Sex-specific cytochrome P450 as a cause of sex- and species-related differences in drug toxicity

Male rats are the most frequently used experimental animals in drug toxicity tests. However, there are clear sex-related differences in toxicity of various drugs and chemicals in rats. These differences, in most cases, are closely connected with the sex-related differences in hepatic drug metabolisms. Recent studies indicate the existence of sex-specific cytochrome P450, such as P450-male (2C11) and P450-female (2C12) and P450(6) beta (3A2) in rat livers, and also show that their expression levels are markedly different between male and female rats. The expressions of sex-specific P450s are regulated by growth hormone, thyroid hormone, sex hormones and other chemicals. On the other hand, there are no or few cytochrome P450s that show the sex-related differences in species other than rats and mice. Although there are orthologous cytochrome P450s in viewpoints of amino acid sequence and substrate specificity in experimental animal species and humans, their expressions are not regulated by hormonal factors in most of the species. These differences may cause clear species differences, if male animals are used, in the toxicity caused by various drugs and chemicals. Thus we can predict the sex-related difference in drug toxicity on the basis of difference in the expression levels of sex-specific cytochrome P450s.

[Gianturco expandable metallic stents in the treatment of tumor thrombus in portal vein--preliminary clinical experience]

Two cases of hepatocellular carcinoma with protal vein invasion (Vp3) were successfully treated by Gianturco expandable metallic stents (GEMS). Each case was treated through the different approach, i.e. the percutaneous transhepatic or ileocolic venous route. GEMS was easily expanded within the protal vein and carcinoma thrombi were pushed against the walls, resulting in increase of portal blood flow. The GEMS might improve the impaired portal blood flow with hepatic failure and esophagogastric varices, in spite of the possibilities of dissemination and ingrowth of carcinoma thrombi.

Hormonal regulation of rat renal cytochrome P450s by androgen and the pituitary

The hormonal regulation of rat renal cytochrome P450s, P450 4A2 (K-5) and K-2, was investigated. The level of P450 4A2 in male rats was five times that in female rats and accounted for some 90% of total cytochrome P450, measured photometrically. Lauric acid omega- and (omega-1)-hydroxylation activities of renal microsomes of male rats were also higher than those of female rats. The sex differences in lauric acid hydroxylation activity seemed to arise from the differences in P450 4A2 concentrations, according to an immunochemical study. P450 K-2 was a female-dominant form in rat kidneys. The level of P450 K-2 in renal microsomes of male rats was one-tenth that of P450 4A2. Castration of male rats decreased the levels of P450 4A2 and treatment of castrated male rats with testosterone reversed the decrease. The castration of male rats decreased the lauric acid hydroxylation of the renal microsomes to the level of female rats. The administration of testosterone to castrated male rats reversed the decrease. Hypophysectomy of male rats decreased the level of P450 4A2 and the administration of growth hormone reversed the decrease when intermittent injections mimicking the male secretory pattern were given, although continuous administration mimicking the female secretory pattern did not. Castration of male rats did not affect the level of P450 K-2, but testosterone decreased its level. Hypophysectomy of male rats increased the level of P450 K-2 and growth hormone decreased its level in hypophysectomized rats. These results suggested that the expression of P450 4A2 was regulated by androgen or growth hormone and regulation of P450 4A2 was different from that of P450 K-2. To explore the regulation of renal cytochrome P450 further, testosterone was given to control (intact) or hypophysectomized adult female rats. P450 4A2 was induced in the kidneys of both control and hypophysectomized female rats to close to the level of male rats. Thus, P450 4A2 was directly regulated by testosterone as well as growth hormone, and the regulation of the male-dominant form in rat kidneys was different from that of the male-specific form in the rat liver, which is regulated mostly by growth hormone.

