Isolation and characterization of tannin-degrading bacteria from the rumen of wild Hokkaido sika deer (Cervus nippon yezoensis)

We isolated tannin-degrading bacteria from the rumen of wild Hokkaido sika deer and characterized their phylogeny and tannase activity in relation to sample sources. The condensed tannin level was higher in all deer rumen samples (n = 20) than in forage-fed cattle rumen samples (n = 6), whereas no hydrolyzable tannins were detected in any of the rumen samples. Rumen bacteria were enumerated on nonselective brain heart infusion (BHI) agar medium and then transferred onto tannic acid-containing BHI agar plates to screen for bacteria only showing growth (tannin-resistant bacteria) and those showing both growth and a clear zone (tannin-degrading bacteria). Summer samples provided only tannin-resistant bacteria, none of which showed tannin-degrading activity. Although winter samples also provided tannin-resistant bacteria, most isolates exhibited tannin-degrading activity. A total of 70 isolates exhibiting tannin-degrading activity were classified as Streptococcus bovis group based on 16S rRNA gene sequencing and further classified into two groups, either group A or group B. Group A consisted of isolates showing weak tannase activity, whereas group B included a majority of the isolates exhibiting high tannase activity. These results suggest that wild Hokkaido sika deer develop tannin-degrading Streptococcus in the rumen during winter, which allows access to woody food materials rich in tannins.

Seasonal differences in rumen bacterial flora of wild Hokkaido sika deer and partial characterization of an unknown bacterial group possibly involved in fiber digestion in winter

Rumen digesta was obtained from wild Hokkaido sika deer to compare bacterial flora between summer and winter. Bacterial flora was characterized with molecular-based approaches and enrichment cultivation. Bacteroidetes was shown as a major phylum followed by Firmicutes, with similar proportions in both seasons. However, two phylogenetically unique groups in Bacteroidetes were found in each season: unknown group A in winter and unknown group B in summer. The ruminal abundance of unknown group A was the highest followed by Ruminococcus flavefaciens in winter. Moreover, the abundance of these two was higher in winter than in summer. In contrast, the abundance of unknown group B was higher in summer than in winter. In addition, this group showed the highest abundance in summer among the bacteria quantified. Unknown group A was successfully enriched by cultivating with oak bark and sterilized rumen fluid, particularly that from deer. Bacteria of this group were distributed in association with the solid rather than the liquid rumen fraction, and were detected as small cocci. Accordingly, unknown group A is assumed to be involved in degradation of fibrous materials. These results suggest that wild Hokkaido sika deer develop a rumen bacterial flora in response to changes in dietary conditions.

Abstract P1-07-23: The quality and quantity of visceral fat tissue are associated with insulin resistance and survival outcome after chemotherapy for patients with early-stage breast cancer

Background: Obesity and insulin resistance are associated with inferior levels of chemosensitivity and overall prognosis for breast cancer (BC) treatment. Recent studies suggest that the quality and quantity of visceral adipose tissue (VAT) play a significant role in adipocyte function, and are related to insulin resistance. We therefore tested the hypothesis that high amount and low quality of VAT worsen treatment outcomes via insulin resistance mechanisms.

Patients and Methods: We examined two independent studies: a cross-sectional study (cohort 1) and a retrospective study (cohort 2). Cohort 1 included 106 women with early-stage BC who were undergoing surgery. Patients with normal weight (17.5< body mass index [BMI, kg/m2] ≤25, n = 53) and overweight/obese patients (BMI >25, n = 53) were selected by a pair-matching method. Insulin resistance was evaluated by HOMA-R: fasting insulin (microU/L) × fasting glucose (nmol/L)/22.5. And insulin-like growth factor (IGF) family including IGF-1 and IGF-binding protein 3 (IGFBP3) were measured before beginning treatment. The amounts of visceral fat (aVAT) was measured by 3-dimensional volumetric software using the stocked computed tomography (CT) imaging data. The quality of VAT was assessed based on the mode value of CT Hounsfield Unit of VAT (VAT-HU) at navel level of CT axial view. The association between the former variables and the quality and quantity of VAT was analyzed. Cohort 2 included 271 patients who received chemotherapy in the neo-adjuvant (NAC) or adjuvant setting. Imaging analysis was performed in the same way, and the association between those values and survival outcome after chemotherapy was analyzed by retrospective chart review.

