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R Ogata

Publications and source records attributed to R Ogata.

At least 19 recordsLinked to original sources
PubMed2001

Two-generation reproductive toxicity study of tributyltin chloride in female rats.

A two-generation reproductive toxicity study of the effects of tributyltin chloride (TBTCl) was conducted in female rats using dietary concentrations of 5, 25, and 125 ppm TBTCl. Reproductive outcomes of dams (number and body weight of pups and the percentage of live pups) and the growth of female pups (the day of eye opening and body weight gain) were significantly decreased in the 125 ppm TBTCl group. A delay in vaginal opening and impaired estrous cyclicity were also observed in the 125 ppm TBTCl group. However, an increase in anogenital distance was found in all TBTCl groups on postnatal d 1. A dose-effect relationship was observed in TBTCl-induced changes in anogenital distance. These results indicate that the whole-life exposure to TBTCl affects the sexual development and reproductive function of female rats. In addition, the TBTCl-induced increase in anogenital distance seems to suggest it may exert a masculinizing effect on female neonates. However, the concentrations of TBTCl used in this study are not environmentally relevant.

Analysis of Variance↗
PubMed2001

Exposure to bisphenol A during the fetal and suckling periods disrupts sexual differentiation of the locus coeruleus and of behavior in the rat.

This study tested the effect of exposure to bisphenol A (BPA) early in life on the sexual differentiation in the brain and behavior in Wistar rats. We administered BPA only to mother rats during pregnancy and lactation at a dosage of approximately 1.5 mg/kg per day far less than the no-observed-adverse-effect level (NOAEL; 50 mg/kg per day). Control female offspring showed a higher activity, a lower avoidance memory, and larger locus coeruleus than the male controls, while the BPA-exposed group did not show any sexual dimorphism. BPA did not affect the reproductive organs or sex hormones. Our results suggest that the current methods to determine the NOAEL of artificial industrial chemicals may not be sufficient to detect a disruption of the sexual differentiation in the brain.

Animals↗
PubMed2001

Estrogen upregulates nitric oxide synthase expression in cultured rat hepatic sinusoidal endothelial cells.

BACKGROUND/AIMS: Estrogen receptor (ER) is present in vascular endothelial cells and estrogen promotes nitric oxide (NO) synthesis, which relaxes smooth muscle cells. It is also speculated that NO is synthesized by estrogen in hepatic sinusoidal endothelial cells (SECs). Here we investigated the localization of ER and endothelial cell nitric oxide synthase (ecNOS), and determined 17beta-estradiol (E2)-induced ecNOS expression in normal rat SECs. METHODS: Cultured SECs were used. Fluorescence intensities of ecNOS were measured by immunofluorescence using a confocal laser-scanning microscope. E2 was added (100 pg/ml) to the culture medium, and the expressions of ecNOS mRNA and protein were analyzed by reverse-transcription polymerase chain reaction and Western blotting. NO production in cultured SECs was examined using diaminofluorescein-2 diacetate as a fluorescent indicator for NO. RESULTS: Immunolocalization of ER and ecNOS in normal liver was demonstrated in endothelial cells lining the hepatic sinusoids. ER and ecNOS were localized in the nuclei and cytoplasm of cultured SECs, respectively. The mRNA expression of ecNOS in cultured SECs was increased after 6 h, and the protein expression of ecNOS was increased 24 h after E2 stimulation. The fluorescence intensity of NO in cultured SECs was increased by E2 stimulation compared with untreated control cells. CONCLUSIONS: These results suggested that ER is present in SECs, and estrogen upregulates NO production in SECs. E2 may be involved in the regulation of the hepatic sinusoidal microcirculation.

Animals↗
PubMed2001

Two-generation reproductive toxicity study of tributyltin chloride in male rats.