Characterization of endogenous substrates for novel-type protein kinase C as well as conventional-type protein kinase C in primary cultured mouse epidermal cells

In primary cultured mouse epidermal cells, phorbol 12-myristate 13-acetate (PMA), which activates protein kinase C (PKC), induced changes in the phosphorylation levels of 10 proteins, termed KP-1 to -10, in two-dimensional PAGE. Seven of these proteins were phosphorylated and three were dephosphorylated. Similar changes were induced by other PKC activators, but not by inactive phorbol ester. Among these substrate proteins, phosphorylation of three proteins, i.e. KP-1 (pI 4.7/23,000 M(r)), KP-2 (pI 4.7/20,700 M(r)) and KP-10 (pI 4.7/25,500 M(r)) was markedly enhanced by PMA and inhibited by a potent PKC inhibitor staurosporine. In vitro phosphorylation studies and phosphoamino acid analysis, using these proteins as substrate and PKC preparations obtained from epidermal cell lysate, revealed that KP-1 and -2 were directly phosphorylated by Ca(2+)-, phospholipid-dependent protein kinase (conventional-type PKC; cPKC), but not by Ca(2+)-independent, phospholipid-dependent protein kinase (novel-type PKC; nPKC). On the other hand, KP-10 was mainly phosphorylated by nPKC in intact epidermal cells. These results indicate that cPKC and nPKC in epidermal cells have different substrate specificity for endogenous proteins and may induce different signal transduction.

[Spontaneous cerebrospinal fluid otorrhea in a normal inner ear. A case report]

A 49-year-old male with spontaneous cerebrospinal fluid (CSF) otorrhea, an extremely rare condition, is presented as the third reported case in Japan. The patient visited us complaining of sudden hearing loss and fullness of the ear on the left side. A tegmen defect of the posterior cranial fossa and CSF leakage from the fistula into the mastoid air cells, but a normal inner ear, were found by means of metrizamide CT. The fistula was surgically occluded with fascia temporalis and an artificial bone with fibrin glue. The CSF otorrhea from the tegmen defect was successfully stopped by this procedure and no recurrence has been observed. We discuss this extremely rare disease in this paper.

Protein kinase C-dependent and -independent actions of a potent protein kinase C inhibitor, staurosporine

12-O-Tetradecanoylphorbol 13-acetate (TPA), an activator of protein kinase C (PKC), induced ornithine decarboxylase (ODC) in primary cultured mouse epidermal cells. Staurosporine, a potent protein kinase C inhibitor, also induced ODC activity. Both TPA- and staurosporine-caused ODC inductions were markedly suppressed in the PKC-down-regulated cells. Another PKC inhibitor, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7), inhibited both TPA- and staurosporine-caused ODC inductions. H-7 by itself never induced ODC activity. Under our experimental conditions, staurosporine induced no detectable phosphorylation of endogenous proteins. TPA induced a translocation of PKC from cytosol to membrane whereas an optimal concentration of staurosporine to induce ODC did not induce an obvious translocation of PKC. Indomethacin, a cyclooxygenase inhibitor, inhibited staurosporine-caused ODC induction, but not TPA-caused ODC induction. Staurosporine induced specific morphological changes of epidermal cells both in normal and in PKC-down-regulated cells. These results indicate that staurosporine induces ODC activity in a PKC-dependent manner and morphological changes possibly through a PKC-independent mechanism. The mechanism of ODC induction caused by staurosporine may be in some way different from that caused by TPA.

Can the chest tube draining the pleural cavity with persistent air leakage be removed?

The pleural drain with persistent air leak in six selected patients after pulmonary surgery was clamped or removed without causing pulmonary collapse. In all the patients, air leak through the chest tube was present when speaking or coughing but not seen when breathing normally at rest or taking deep breaths. The fact that the chest tube could be removed in selected patients is explained by supposing the air leakage through an alveolopleural fistula is dependent on pressure difference between the alveoli and the pleural cavity, and this was confirmed in a rethoracotomy case for persistent air leak. Removal of the chest tube following the above-mentioned rationale would reduce the number of rethoracotomy cases for air leak and facilitate early removal of the chest tube in some patients.