Results: In cohort 1, aVAT was significantly correlated with serum insulin and HOMA-R levels (Pearson's R 0.44 and 0.42, respectively; P<0.05). On comparing the two groups divided by BMI, the levels of IGF-1 and IGFBP3 were not significantly different between the normal weight and the overweight/obese groups (P = 0.31 and 0.77, respectively). However, the overweight/obese group demonstrated significantly higher HOMA-R (P<0.05). In cohort 2, aVAT was significantly correlated with BMI (P<0.05). In a multivariate analysis, pathological complete responses were not associated with aVAT (P = 0.60). After a median follow-up of 112 months, tertile stratification revealed that the third tertile of aVAT had a significantly shorter distant disease free survival (DDFS) in the NAC setting (p<0.05). When adjusted by covariates in the Cox proportional regression model, aVAT and VAT-HU demonstrated significant contribution to a worsened DDFS ([p<0.05, hazard ratio {HR} 1.39; 95% confidence interval {CI} 1.11 to 1.75] and [p<0.05, HR 1.20, 95% CI 1.01 to 1.43], respectively).

Conclusions: Our study found that high amounts and low quality of VAT worsen treatment outcomes. Furthermore, we found that insulin resistance was related to those two factors. Although further validation is needed, our present work suggests the importance of evaluating the quality and quantity of visceral fat for estimating insulin resistance and treatment outcomes after chemotherapy for patients with early-stage BC.

Citation Format: Iwase T, Sangai T, Nagashima T, Sakakibara M, Fujimoto H, Sawabe Y, Nagashima K, Otsuka M. The quality and quantity of visceral fat tissue are associated with insulin resistance and survival outcome after chemotherapy for patients with early-stage breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-07-23.

Corticotroph cell adenoma without typical manifestations of Cushing's disease presenting with cavernous sinus syndrome following pituitary apoplexy

This report presents a unique case of corticotroph cell adenoma in a 30-year-old man without acromegaly or features typical of Cushing's disease, who developed cavernous sinus syndrome following pituitary apoplexy. Magnetic resonance imaging revealed a large intrasellar/suprasellar mass with pituitary hemorrhage and extension of a hematoma to the anterior base of the skull. Urgent transnasal pituitary surgery revealed an acidophilic pituitary adenoma, with immunoreactivity for ACTH and GH and expression of proopiomelanocortin (POMC) and GH messenger ribonucleic acid (mRNA) demonstrated by in situ hybridization. To our knowledge, a silent corticotroph cell adenoma with GH production has never been reported. This type of adenoma may potentially enlarge and develop tumoral hemorrhage because it is free of endocrinological symptoms.

Neuropsychological changes after surgery for anterior communicating artery aneurysm

Neuropsychological disturbances following surgery for anterior communicating artery aneurysms were analyzed in 26 patients (11 males, 15 females) using the Hasegawa dementia scale-revised (HDS-R) over a 3-year period. The patients were aged from 34 to 76 years (mean 54.1 years). Lesions in the frontal lobe were evaluated using computed tomography (CT). Twenty-three patients had symptoms over the course. Four patients had basal forebrain lesion, five had ventral frontal lesion, and 12 had no lesion. Patients with basal forebrain lesion and no lesion tended to show disorientation. The mean HDS-R score was 10.2 points in the patients with ventral frontal lesion, and 13.5 points in the patients with no lesion. These scores are within the range for dementia. The mean HDS-R score in patients with basal forebrain and striate lesions was over 25 points and beyond the range for dementia. Significant differences were observed in the HDS-R score between patients with ventral frontal lesion and basal forebrain lesion, and between patients with no lesion and basal forebrain lesion (p < 0.05). Recovery from neuropsychological disturbances was poorer in patients with ventral frontal lesion and no lesion compared to those with basal forebrain and striate lesions, and their symptoms tended to persist.

