Growth stimulation of ferritin of human leukemia cells in vitro

Ferritin has been reported to inhibit the growth of some leukemia cells in serum-supplemented culture. Recently we have found that ferritin stimulates the proliferation of human acute myeloblastic leukemia cells HL-60 and erythroleukemia cells K-562-T1 in serum-free medium. In this study, we examined the effect of ferritin against 14 human leukemia cell lines using human heart ferritin in serum-depleted culture medium. Among 14 cell lines tested, 10 were stimulated to proliferate by ferritin (maximum response at 30-300 ng/ml) with 0-1% fetal calf serum (FCS). The growth of all the cell lines was significantly inhibited by ferritin in the presence of 10% FCS. These results suggest that ferritin has dual functions; it promotes the growth of leukemia cells with low concentrations of FCS, but suppresses their growth with high concentrations of FCS.

Isolation of a cDNA for a growth factor of vascular endothelial cells from human lung cancer cells: its identity with insulin-like growth factor II

We have found growth-promoting activity for vascular endothelial cells in the conditioned medium of a human lung cancer cell line, T3M-11. Purification and characterization of the growth-promoting activity have been carried out using ammonium sulfate precipitation and gel-exclusion chromatography. The activity migrated as a single peak just after ribonuclease. It did not bind to a heparin affinity column. These results suggest that the activity is not a heparin-binding growth factor (including fibroblast growth factors) or a vascular endothelial growth factor. To identify the molecule exhibiting the growth-promoting activity, a cDNA encoding the growth factor was isolated through functional expression cloning in COS-1 cells from a cDNA library prepared from T3M-11 cells. The nucleotide sequence encoded by the cDNA proved to be identical with that of insulin-like growth factor II.

Effect of zinc on strength and fatigue resistance of amalgam

OBJECTIVES

This study was conducted to determine the effect of zinc in amalgam on the static mechanical properties and resistance to fatigue-crack propagation of amalgams.

METHODS

Fatigue, creep, compressive and flexure tests were performed on high-Cu Dispersalloy (Johnson and Johnson Dental Products Co., East Windsor, NJ, USA) and low-Cu Velvalloy (S.S. White Dental Products Int., Philadelphia, PA, USA) in both Zn-containing and Zn-free formulations. Linear Elastic Fracture Mechanics principles were used to characterize the fatigue behavior (crack lengths were monitored).

RESULTS

The incorporation of Zn into these amalgams significantly improved their fatigue and creep resistance, while the effect of Zn on the static compressive and flexure strengths was not consistent. Zn significantly increased (p < 0.05) the resistance to fatigue crack propagation during Stage II crack growth for both amalgams, and increased the variations in crack velocity for a given stress intensity difference, without visibly altering the path or nature of the fatigue cracks. Possible influences on fatigue behavior were the mixed microstructure (particles and matrix), the nature of the crack tip, and creep.

SIGNIFICANCE

The superior resistance to tensile fatigue crack propagation of amalgams containing small amounts of Zn (approximately 1 wt%) in vitro compared with amalgams with no Zn correlated with the superior resistance to marginal breakdown in vivo of Zn-containing amalgams. The range of stress intensities over which stable cracks could propagate was small, while the large variations observed in fatigue crack growth rates for individual materials invalidate predicting a unique fatigue life from the empirical equations obtained.

Molecular cloning of an Actinobacillus pleuropneumoniae outer membrane lipoprotein (OmlA) from serotype 5a

The gene encoding an outer membrane lipoprotein (OmIA) was cloned from Actinobacillus pleuropneumoniae strain NG-8 (serotype 5a). The deduced amino acid sequence of OmIA from strain NG-8 showed 61% identity to the OmIA from serotype 1 strain, which confers protective immunity to pigs. Southern blot analysis showed the presence of a sequence highly homologous to the omIA gene of strain NG-8 in strains of serotype 5a, 5b and 10. A specific serum against OmIA of NG-8 also detected a homologous protein in the strains of these serotypes. These data shows the presence of antigenic variability among A. pleuropneumoniae OmIA proteins.