A 2-generation reproductive toxicity study of tributyltin chloride (TBTCl) was conducted in male rats using dietary concentrations of 5, 25, and 125 ppm TBTCl to evaluate its effect on sexual development and the reproductive system. F1 males were killed on postnatal day 119 and F2 males were killed on postnatal day 91. TBTCl affected the male reproductive system of rats. The weights of the testis and epididymis were decreased and homogenization-resistant spermatid and sperm count were reduced mainly in the 125 ppm TBTCl group. Histopathologic changes were also observed in the testis of this group and included vacuolization of the seminiferous epithelium, spermatid retention, and delayed spermiation. However, the changes were minimal in nature. The weight of the ventral prostate was decreased to 84% of the control value in the 125 ppm group in the F1 generation and decreased to 84 and 69% of the control value in the 25 ppm and 125 ppm TBTCl groups, respectively, in the F2 generation. The serum 17beta-estradiol concentration was also decreased to 55% of the control value in the 125 ppm group in the F1 generation and decreased to 78 and 57% of the control value in the 25 ppm and 125 ppm TBTCl groups, respectively, in the F2 generation. However, the serum concentrations of luteinizing hormone (LH) and testosterone were not decreased in these groups. These changes corresponded with those caused by aromatase inhibition and therefore TBTCl might be a weak aromatase inhibitor in male rats.

Animals↗
PubMed2000

Onset of spermatogenesis is accelerated by gestational administration of 1,2,3,4,6,7-hexachlorinated naphthalene in male rat offspring.

We treated pregnant rats with 1 microg/kg body weight/day 1,2,3,4,6,7-hexachlorinated naphthalene (1,2,3,4,6,7-HxCN) on days 14-16 of gestation and examined the effects on the reproductive systems of their male offspring at various phases of sexual maturation. Sperm count in the cauda epididymidis did not change in 1,2,3,4,6, 7-HxCN-treated rats on postnatal day 89, the age of sexual maturity, but the sperm count in the cauda epididymidis did increase to approximately 180% of the control value on postnatal day 62. In addition, homogenization-resistant testicular spermatids increased to approximately 160% of the control value on postnatal day 48, and the percent of postmeiotic tubules increased to approximately 190% of the control value on postnatal day 31 in this group. These results indicate that the onset of spermatogenesis was accelerated in the 1,2,3,4,6,7-HxCN rats. Serum concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) had already reached the maximum level on postnatal day 31 in the 1,2,3,4,6, 7-HxCN group, suggesting that the onset of LH and FSH secretions from the pituitary gland was also accelerated and that this endocrine disruption was the cause of early onset of spermatogenesis in this group. In the fat of 1,2,3,4,6,7-HxCN-treated dams, 5.75+/-2.81 ppb 1,2,3,4,6,7-HxCN was detected when offspring were weaned. This concentration was 5-10 times higher than that found in human adipose tissue.

Adipose Tissue↗
PubMed2000

Angiogenesis inhibitor TNP-470 suppresses the progression of experimentally-induced hepatocellular carcinoma in rats.

We evaluated the effects of angiogenesis inhibitor, TNP-470, on hepatocellular carcinoma (HCCs) induced by a choline-deficient L-amino acid defined (CDAA) diet in rats. Male Fisher 344 rats were fed CDAA for 68 weeks. Rats were treated by subcutaneous injection of TNP-470 (15 mg/kg) or saline (control) three times per week from 53 to 68 weeks. At the end of the experiment, we determined the frequency and size of HCCs and glutathione S-transferase placental form (GSTP)-positive lesions, histology of liver cirrhosis, liver function, and liver weight per body weight. We also determined, using histologic and immunohistochemical semiquantification analyses, the degree of vascularity, apoptosis and proliferation in HCC and adjacent tissues. Treatment with TNP-470 resulted in a reduction of the size and frequency of HCC compared to untreated rats. However, TNP-470 did not influence the histology of liver cirrhosis and liver function. The liver weight per body weight of TNP-470-treated rats was slightly heavier in comparison with that of the controls. Treatment with TNP-470 significantly reduced tumor vascularity relative to the controls. There were no significant differences in the Ki-67 labeling index of HCCs between TNP-470 treated and control rats. The frequency of apoptotic hepatoma cells in TNP-470-treated rats was higher than in control rats. Our results indicate that TNP-470 suppresses the progression of CDAA-induced HCCs in rats through inhibition of angiogenesis, and suggest that TNP-470 might be useful clinically for HCCs.

Angiogenesis Inhibitors↗
PubMed1999

Erythropoietic protoporphyria with fatal liver failure.

A 33-year-old woman with a history of photosensitivity, persistent abdominal pain, and liver dysfunction was admitted to our department because of abdominal pain and progression of liver dysfunction. On admission, levels of protoporphyrin and coproporphyrin within erythrocytes were markedly increased. Autofluorescent erythrocytes were also detected, leading to a diagnosis of erythropoietic protoporphyria. A liver biopsy specimen revealed cirrhosis with dark brown granules filling hepatocytes, bile canaliculi, and bile ductules. Transfusion of washed erythrocytes, hemodialysis, and administration of cholestyramine and beta-carotene transiently improved levels of porphyrins and liver function. The patient died of rupture of esophageal varices followed by multiple organ failure. However, the treatments were believed to have extended survival.