Acute subdural hematoma due to near-drowning--case report

A 46-year-old male was transferred to our hospital after near-drowning when swimming. Examination found no subcutaneous hematoma or abrasion on his head. Cardiopulmonary resuscitation was started immediately. Emergent computed tomography (CT) revealed no abnormalities. The next day, his consciousness level improved and repeat CT suggested an acute spontaneous subdural hematoma in the parieto-occipital region. The acute subdural hematoma was evacuated. The source of bleeding was probably an abnormally large vein located in the center of the hematoma. The patient was discharged without neurological deficit. Repeat CT is needed even if there were no abnormality on initial CT after drowning.

[Inhibitory effects of natural medicines on the enzymes related to the skin]

In this paper, we investigated the inhibitory effects of water extracts from sixty-six natural medicines on the enzymes related to the skin, which were tyrosinase, hyaluronidase and collagenase. To clarify the inhibitory components in water extracts, tannin quantity and the inhibitory activity of the water extracts after removal of phenolic compounds using polyclar AT, were measured. Twelve kinds of natural medicines were found to have tyrosinase inhibitory activity. Six of them showed that tannin, which contains sufficient amounts in extracts, might be major inhibitory compounds due to a significant decrease of inhibition by these samples after removal of phenolic compounds. The inhibitory compound of Aurantii fructus immaturus was thought phenolic compounds except tannin. The inhibitory compounds may include Armeniacae semen, Perillae folium and Persicae semen besides a phenolic compound. Twenty-seven species among the natural medicines studied showed inhibitory activity on hyaluronidase. Phenolic compounds in these extracts except Artemisiae argyi folium, could not be candidates for hyaluronidase inhibitors. Seven kinds of the natural medicines have inhibitory activity on collagenase. It was estimated that these inhibitory compounds were phenolic compounds. These results are to be expected for finding novel compounds for skin disease or skin-care cosmetics.

[Clear cell ependymoma--a case report]

A case of intraaxial clear cell ependymoma is reported. A 46-year-old man complained of right hemiparesis. CT scan showed a mass lesion on the median plane with a huge cyst in the left frontal lobe. MRI showed an iso-low intensity mass by T1-weighted image. The tumor was heterogeneously enhanced by Gd-DTPA and the wall was enhanced as well. Angiogram revealed a tumor stain from the right internal carotid artery. The main mass of the tumor was totally removed but the cystic wall was left removed. Histopathological examination revealed clear cell ependymoma. Immunohistochemical examination revealed that, although vimentin and NSE were positive, GFAP, synaptophysin and S-100 were negative. Ultrastructual examination revealed cilia, microvilli and desmosomal junctions. The patient fully recovered after operation and showed no sign of recurrence after an year of follow-up. Clear cell ependymoma is a rare variant of ependymoma. Ultrastructual examination was more useful than immunohistochemical examination for diagnosis.

Epidural hematoma of the clivus. Case report

This 8-year-old boy presented with a rare case of epidural hematoma of the clivus and atlantoaxial dislocation caused by a hyperflexion injury sustained in a traffic accident. Magnetic resonance (MR) imaging demonstrated an epidural hematoma in the posterior fossa that compressed the pons and medulla. On admission, the patient was confused and had bilateral abducens palsy. He was treated conservatively, and 6 months after admission, the epidural hematoma on the clivus had disappeared on MR imaging and the bilateral abducens palsy was cured. Only two such cases have been reported in the literature. In this report, the authors discuss the mechanism of hematoma formation in this region of the brain.

Changes in levels of serum erythropoietin, serum iron and unsaturated iron binding capacity during chemotherapy for lung cancer

BACKGROUND

The serum erythropoietin level increases markedly during chemotherapy for leukemia. A number of hypotheses have been built for the mechanism, none of them satisfactory. Difficulty in evaluating bone marrow activity hampers the elucidation. Therefore, we focused on patients who had non-hematological cancer and no evidence of bone marrow suppression.