[A case of miliary tuberculosis with high-grade fever that remitted without antituberculosis therapy]

A 23-year-old man was admitted with a persistent high-grade fever of 20 days duration. Chest roentgenogram showed diffuse miliary shadows in both lung fields, highly suggestive of miliary tuberculosis. Sputum, gastric juice, and bronchoalveolar lavage fluid did not, however, reveal acid-fast bacilli on smears. A bone marrow aspirate and a transbronchial lung biopsy were also negative for caseating granulomas and tubercule bacilli. After admission, the high-grade fever remitted in several days without continuous antibiotic, antituberculosis or antipyretic therapy. Levels of inflammatory markers (CRP, ESR, alpha 2-globulin dropped simultaneously. Despite the atypical clinical course, miliary tuberculosis was suspected. We therefore carried out an open lung biopsy. The presence of caseating granulomas and acid-fast bacilli confirmed the diagnosis of miliary tuberculosis. The remission of miliary tuberculosis without treatment is very rare and the details of this case are presented herein with a discussion of the pertinent literature.

Sensitization to cockroach allergens of asthma patients in Japan

To evaluate the role of allergens from Periplaneta fuliginosa, which is the most predominant cockroach species in homes in Tokyo areas, for asthma sensitization, we measured specific IgE antibodies to two cockroaches, P. fuliginosa and Blattella germanica, and to a mite, Dermatophagoides farinae, in 171 sera from children with asthma by Pharmacia's CAP system. We found that 16% of the sera had anti-P. fuliginosa IgE, whereas 9.9% had anti-B. germanica and 85% anti-D. farinae IgE. Further, we measured the levels of Per f I (Per a I equivalent) allergen in the house dust from living room, kitchen and bedding. We detected the allergen in eight of ten homes. The Per a I equivalent levels in kitchen were higher than in other sites, but they were much lower than Der I and Der II as Dermatophagoides allergens.

Reduced mercury vapor release from dental amalgams prepared with binary Hg-in liquid alloys

For the past ten years, the amounts of mercury vapor released from dental amalgams and the possibility of side-effects caused by these amounts have been discussed. Although no adverse health effects have been substantiated from these minute amounts, besides rare cases of allergies, this release should be reduced. The aim of this study was to reduce the mercury evaporation from a high-copper amalgam during setting by triturating the alloy powder with binary Hg-In liquid alloys having various indium concentrations set at 0, 5, 10, 20, 30, 40, and 50 wt%. Specimens (n = 4) were made for each amalgam according to ANSI/ADA Specification #1 and placed into a measuring chamber kept at 36.5 +/- 0.5 degrees C, through which a continuous air flow of 0.75 L/min was pumped. The total mercury release was measured during the setting period, according to the method described by Ferracane et al. (1992). Four additional specimens were prepared from a modified 14% Indisperse amalgam powder for the purpose of comparison. The results showed that the release of mercury vapor decreased with increasing indium concentrations, and that the amalgams made with the Hg-In liquid alloy with 10% In or more released significantly less mercury than the modified 14% Indisperse. The method of mixing indium in mercury prior to trituration appeared to be another effective method for reducing mercury evaporation during setting. The reduced mercury release may be explained by a reduction of mercury concentration in the structure, a reduction of vapor pressure for the mercury in the matrix phases, or more efficient formation of a surface oxide layer.

Purification of a cell growth factor from a human lung cancer cell line: its relationship with ferritin

We have purified a cell growth factor from a human lung cancer cell line, T3M-30, which was established in a protein-free chemically defined medium. The factor, designated carcinoma-derived growth factor (CD-GF), stimulated proliferation of a variety of cells, including human leukemia cells, HL-60, and melanoma cells, SK-28. Half-maximum stimulation by the purified CD-GF was achieved at a concentration of 40 ng/ml. In the purified CD-GF, two major protein bands of 24 kDa and 22 kDa were identified on a SDS polyacrylamide gel. The partial amino acid sequences of the 24 kDa protein were determined from two peptide fragments obtained by V8 protease treatment. The partial sequences were identical to those of heavy chain of human ferritin. The activity of the purified CD-GF was coprecipitated completely with a monoclonal antibody to heavy chain of ferritin. Ferritin has been considered to inhibit cell growth. However, human heart ferritin was capable of stimulating the growth of HL-60 cells. These results suggest that CD-GF is related to ferritin and ferritin is a growth factor of HL-60 leukemia cells.

Correlation of cytotoxicity with element release from mercury- and gallium-based dental alloys in vitro

OBJECTIVES

An in vitro screening test was used to compare the cytotoxicity and elemental release from mercury- and gallium-based dental restorative materials.

METHODS

The test employed three sequential extractions of the samples into cell-culture medium which were then used to evaluate the cytotoxicity of the samples and the release of elements from the samples. Cytotoxicity was measured by placing the extract in contact with Balb/c mouse fibroblasts for 24 h and measuring the succinic dehydrogenase activity of the cells. The release of elements was measured by means of atomic absorption spectrophotometry.