Adult↗
PubMed1999

Increased expression of membrane type 1 matrix metalloproteinase and matrix metalloproteinase-2 with tumor dedifferentiation in hepatocellular carcinomas.

Destruction of the extracellular matrices is required for tumor invasion and metastasis. Matrix metalloproteinase-2 degrades type IV collagen and laminin, major components of the basement membrane. Membrane type 1 matrix metalloproteinase activates the latent form of matrix metalloproteinase-2. We studied changes in membrane type 1 matrix metalloproteinase and matrix metalloproteinase-2 expression in relation to the tumor differentiation of hepatocellular carcinomas. Activity of matrix metalloproteinase-2 was also evaluated in hepatocellular carcinomas and noncancerous tissues. Overall, 37 hepatocellular carcinomas were studied. Expression of membrane type 1 matrix metalloproteinase and matrix metalloproteinase-2 was determined by either immunohistochemistry (n=37) or in situ hybridization (n=6). Changes in membrane type 1 matrix metalloproteinase and matrix metalloproteinase-2 expression were evaluated in relation to tumor differentiation. Gelatinolytic activities were analyzed by gelatin zymography (n=4). Membrane type 1 matrix metalloproteinase and matrix metalloproteinase-2 were detected in hepatoma cells and stromal cells. In addition, these matrix metalloproteinases were detected in the same hepatoma cells. Increased expression of membrane type 1 matrix metalloproteinase and matrix metalloproteinase-2 was associated with tumor dedifferentiation. The active form of matrix metalloproteinase-2 was more strongly expressed by hepatocellular carcinomas than by noncancerous tissues. These findings indicate that increased expression of membrane type 1 matrix metalloproteinase and matrix metalloproteinase-2 was associated with tumor dedifferentiation, suggesting that these matrix metalloproteinases are intimately involved in the invasion of hepatocellular carcinomas.

Adult↗
PubMed1999

Integrin alpha6beta1 plays a significant role in the attachment of hepatoma cells to laminin.

BACKGROUND/AIMS: Tumor invasion and metastasis consist of a series of complex events. During this process, the ability of tumor cells to adhere to laminin, a major component of basement membranes, is required at various steps. The expression of laminin-binding integrins and the extent of tumor metastasis and progression appear to be related. In hepatocellular carcinoma, increased expression of laminin-binding integrins is observed. However, little is known concerning the possible functional interactions between laminin-binding integrins and laminin. Therefore, we investigated the participation of laminin-binding integrins in the attachment of hepatoma cells to laminin. METHODS: Human hepatoma cell lines (KIM-1, KYN-1, 2) were used. We investigated the expression of integrin alpha1, alpha2, alpha3, alpha6, beta1, and beta4 subunits on hepatoma cells by immunocytochemical and flow cytometric analysis. Participation of these integrin subunits in the attachment of hepatoma cells to laminin was evaluated by an inhibition of cell adhesion assay. RESULTS: Integrin alpha1, alpha2, alpha3, alpha6 and beta1 subunits were expressed at the marginal areas of hepatoma cells, while the integrin beta4 subunit was scarcely detected. Laminin promoted the attachment of hepatoma cells in a dose-dependent manner. Although anti-integrin alpha1, alpha2, beta3 and beta4 subunit antibodies did not inhibit cell attachment to laminin, anti-integrin alpha6 and beta1 subunit antibodies inhibited the attachment by 50% or more. CONCLUSIONS: These findings indicate that integrin alpha6beta1 is very important in the attachment of hepatoma cells to laminin, suggesting the participation of this integrin in metastasis and invasion of hepatoma cells.

Carcinoma, Hepatocellular↗
PubMed1999

Changes in coagulation factors and fibrinolytic components of postmenopausal women receiving continuous hormone replacement therapy.