METHODS

Twelve patients, who had lung cancer (four with small cell cancer and eight with non-small cell cancer) and who had not undergone any chemotherapy, were studied. During chemotherapy, we measured serum erythropoietin, serum iron, unsaturated iron binding capacity and hemoglobin concentration in these patients.

RESULTS

The serum erythropoietin level before chemotherapy (10.8 +/- 7.4 mU/ml) was within the normal range but the peak values after the first treatment (73.4 +/- 90.4 mU/ml) increased in all patients. In the patients with small cell cancer, a transient but marked increase in erythropoietin value (204.6 +/- 167.3 mU/ml) was observed after each session of chemotherapy while hemoglobin concentration decreased gradually. Throughout treatments, elevation of the serum iron concentration and concomitant reduction of unsaturated iron binding capacity were observed after each session of chemotherapy. They regained their original values whilst the serum erythropoietin level decreased after each chemotherapy session was completed.

CONCLUSIONS

It is suggested that the suppression of erythroid marrow by chemotherapeutic agents causes the changes in serum erythropoietin level during chemotherapy in patients with lung cancer.

Morphometric nerve fiber analysis and aging process of the human abducent nerve

Myelinated nerve fibers of the human abducent nerve were analyzed with a new staining method that permits simultaneous observation of the axon and surrounding myelin sheath. The following equipment was employed for the measurements: an image-analyzing digitizer, a microscope equipped with a drawing tube (or camera lucida), and a computer for data storage and statistical analysis. The numbers, transverse areas, and circularity ratios of axons were measured in 10 human abducent nerves. The average number was 1,997 with a definite decrease with age, and the average area was 3.90 micron 2.

Unmyelinated nerve fiber analysis of the human abducent nerve

Unmyelinated nerve fibers of the abducent nerve have occasionally been observed with electron microscopes, but, to our knowledge, they have never been evaluated from the morphometric point of view. We analyzed the aging process of the unmyelinated nerve fibers in the human abducent nerve with the help of a new staining method suitable for morphometric research on the nervous system. We studied numbers and transverse areas of unmyelinated fibers of the abducent nerve in 10 cadavers. Our findings were that (1) these fibers were distributed diffusely, (2) their number decreased with age, and (3) the mean transverse area did not change with age. Most of the unmyelinated axons were thinner than the myelinated axons. These results may be important for analysis of clinical signs in relation to aging and ophthalmologic functions.

Polysaccharide of Astragali radix enhances IgM antibody production in aged mice

The effect of Astragali Radix (AR) on IgM antibody production in mice of various ages (10 weeks, 36 weeks and 60 weeks) was examined. The antibody production levels in the 36- and 60-week-old mice were significantly decreased to about 70 and 60% of that in the 10-week-old mice. The enhancement effect of a crude polysaccharide AR fraction on the antibody production was nil in the 10-week-old mice, but significant enhancement effects were observed in the 36- and 60-week-old mice, compared to the age-matched control. Two polysaccharides active in the enhancement of the IgM antibody production in the aged mice were isolated from the high molecular weight fraction of AR by cetavlon precipitation, ion-exchange and gel permeation chromatography. The molecular masses of these polysaccharides were calculated by HPLC in salt solution. Only one major peak was observed for each, and their molecular masses were estimated to be 1.2 x 10(4) and 2.2 x 10(4). The major components of these polysaccharides were neutral carbohydrates (89.3 and 95.5%), followed by uronic acid and protein; glucose was the predominant sugar component.