RESULTS

Samples of Tytin (Kerr) showed no cytotoxicity compared to Teflon controls. Dispersalloy (Johnson and Johnson) was severely cytotoxic initially when Zn release was greatest, but was less toxic between 48 and 72 h as Zn release decreased. Gallium Alloy GF (Tokuriki Honten) was moderately cytotoxic after 8 h, and increased in cytotoxicity thereafter, which correlated with a substantial and persistent release of Ga from this material.

SIGNIFICANCE

The results of the current study concurred with in vivo assessments of these materials, and the use of sequential extractions was useful in determining trends in the cytotoxicity and elemental release from these materials.

A cyclin-dependent kinase inhibitor, butyrolactone I, inhibits phosphorylation of RB protein and cell cycle progression

Butyrolactone I is a selective inhibitor of the cyclin-dependent kinase (cdk) family. It inhibits both cdk2 and cdc2 kinase, but scarcely affects C-kinase, A-kinase, casein kinases, MAP kinase or EGF receptor-tyrosine kinase (Kitagawa et al., 1993, Oncogene, 8, 2425-2432). We studied the effects of butyrolactone I on the cell cycle as well as on phosphorylation of retinoblastoma protein (pRB). Butyrolactone I inhibited phosphorylation of pRB catalyzed by cyclin A-cdk2 produced by baculovirus in vitro. Furthermore, it inhibited phosphorylation of pRB and cell cycle progression from G1 to S phase in WI38 cell cultures. WI38 cells arrested at the G0 phase by serum starvation progressed in the cell cycle after serum stimulation. pRB was phosphorylated after 10 h serum stimulation. Incorporation of [3H]thymidine into the cells began to increase after 16 h serum stimulation. These processes were inhibited by butyrolactone I. Flow cytometric analysis showed that exposure to butyrolactone I inhibited progression of the cell cycle from G1 to S phase. These data suggested that initiation of DNA synthesis was inhibited by butyrolactone I and that the cell cycle was arrested in the G1 phase. Butyrolactone I also inhibited H1 histone phosphorylation in human WI38 cells and their G2/M progression. tsFT210 cells, a temperature-sensitive cdc2 mutant cell line, were synchronized at G2/M at a nonpermissive temperature, butyrolactone I inhibited the cell cycle progression of these cells at G2/M at the permissive temperature. Thus butyrolactone I, a cyclin-dependent kinase family inhibitor, which prevented the phosphorylations of the cell cycle-regulating proteins pRB and H1 histone, inhibited the cell cycle at G1/S and G2/M, respectively. These results suggest that the phosphorylations of pRB and H1 histone may play crucial roles in G1/S and G2/M progression, respectively, although it is possible that phosphorylations of other proteins by cdks are involved in G1/S and G2/M progression.

Quick-freeze, deep-etch visualization of exocytosis in anterior pituitary secretory cells: localization and possible roles of actin and annexin II

The exocytotic process in the anterior pituitary secretory cells was studied using quick-freeze deep-etch electron microscopy, fluorescein-isothiocyanate-phalloidin staining, heavy meromyosin decoration, and immuno-electron microscopy. The subcortical actin filaments are distributed unevenly in the peripheral cytoplasm. Few secretory granules are seen beneath the plasma membrane in the region where the peripheral cytoplasm is occupied by numerous subcortical actin filaments. On the contrary, in the region free of the subcortical actin filaments, many secretory granules lie in contact with the plasma membrane. Thus, the subcortical actin filaments may control the approach of the secretory granules to the plasma membrane in these cells. The granule and plasma membranes that lie in close proximity are linked by intervening strands. Unfused portions of both membranes remain linked by these strands during membrane fusion and opening. These strands may be involved in membrane contact, fusion and opening during exocytosis. Annexin II (calpactin I) has been demonstrated immunocytochemically to be localized at the contact sites between the granule and plasma membranes, and is therefore a possible component of the intervening strands. Membrane fusion starts within focal regions of both membranes less than 50 nm in diameter. The plasma membrane shows inward depressions toward the underlying granules immediately before fusion. The disappearance of intramembranous particles from the exocytotic site of the membrane has not been observed.