OBJECTIVE: The effect of hormone replacement therapy (HRT) on coagulation factors and fibrinolytic components in postmenopausal women was studied for 6 months to elucidate whether continuous HRT has an influence on thrombosis. METHODS: One hundred and thirty-four postmenopausal women were divided into three groups according to treatment: 39 women who had undergone hysterectomy and oophorectomy received 0.625 mg/day of conjugated equine estrogen (CEE) continuously (CEE therapy), 48 postmenopausal women received both 0.625 mg/day of CEE and 2.5 mg/day of medroxyprogesterone acetate (MPA) continuously (CEE/MPA therapy) and 47 postmenopausal women received placebo as control. The following variables were measured before treatment as well as after 1, 3 and 6 months of treatment: factor VII activity, protein C activity, fibrinogen level, antithrombin III activity, plasminogen activator inhibitor-1 (PAI-1) level and the plasma concentration of tissue-type plasminogen activator (t-PA). RESULTS: After 1 month of treatment, protein C activity increased by 9.6% and 11.4% of the initial value (p < 0.05), fibrinogen level decreased by 7.8% and 6.1% of the initial value (p < 0.05) and PAI-1 decreased by 19.4% and 14.3% of the initial value (p < 0.05) in the CEE therapy group and the CEE/MPA therapy group, respectively. Factor VII activity increased by 10.1% of the initial value (p < 0.05) in the CEE therapy group only. Antithrombin III and t-PA levels did not change throughout either treatment. CONCLUSION: Except for an increase in factor VII activity in the case of continuous CEE therapy, continuous HRT had no unfavorable effects on either coagulation factors or fibrinolytic components.

Antithrombin III↗
PubMed1999

OK-432 treatment increases matrix metalloproteinase-9 production and improves dimethylnitrosamine-induced liver cirrhosis in rats.

Kupffer cells are major matrix metalloproteinase-producing cells in the liver. The production of metalloproteinases in Kupffer cells may contribute to the improvement of liver fibrosis inducing liver cirrhosis. In this study, we examined the effect of the OK-432 (a biological response modifier) on the dimethylnitrosamine-induced liver cirrhosis in rats. Dimethylnitrosamine (10 microg/ml) was injected intraperitoneally into 20 male Wistar rats 3x/week for 4 weeks. For the subsequent 4 weeks, the animals were injected with saline (1 ml, 1x/week) (Group I, n=10) or OK-432 (1 Klinishe Einheit, 1x/week) (Group II, n=10). The control rats were injected with 1 ml saline for the initial 4 weeks and subsequent 4 weeks (Group III, n=10). The degree of hepatic fibrosis, the immunolocalization of type IV collagen, hyaluronic acid, and alpha-smooth muscle actin, and the mRNA expression by Northern blotting and the activity by gelatin zymography of metalloproteinase-9 were evaluated. Serum aminotransferase, hyaluronic acid, interleukin-1beta and tumor necrosis factor-alpha levels were measured. The deposition of á-smooth muscle actin and extracellular matrix containing type IV collagen and hyaluronic acid was markedly suppressed by OK-432. The mRNA expression and the activity of metalloproteinase-9 were markedly increased by OK-432. The serum aminotransferase and hyaluronic acid levels were decreased by OK-432. The serum interleukin-1 and tumor necrosis factor-alpha values were lower than the detectable limit in all samples from all three groups. These results indicate that OK-432 increased the production of metalloproteinase-9 and improved the rat dimethylnitrosamine-induced liver cirrhosis. OK-432 is suggested to be useful for the treatment of liver cirrhosis.

Actins↗
PubMed1998

Differential time-related effects of conjugated equine estrogen on bone metabolism in oophorectomized women.

OBJECTIVE: The effects of conjugated equine estrogen (CEE) on bone mineral density (BMD) and biochemical indices of bone remodeling in oophorectomized women were studied for 3 years during estrogen replacement therapy (ERT) to investigate whether 0.625 mg/day of CEE alone prevent acute bone loss in the early stage of surgical menopause. METHODS: We divided the subjects into three groups according to interval between oophorectomy and the start of ERT (group 1: less than 2 years after surgery, n = 31; group 2: 2-5 years after surgery, n = 29; and group 3: more than 5 years after surgery, n = 27). Vertebral BMD was measured using dual energy X-ray absorptiometry (DEXA). Two biochemical indices of bone metabolism, urinary deoxypyridinoline (DPyr) and serum intact human osteocalcin (hOC) were also measured. RESULTS: In group 1, continuous ERT with 0.625 mg/day of CEE could not prevent a BMD decrease within the first year. However, by the end of the second year, BMD was restored to the pre-ERT. The same dosage of CEE significantly increased BMD in groups 2 and 3 by the end of the first year. DPyr and hOC levels both decreased dramatically in the initial 6 months of therapy and were stable thereafter. CONCLUSION: In the initial 2-year period after oophorectomy, 0.625 mg/day of CEE alone could not prevent acute bone loss suggesting that additional therapy for the prevention of osteoporosis may be needed.