[3 Cases of blunt chest trauma]

3 Cases of blunt chest trauma were reported, including aortic isthmus rupture, diaphragmatic injury and right main bronchial rupture. All cases were injured by traffic accidents. The first case was a 21-year-old man complicated with aortic injury and femoral bone fracture and died of intrapleural rupture before thoracotomy. The second case was a 49-year-old man who had right 11th rib fracture and he received emergent thoracotomy due to hemorrhagic shock. We found accidentally arterial massive bleeding by the diaphragmatic injury at thoracotomy and ligated directly. The third case was a 19-year-old man and he was unconscious on admission and rupture of the right main bronchus was found by bronchofiberscope and performed pneumectomy. One patient died and other two patients have survived. Blunt chest trauma sometimes lead to fatal damage of vital organs. So it is necessary to make early diagnosis and perform the emergent operations for life salvage.

In vitro chemosensitivity of human pancreatic cancer cell lines

CONCLUSION

These results show that eight pancreatic cancer cell lines are broadly sensitive to CDDP, and that chemotherapy for pancreatic cancer may improve the prognosis by more effective drug delivery to cancer cells.

BACKGROUND

Chemotherapy for pancreatic cancer does not satisfactorily improve prognosis. The efficacy of chemotherapy depends on choosing sensitive anticancer drugs.

METHODS

The in vitro chemosensitivity of eight human pancreatic cancer cell lines was investigated. Growth inhibition was measured by 3H-thymidine incorporation assays for doxorubicin hydrochloride (ADM), mitomycin C (MMC), cisplatin (CDDP), and etoposide (VP-16), and by Alamar Blue assay for (AB assay) 5-fluorouracil (5-FU). The cells were exposed to ADM, MMC, CDDP, and VP-16 for 2 h, and 5-FU for 72 h. From the dose-response curves, the 50% growth inhibition (IC50) level for each drug was estimated.

RESULTS

The IC50 after 2 h of exposure of each of the eight kinds of cell lines to each anticancer drug ranged from 0.12-8.2 micrograms/mL for ADM, 0.066-25 micrograms/mL for MMC, 0.57-7 micrograms/mL for CDDP, 0.68-300 micrograms/mL for VP-16. IC50 after 72 h of exposure to 5-FU ranged from 1.8-23 micrograms/mL.

Changes in serum erythropoietin and the reticulocyte count during chemotherapy for leukemias

We serially determined serum erythropoietin (Epo) and the reticulocyte count in patients with various types of leukemia during chemotherapy. Serum Epo increased soon after the initiation of chemotherapy and decreased after the termination of therapy irrespective of the types of leukemia or treatment regimen. However, it did not stay at low level but fluctuated. The reticulocyte count, on the other hand, showed a transient rise while serum Epo level descended. The value of serum Epo when increased was higher than the value expected from hemoglobin concentration; this finding was similar to that in aplastic anemia. These results suggest that myelosuppression is a major factor for the increase in serum Epo level during leukemia chemotherapy.

Serum erythropoietin measurements by a one-step sandwich enzyme linked immunosorbent assay in patients with hepatocellular carcinoma and liver cirrhosis

Erythrocytosis is occasionally observed in patients with hepatocellular carcinoma (HCC). The pathogenesis of the phenomenon remains uncertain. It has been speculated that tumors produce erythropoietin (Epo), and several studies on the Epo in tumor tissues have been reported. Using a sensitive enzyme linked immunosorbent assay, we measured the serum Epo concentration in 92 HCC patients and 30 liver cirrhosis (LC) patients. The levels of Epo in normal subjects, HCC patients and LC patients were 10.5 +/- 4.1 (mean +/- SD, mU/ml), 55.6 +/- 218.0 and 18.4 +/- 19.4, respectively. Some patients with high Epo values had low levels of hemoglobin (Hb), and a scatter-gram of the two parameters was similar to that in iron deficiency anemia. In patients whose Hb levels were more than 12 g/dl, we found Epo levels of 15.0 +/- 8.8 (mean +/- SD mU/ml) and 10.3 +/- 7.7 in HCC and LC, respectively. Epo values in HCC were significantly higher than those of normal subjects (P < 0.001) and LC patients (P < 0.05), and 18.2% (10/55) had concentrations above the upper limit of the normal range. The increase was not, however, a marked one. In conclusion, as the incidence of erythrocytosis was low (2.2%) in HCC patients, the high Epo values in some patients could be related to the abnormal production of Epo by HCC.