Single amino acid substitution (840Arg-->His) in the hormone-binding domain of the androgen receptor leads to incomplete androgen insensitivity syndrome associated with a thermolabile androgen receptor

We have characterized the androgen receptor in a Japanese girl and her maternal cousin in a family with incomplete androgen insensitivity syndrome, and have investigated the molecular basis. Whole-cell androgen binding assay in cultured genital skin fibroblasts from both patients showed a normal maximum binding capacity and a normal apparent dissociation constant. However, androgen binding in fibroblasts from both patients decreased to 30% when the assay temperature was raised from 30 degrees C to 41 degrees C, indicating the presence of the thermolability of ligand binding to the androgen receptor. Sequence analysis of the coding exons of the androgen receptor gene from the patients revealed a single nucleotide substitution at position 2881 in exon G, resulting in the conversion of arginine (CGT) to histidine (CAT) at amino acid position 840 in the hormone-binding domain of the androgen receptor. The family study showed that the mothers and the maternal grandmother of the patients are heterozygous carriers for this mutation, whereas the father does not carry it, supporting the view that androgen insensitivity syndrome is an X chromosome-linked disorder. The single amino acid substitution may explain the qualitative abnormality of the androgen receptor displaying thermolability, which is thought to be the pathogenesis of incomplete androgen insensitivity syndrome in the patients.

[Origin and cytogenetic abnormalities of sarcoid epithelioid cells]

The sarcoid epithelioid cells are believed to be a variant of tissue macrophages, which derived from circulating monocytes in blood. Formation of monocytes and macrophages are controlled by hematopoietic growth factors, i.e; colony-stimulating factors in the bone marrow. In the presence of colony-stimulating factors and/or vitamin D3, blood monocytes can proliferate and differentiate into epithelioid cells and multinucleated giant cells. In view of the evidences that sarcoid granulomas produce colony-stimulating factors and active form of vitamin D3, these results suggest that active metabolites of vitamin D3 and colony-stimulating factors produced by sarcoid epithelioid cells, induces the differentiation and proliferation of circulating monocytes into macrophage-epithelioid cells, which in turn form sarcoid granulomas. Since sarcoidosis is a disorder of cell proliferation and differentiation, a question has been always kept in my mind whether the sarcoid granulomas are chronic inflammation per se or neoplastic in nature. Interestingly, cytogenetic studies revealed that most of the epithelioid cells were aneuploid; the chromosomal number ranged from the near-haploid to the near diploid number. In addition, The distribution of DNA content of the granuloma cells was fairly wide. Our observations raise a question whether the aneuploidy in sarcoid granulomas may be due to viral infection or exposure to carcinogens as in the case of neoplastic cells. It is also possible to speculate that the aneuploidy may be a mechanism of macrophage differentiation similar to immunoglobulin gene rearrangement in B lymphocytes. Further studies are required.(ABSTRACT TRUNCATED AT 250 WORDS)

Hospital-wide PACS with a digital image intensifier TV system

Tokyo Hitachi Hospital, Hitachi Ltd., has used a hospital-wide PACS for over 1 year. The system runs a 100 Mb/s optical fiber network over the whole hospital including wards and outpatient clinic rooms, with 11 image workstations. The network links digital imaging modalities such as X-CT, MRI, computed radiography (CR) and digital radiography (DR) with a 2048 x 2048 (2k x 2k) matrix image intensifier television (I.I.-TV) system. These modalities generate about 200 images/day. The system has managed over 300,000 images of about 8000 patients so far. Although being still under improvement, the system has really been used for routine work. The hospital-wide PACS of a small hospital has been proved to be very useful for both image diagnosis and image management.

[A Japanese pedigree with oculopharyngeal muscular dystrophy]

We investigated a Japanese pedigree with oculopharyngeal muscular dystrophy (OPMD) which included the probands of two sisters and a brother. Case 1 (Fig. 1): A woman born in 1940 at Fuji City, Shizuoka prefecture (Pacific coast side, which located about 80 miles west from Tokyo) was insidiously suffering from dysphagia and eye lid ptosis since her age of 40. She was admitted to Shizuoka Red Cross Hospital when 48 years old, because of difficulty of going upstairs. Neurological examination revealed severe eye lid ptosis without eye movement disorders, dysphagia, and moderate weakness on neck and proximal muscles of extremities without definite atrophy and fasciculation. In the laboratory data, serum creatine kinase level was slightly elevated to 215 U/l. Electromyographic findings showed myogenic pattern on the extremities but no evidence of the existence of myasthenia gravis and neurogenic involvement. Intranuclear tubular filaments were found in 3% of muscle fibers from her left biceps muscle. Case 2: The elder sister of the case 1 was suffering from eye lid ptosis without eye movement disorder and severe dysphagia since the age of 44. Case 3: The younger brother of the case 1 was suffering from dysphagia and proximal muscle weakness since the age of 40. We found eye lid ptosis, dysphagia and/or proximal muscle weakness in 24 cases (men: 12 cases, women: 12 cases) out of 50 examined members of this pedigree after their ages of 40 (Fig.3; family tree). It was concluded that this pedigree had cases of oculopharyngeal muscular dystrophy with autosomal dominant inheritance which was quite rare in Japanese.