Absorptiometry, Photon↗
PubMed1998

Treatment of bone loss in oophorectomized women with a combination of ipriflavone and conjugated equine estrogen.

OBJECTIVE: We previously reported that 0.625 mg/day of conjugated equine estrogen (CEE) could not prevent acute bone loss in the first year after oophorectomy. The effect of additional administration of ipriflavone on bone mineral density (BMD) and biochemical indices of bone remodeling were studied to investigate whether concurrent use of CEE and ipriflavone prevent acute bone loss in the early stages following surgical menopause. METHODS: One-hundred and sixteen oophorectomized women were randomly divided into four groups according to treatment; group 1: placebo, n = 30; group 2: CEE (0.625 mg/day), n = 29; group 3: ipriflavone (600 mg/day), n = 30; group 4: CEE (0.625 mg/day) plus ipriflavone (600 mg/day), n = 27. Vertebral BMD was measured using dual energy X-ray absorptiometry (DEXA) and two biochemical indices of bone metabolism, urinary pyridinoline (Pyr) and serum intact human osteocalcin (hOC), were also measured before, 24 weeks, and 48 weeks after initiation of treatment. RESULTS: BMD was reduced 48 weeks after treatment by 6.1, 3.9 and 5.1% in groups 1-3, respectively, but by only 1.2% in group 4. Pyr decreased by 49.5, 32.0 and 41.5% in groups 2-4, respectively. hOC also decreased by 45.2 and 21.6% in groups 2 and 4, but increased by 40.5% in group 3, suggesting an inhibitory action of CEE and ipriflavone on the turnover of bone metabolism and stimulatory action of ipriflavone on bone formation. CONCLUSION: Concomitant use of ipriflavone with CEE from an early stage after oophorectomy inhibited bone loss and was considered to be effective in maintaining bone mass after oophorectomy.

Absorptiometry, Photon↗
PubMed1998

Type IV collagen and laminin enhance the motility, adhesion, and proliferation of hepatoma cells.

Type IV collagen and laminin, major components of the basement membrane, are involved in several biologic activities. In malignant tumors, cell-matrix interactions are very important for tumor invasion and metastasis. In hepatocellular carcinoma, these matrices are present around hepatoma cells. However, there is little known how these matrices influence on the behavior of hepatoma cells. In this study, we investigated the participation of type IV collagen and laminin in the motility, adhesion, and proliferation of hepatoma cells using three different human hepatoma cell lines (KYN-1, 2, 3). The production of type IV collagen and laminin was investigated by immunoelectron microscopy. The effects of type IV collagen and laminin on hepatoma cell migration, adhesion, and proliferation were evaluated by the haptotactic migration assay, phagokinetic track assay, an adhesion assay, and a 3H-thymidine incorporation assay. Immunoelectron microscopy showed the production of type IV collagen and laminin by hepatoma cells. Type IV collagen and laminin enhanced haptotactic migration, chemokinesis, adhesion, and thymidine incorporation by hepatoma cells. The combination of type IV collagen and laminin had the most pronounced effects on these biologic activities. These results indicate that type IV collagen and laminin promote hepatoma cell motility, adhesion, and proliferation in an autocrine manner, suggesting enhancement of invasion and metastasis of hepatoma cells by these basement membrane components in vivo.

Carcinoma, Hepatocellular↗
PubMed1998

Serum carboxy-terminal cross-linked telopeptide of type I collagen reflects bone metastasis in hepatocellular carcinoma.