[Evaluation of a one step sandwich enzymeimmunoassay for serum erythropoietin--serum erythropoietin values in polycythemia vera and related hematological disorders]

We evaluated a newly developed enzymeimmunoassay for serum erythropoietin (Epo) and investigated relationship between Epo levels and hematological disorders. This method has several advantages including simplicity, high sensitivity, good precision. Moreover, the procedure requires only about 2.5 hours. Samples from 134 healthy subjects showed a normal logarithmic distribution, and its normal range was 4.5 approximately 21.3 mU/ml. The levels of Epo in normal subjects and various hematological disorders were as follows: 10.5 +/- 4.1 (mean +/- SD mU/ml) in normal subjects, 2.2 +/- 1.7 in polycythemia vera (PV), 6.1 +/- 3.1 in essential thrombocythemia, 17.8 +/- 27.3 in chronic myelogeneous leukemia, 3.6 +/- 1.8 in stress erythrocytosis, 39.4 and 14.1 in two cases of primary myelofibrosis, 1289 +/- 4798 in iron deficiency anemia and 6564 +/- 10870 in aplastic anemia. In patients with PV, serum Epo were low and did not correlate with hemoglobin concentration. However, inverse correlation was found between changes of Epo levels and hemoglobin levels in most patients. In cases in which PV progressed into myelofibrosis, anemia developed and Epo levels increased accordingly. These results suggest that the method is thought to be useful and reliable for the diagnosis and monitoring of PV and related hematological disorders.

Inhibitory effects of pectic substances on activated hyaluronidase and histamine release from mast cells

In this paper, we report the effect of pectic substances and D-galacturonic acid, the main constituent of pectic substances, on activated hyaluronidase and histamine release from mast cells. Although D-galacturonic acid itself showed no inhibition, IC50 values of hyaluronidase inhibition were correlated with the D-galacturonic-acid content of pectic substances. It was thought that the polymerization of D-galacturonic acid was necessary for inhibition of activated hyaluronidase. This type of inhibition was suggested to be non-competitive by the Lineweaver-Burk plot. Furthermore, pectic substances, including those purified from Gymnema sylvestre, inhibited histamine release from isolated rat peritoneal mast cells, which had been induced by the antigen. These results suggest that pectic substances may have anti-allergic activities.

[Lobular carcinoma of the male breast--a case report]

Lobular carcinoma of the male breast is very rare, because lobules do not exist in the male mammary gland. Seven cases of lobular carcinoma of the male breast have been reported in Europe and U.S.A., although no case in Japan. We encountered a very rare case of the lobular carcinoma of 74-year-old male breast. Histopathological examinations of both primary tumor and recurrent tumors of the skin led to the diagnosis of lobular carcinoma.

A new method of hernioplasty for adult groin hernias centering on repair of the transversalis fascia

A new method of hernioplasty for adult groin hernias centering on repair of the transversalis fascia was assessed by a questionnaire conducted every five years on adult patients who had received the above operation. The efficacy of this method was evaluated in terms of the postoperative quality of life and prevention of recurrence of groin hernias. Over the last 9 years, 834 adult patients with 921 groin hernias, including bilateral lesions, have undergone the above procedure and overall, favorable results were obtained, with only one case of recurrence (0.1 per cent) being reported. Contralateral herniation, which has been often reported following Bassini's or Hatakoshi's method, was found in only one of our patients although the number of patients who complained of pain in the operated region was comparatively high, being 51 cases or 11.4 per cent.

