of free and sulfoconjugated CA during the continuous infusion of dopamine (DA; 4-6 microg/kg/min for 24 h, followed by 3-4 microg/kg/min for 48 h) in patients who had undergone cardiac surgery. The plasma level of free DA increased immediately after the start of the infusion and reached a plateau within 1 h at a level of about 2000 times the basal value. In the control patients who had received non-cardiac surgery without DA infusion, plasma-free DA increased only 5-fold after their operation. The plasma level of DA sulfate increased linearly for 24 h, to 48-fold of the basal value by DA infusion, whereas it showed only a 2-fold increase in the control patients. After 24 h, due to reduction of the infused DA dose, the level of free DA gradually decreased, whereas the level of DA sulfate remained elevated. The plasma levels of free adrenaline (Ad) and noradrenaline (NA) also increased during the DA infusion, but their levels reached a plateau within 1-2 h. Sulfoconjugated Ad and NA increased progressively until the tapering off of DA infusion. In the control patients, both free and conjugated Ad and NA showed transient increases over 12 h after surgery. These results suggest that sulfoconjugation plays a role in regulating the plasma levels of excess free CA, thereby modifying the cardiovascular effects of circulating CA. Measurement of the increase in plasma conjugated CA may be useful as an index of the increase in free CA in plasma due to the administration of an exogenous form or release of endogenous CA from the tissues.

Adult↗

PubMed1998

Human chymase, an enzyme forming novel bioactive 31-amino acid length endothelins.

We report the novel role of human chymase in the production of bioactive 31-amino acid length endothelins (ETs), which may play a role in allergies and vascular diseases. In the bronchi of asthmatic patients, the vascular tissue in atherosclerosis, and the heart muscle in cardiac hypertrophy, both ET-like immunoreactivity and the accumulation of mast cells significantly increase. Chymase from human mast cells selectively cleaves big ET-1, -2 and -3 at their Tyr31-Gly32 bonds, and produces novel bioactive 31-amino acid length ETs, ETs(1-31), without any further degradation products. However, chymases from other species, human cathepsin G, and porcine alpha-chymotrypsin, degrade big ETs. ETs(1-31) at concentrations between 10(-9) M and 10(-7) M exhibited various contractile potencies in rat tracheae and porcine coronary arteries in a dose-dependent manner. Furthermore, ET-1(1-31) at concentrations between 10(-14) M and 10(-10) M caused a significant increase in the intracellular free Ca2+ concentration. The contractile activity of ETs(1-31) may not be the consequence of conversion to the corresponding ETs(1-21) by phosphoramidon-sensitive ET converting enzyme(s) or other chymotrypsin-type proteases and metallo-endopeptidases, because the contractile activity was not significantly inhibited on treatment with inhibitors of these proteases prior to the addition of ET-1(1-31).

Animals↗