Carboxy-terminal telopeptide of type I collagen (ICTP) is a degradation product of type I collagen. In this study, we investigated the usefulness of measuring the serum ICTP concentration for diagnosing and monitoring bone metastasis from hepatocellular carcinoma (HCC). The serum concentrations of ICTP, type I procollagen carboxy-terminal propeptide (PICP), type III procollagen aminoterminal propeptide (PIIIP), type IV collagen (Ty IV), type IV collagen 7S-domain (7S), and hyaluronic acid (HA) were measured in patients with liver cirrhosis, HCC with or HCC without bone metastasis, and in healthy controls. The diagnostic efficiency of the serum ICTP and fibrosis marker levels in the HCC patients with and without bone metastasis was evaluated using receiver operating characteristic curves. We also retrospectively examined the changes in the serum ICTP levels before and after bone metastasis in the HCC patients. The serum ICTP level was significantly higher in the HCC patients with bone metastasis than in the patients with other diseases and the healthy controls. The serum PICP, PIIIP, Ty IV, 7S and HA levels of the HCC patients with bone metastasis did not differ significantly from those of the patients without bone metastasis. The diagnostic efficiency for HCC with bone metastasis was 87% for ICTP, 51% for PICP, 65% for Ty IV, 55% for PIIIP and 51% for HA. During the follow-up, the changes in the serum ICTP values paralleled the behavior of bone metastasis. These results indicate that the measurement of serum ICTP concentration is useful for detecting and monitoring HCC patients with bone metastasis.

Adult↗
PubMed1998

[The diagnosis of the early stage of hepatocellular carcinoma by US-angiography with intraarterial Albunex (sonicated serum albumin) infusion].

Contrast-enhanced ultrasonography (arterial infusion) has been clinically established as a qualitative diagnosis imaging tool for hepatocellular carcinoma (HCC). Contrast-enhanced ultrasonography (CEUS) was performed after of Albunex (sonicated serum albumin) or Carbon Dioxide (CO2) microbubble by hand, into the hepatic artery as a diagnostic modality for the early HCC. Here, we discussed the diagnosis of the early HCC by CEUS using Albunex as a contrast medium. Briefly, a diagnosis of the early HCC was made CEUS examination of the hemodynamics of the arteries showed a hypovascular pattern. And tumor size was under 20 mm in diameter, the histopathologic examination was essential to reach a final diagnosis, well-differentiated HCC.

Albumins↗
PubMed1997

Inhibitory effects of genistein on ATP-sensitive K+ channels in rabbit portal vein smooth muscle.

1. Effects on the pinacidil-induced outward current of inhibitors of tyrosine kinases and phosphatases were investigated by use of a patch-clamp method in smooth muscle cells of the rabbit portal vein. 2. A specific tyrosine kinase inhibitor, genistein, inhibited the pinacidil-induced current in a concentration-dependent manner with an IC50 of 5.5 microM. Superfusion of Ca2+-free solution did not affect this inhibitory effect of genistein. At higher concentrations, genistein inhibited the voltage-dependent Ba2+ and K+ currents with IC50 values of > 100 microM and 75 microM respectively. Tyrphostin B46 (30 microM), a tyrosine kinase inhibitor, also inhibited the pinacidil-induced current by 70% of the control. 3. Sodium orthovanadate (100 microM), an inhibitor of tyrosine phosphatase, slightly but significantly enhanced both the pinacidil-induced and delayed rectifier K+ currents. Daidzein (100 microM), an inactive analogue of genistein, did not inhibit these currents. 4. Neither herbimycin A (1 microM), lavendustin A (30 microM), tyrphostin 23 (10 microM), which are also tyrosine kinase inhibitors, nor wortmannin (10 microM), a phosphatidylinositol 3-kinase inhibitor, had an effect on either the pinacidil-induced or delayed rectifier K+ currents. Epidermal growth factor (EGF; 1 microg ml(-1)) did not induce an outward current or enhance the pinacidil-induced current. 5. Pinacidil alone, in the cell-attached configuration, or pinacidil with GDP, in the inside-out configuration, activated a 42 pS channel in the smooth muscle cells of the rabbit portal vein. Genistein (30 microM) reduced the channel's open probability without inducing a change in unitary conductance at any holding potential (-30 to +20 mV). 6. In the inside-out configuration, genistein at 30 microM did not change the mean channel open time, but reduced the burst duration. At 100 microM genistein abolished channel opening. The inhibitory potencies with which 30 and 100 microM genistein acted on the unitary current of the ATP-sensitive K+ channel were similar to those seen in the whole-cell voltage-clamp configuration. 7. Although direct inhibitory actions of genistein on the ATP-sensitive K+ channels are not ruled out, our results suggest that a protein tyrosine kinase may play a role in the regulation of ATP-sensitive K+ channel activity in the rabbit portal vein.

Animals↗