Interaction of 3,4,3',4'-tetrachlorobiphenyl metabolites formed by cytochrome P-450 in vitro with rat erythrocytes

Incubation of 14C-labeled 3,4,3',4'-tetrachlorobiphenyl (TCB) with a reconstituted monooxygenase system containing cytochrome P-450 isolated from 3-methylcholanthrene (MC)-treated rats caused an increase in incorporation of radioactivity to added rat erythrocytes and resulted in covalent binding of reactive metabolites to hemoglobin. Both increases in incorporation and covalent binding to the proteins were dependent on incubation time and required cytochrome P-450-linked monooxygenase activity. In the absence of erythrocytes, the reactive TCB metabolites bound to cytochrome P-450, NADPH-cytochrome P-450 reductase, and high-molecular weight aggregates, as determined by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis, whereas inclusion of the cells in the reaction mixture caused marked alkylation of hemoglobin and a decrease in binding to the electron transfer proteins. Several metabolites other than protein-bound metabolites were detected by thin-layer chromatography; some were found to be incorporated into the erythrocytes while others were not. These results suggest that several TCB metabolites formed by cytochrome P-450 can interact with rat erythrocytes in vitro, and that these interactions may be responsible for the persistence of TCB metabolites in blood observed in vivo.

Comparative studies on distribution and covalent tissue binding of 2,4,2',4'- and 3,4,3',4'-tetrachlorobiphenyl isomers in the rat

The 14C-labeled tetrachlorobiphenyl (TCB) isomers 2,4,2',4'-tetrachlorobiphenyl (2,4,2',4'-TCB) and 3,4,3',4'-tetrachlorobiphenyl (3,4,3'4'-TCB) were administered orally to rats, and distribution and covalent binding were measured in several organs. Marked differences in distribution and covalent binding of the two TCBs were observed. The accumulation and retention of 2,4,2',4'-TCB in adipose tissue were much higher than those of 3,4,3',4'-TCB, although the level of radioactivity in the blood was consistently higher in 3,4,3',4'-TCB treated rats. The radioactivity bound in covalent linkages with cellular macromolecules in several tissues was also measured. The data obtained indicated that covalent binding was higher in 3,4,3',4'-TCB treated rats than in those treated with 2,4,2',4'-TCB, particularly in liver and blood components. These results suggest that the two TCB isomers have different pharmacokinetic properties in rats, and the association of covalent binding with 3,4,3',4'-TCB-induced toxicities might be important. In addition, we found that repeated oral dosing with the two TCB isomers caused an increase in in vitro liver microsomal generation of reactive metabolites of TCBs, indicating that the microsomal enzyme system is likely to play an important role in the in vivo covalent binding of TCB.

Activation of 3,4,3',4'-tetrachlorobiphenyl to protein-bound metabolites by rat liver microsomal cytochrome P-448-containing monooxygenase system

The specificity of two major types of cytochrome P-450 of rat liver microsomes induced by phenobarbital (PB) and 3-methylcholanthrene (MC) toward activation of three 14C-labeled tetrachlorobiphenyl (TCB) isomers to protein-bound metabolites was examined by intact microsomal and reconstituted monooxygenase systems. The monooxygenase system containing PB-inducible form(s) of cytochrome P-450 was much more active than those inducible by MC in activating two TCB isomers, i.e., 2,4,2',5'-[14C]TCB, for the binding reaction. However, the binding of 3,4,3',4'-[14C]TCB was catalyzed most actively by the system containing a MC-inducible (P-448 type) cytochrome P-450 from rat liver microsomes. Thus two forms of cytochrome P-450 had different substrate specificities for the metabolism of TCB. In another series of experiments, the site of protein molecule bound to TCB metabolites was examined by the cytochrome P-448-containing reconstituted system with 3,4,3',4'-[14C]TCB as substrate. The following lines of evidence supported the hypothesis that the active metabolites of TCB bind covalently to cysteine residues of protein molecules a) TCB-binding activity was strongly inhibited by thiol compounds such as cysteine and glutathione and b) of the various kinds of proteins tested as target for TCB metabolites, only those which contained free sulfhydryl groups on the protein molecule were radiolabeled. Moreover, we found that during the metabolism of 3,4,3',4'-TCB, the heme content of the reconstituted system was lowered, probably reflecting the alkylation of the sulfhydryl groups in the active sites of cytochrome P-448.