Reduction in operatory mercury levels after contamination or amalgam removal

The threshold limit value (TLV) for occupational exposure to mercury can be exceeded in the dental operatory after a contamination event or during certain dental procedures. The objective of this study was to determine the time required for the mercury vapor levels to return to baseline in both non-ventilated and ventilated operatories after they had been contaminated with mercury to the TLV of 0.050 mg/m3; and to evaluate the efficiency of an activated charcoal filtering device for removing mercury vapor. The results showed that even in a poorly ventilated operatory, the mercury vapor level returned to background within 20-30 minutes after a contamination, and within 10-20 minutes when the operatory was ventilated. The filtering device reduced the level of mercury vapor by approximately 25% during a continuous contamination event, but did not clear the operatory faster than normal settling after a limited source contamination. The filter caused a significant reduction in mercury in the breathing zones of the patient and dentist during and after amalgam removal, but did not eliminate the exposure. This study demonstrated the difficulty in contaminating an operatory with mercury vapor and confirmed the limited time mercury remains airborne, presumably due to its density and affinity for surfaces.

[The usefulness of the bayesian method for the prediction of plasma theophylline levels in asthmatic children during RTC therapy by the sustained preparation of theophylline]

Pharmacokinetic prediction of plasma theophylline levels during RTC therapy by the sustained release preparation of theophylline was studied with a one compartment model in children aged 1-6 years old showing comparatively long sleeping time. Using the parameters measured from the population of 1-17 year olds, the accuracy of the prediction was studied by the Bayesian method. Absolute error (A.E.) and estimation error (E.E.) were about 2.0. The prediction values of E.E. seemed to be rather higher if the measured values of the absorption phase were used, and the values seemed to be rather lower if the values of the elimination phase were used. From these results it might be concluded that the Bayesian method seems to be useful for RTC therapy in children under 6 years old.

Tetanus toxin and Clostridium perfringens enterotoxin as tools for the study of exocytosis

The role of calmodulin in exocytotic secretion was studied using digitonin-permeabilized bovine adrenal chromaffin cells to examine the effect of calmodulin directly introduced into the cells and using tetanus toxin as a specific inhibitor of exocytotic secretion. Addition of calmodulin to the permeabilized cells increased Ca(2+)-dependent norepinephrine release in a dose-dependent manner. The enhancement of release by calmodulin was specific to calmodulin: bovine serum albumin, actin, and caldesmon had no such effect. Enhancement of release by calmodulin occurred at Ca2+ concentrations of more than 10(-6) M and increased with an increase of Mg2+ concentration. The release of norepinephrine enhanced by calmodulin was inhibited by tetanus toxin. These results indicate directly that calmodulin plays an important role in exocytotic secretion from chromaffin cells. Exocytosis is known to occur by fusion of plasma membrane with limiting membranes of secretory vesicles following an increase in intracellular Ca2+. We used the enterotoxin of Clostridium perfringens type A as a specific tool to modify plasma membrane permeability to induce calcium influx. Multigranular exocytosis was recognized electron-microscopically in addition to the single-granular exocytosis in rat anterior pituitary cells and pancreatic acinar cells treated with the enterotoxin in the presence of extracellular Ca2+. The treatment with the enterotoxin did not induce any drastic change in the fine membrane structures of both types of cells. The enterotoxin-treated anterior pituitary cells and pancreatic acinar cells should provide a useful system for studying the molecular mechanism of fusion of membranes in exocytosis.

BE-23372M, a novel protein tyrosine kinase inhibitor. II. Physico-chemical properties and structure elucidation

BE-23372M, a new protein tyrosine kinase inhibitor, has been obtained as a reddish orange solid. The compound, C17H12O6, HRFAB-MS: m/z 312.0625 (M)+, is an acidic substance, showing UV (MeOH) lambda max (epsilon) 266 (8,800), 426 nm (20,400), and IR (KBr)vmax 1752(C = O) and 3298(OH) cm-1. The structure of BE-23372M, (E)-3-(3,4-dihydroxybenzylidene)-5-(3,4-dihydroxyphenyl)-2(3H)-fur anone, has been elucidated by 1H and 13C NMR studies.

BE-23372M, a novel protein tyrosine kinase inhibitor. III. Synthesis

In a preceding paper, the physico-chemical properties and structural elucidation of BE-23372M, a potent novel protein tyrosine kinase inhibitor, were described. In this paper, we report the synthesis of BE-23372M from 3-(3,4-dimethoxybenzoyl)propionic acid and veratraldehyde or 3,4-diacetoxy-benzaldehyde. The structure of BE-23372M was confirmed to be (E)-3-(3,4-dihydroxybenzylidene)-5-(3,4-dihydroxyphenyl)-2(3H)-fur anone.

BE-23372M, a novel protein tyrosine kinase inhibitor. I. Producing organism, fermentation, isolation and biological activities

BE-23372M, a novel protein tyrosine kinase inhibitor, was isolated from the culture broth of a fungus. The producing strain, F23372, was identified as Rhizoctonia solani, based on the cultural and morphological characteristics. The active principle was extracted from the mycelium with acetone and purified by solvent extraction, silica gel column chromatography and Sephadex LH-20 column chromatography. BE-23372M showed strong inhibitory activity against EGF receptor kinase with IC50 values of 0.02 and 0.03 microM on two different substrates, whereas IC50 values against protein kinase C and cAMP-dependent protein kinase were 4.5 and > 20 microM, respectively. The compound inhibited the growth of A431 human epidermoid carcinoma and MKN-7 human stomach cancer cell lines with IC50 values of 8 and 24 microM, respectively.

Purification and characterization of endothelin-1 degradation activity from porcine kidney

In order to identify the membrane-bound peptidase that is responsible for the degradation of endothelin (ET), an endothelin-1 (ET-1) degradation enzyme was solubilized from membrane fractions of porcine kidney with 1% Triton X-100, and subsequently purified by column chromatographies, i.e., diethylamino-Sepharose ion exchange, gel permeation, Con A Sepharose and hydroxyapatite chromatography. On DEAE-Toyopearl ion exchange column chromatography, the ET degradation enzyme and aminopeptidase were separated, but ET degradation enkephalinase activities were not separable. In order to separate ET degradation enzyme and enkephalinase, the active fractions were loaded on each of the column chromatographies: sephacryl S-200, Con A Sepharose or hydroxyapatite. The ET degradation activities were co-migrated with enkephalinase activities on all of the three chromatographies. In addition, the ET degradation activities were inhibited by thiorphan, phosphoramidon and EDTA, which are known to inhibit enkephalinase. These results suggest that ET degradation activity in the membrane fractions of the kidney is related to enkephalinase and may be involved in the degradation of ET-1 in vivo.

BE-23372M, a novel and specific inhibitor for epidermal growth factor receptor kinase

The fungal metabolite BE-23372M is a structurally novel protein kinase inhibitor. Its IC50 for epidermal growth factor (EGF) receptor kinase was 0.03 microM. IC50 values of BE-23372M for other protein tyrosine kinases, erbB-2, p43v-abl, insulin receptor kinase, and p60c-src were 0.42, 1.0, 3.3, and 4.5 microM, respectively, and the IC50 for protein kinase C, a serine/threonine kinase, was 4.1 microM. Cdc2 kinase, casein kinases I and II and cAMP-dependent protein kinase were not inhibited by 20 microM BE-23372M. A kinetic study showed that BE-23372M was competitive with respect to the substrate peptide and to ATP. Autophosphorylation of solubilized EGF receptor kinase was clearly inhibited by 0.1 microM BE-23372M. Autophosphorylation of EGF receptor in A431 cells was also inhibited. These results show that BE-23372M is a potent and specific EGF receptor kinase inhibitor. It should be a valuable tool for EGF receptor kinase research.

Digestion of endothelin-1 on cultured vascular smooth muscle cells

The degradation of 125I-endothelin-1 (125I-ET-1) was examined on cultured porcine aortic endothelial cell (EC) and rat vascular smooth muscle cell (SMC) by HPLC analysis. The degradation of ET-1 was observed on SMC and was slightly observed on EC. Membrane fractions of SMC had a strong potency for the degradation of ET-1 and retained activity even in plasma. This activity was inhibited with some of the noble inhibitors which were known as enkephalinase inhibitors. These results suggest that endothelin degradation enzyme on SMC is related to enkephalinase and that this enzyme plays a significant role in the degradation of ET-1 in vivo.