Anthralin, a non-TPA type tumor promoter, synergistically enhances phorbol ester-caused prostaglandin E2 release from primary cultured mouse epidermal cells

Primary cultures of mouse epidermal cells (i.e., target cells of skin tumor promotion) stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA) release prostaglandin E2 within 30 min. Anthralin, a non-TPA type tumor promoter, also stimulated PGE2 release; however, no release was detectable at least up to 4 hr after the addition of anthralin. When the cells were incubated with TPA plus anthralin, both PGE2 and arachidonic acid release were synergistically enhanced. Other non-TPA type tumor promoters, i.e., chrysarobin, 7-bromomethylbenz[a]anthracene, benzoylperoxide, okadaic acid and palytoxin, did not potentiate the TPA-caused PGE2 release. In protein kinase C-down regulated cells, the synergistic stimulation of PGE2 and arachidonic acid release by TPA plus anthralin were not detected. Anthralin plus TPA did not alter the incorporation of arachidonic acid into cellular phospholipids. Cellular cyclooxygenase activity was increased 2 hr after TPA stimulation. Anthralin-caused increase in cyclooxygenase activity was detected at 6 hr after the addition of anthralin. Cyclooxygenase activity was synergistically increased by treating the cells with TPA plus anthralin. Cycloheximide and actinomycin D inhibited the increase in cyclooxygenase activity caused by anthralin or TPA plus anthralin. These results indicate that anthralin synergistically stimulates TPA-caused PGE2 release by synergistically increasing arachidonic acid release and cellular cyclooxygenase activity.

Polymorphism in stereoselective hydroxylations of mephenytoin and hexobarbital by Japanese liver samples in relation to cytochrome P-450 human-2 (IIC9)

1. Stereoselective 4'-hydroxylations of R-(--)-mephenytoin and S-(+)-mephenytoin were determined in liver microsomes of 19 Japanese subjects. 2. The content of P-450 human-2 assessed by Western-blots correlated with microsomal S-(+)-mephenytoin 4'-hydroxylation. Antibody raised against P-450 human-2 effectively inhibited microsomal S-(+)-mephenytoin 4'-hydroxylation, but was less efficient for inhibition of R-(--)-mephenytoin 4'-hydroxylation in extensive metabolizers, and 4'-hydroxylation of both mephenytoin enantiomers in poor metabolizers. 3. Similar results were observed on the stereoselective hydroxylations of R-(--)- and S-(+)-hexobarbital. Clear correlations were observed for the content of P-450 human-2 and microsomal R-(--)-hexobarbital 3'alpha-hydroxylation and S-(+)-hexobarbital 3'beta-hydroxylation. 4. Moreover, yeast microsomes expressing P-450 human-2 cDNA showed high stereoselectivities for hydroxylations of mephenytoin and hexobarbital similar to those observed in human liver. 5. Two other cytochromes P-450(IIC 9/10) expressed in yeast, whose cDNA were synthesized by site-directed mutagenesis from human-2 cDNA, showed no stereoselectivity for the hydroxylations of mephenytoin and hexobarbital, in spite of the modification of only two amino acid substitutions or deletions in the whole sequence. 6. Only a cytochrome derived from P-450 human cDNA corresponding to P-450 human-2 was expressed in human livers, the two cytochromes of the three related IIC9/10 forms were not expressed. 7. These findings indicate that P-450 human-2 is the major cytochrome P-450 responsible for the polymorphisms in stereoselective hydroxylations of mephenytoin and hexobarbital.

[Transjugular intrahepatic portosystemic stent shunt (TIPSS)]

Our first clinical experience of TIPSS made for a 52-year-old patient with recurrent life threatening variceal bleeding is described. Although shunt-making between the right hepatic vein and the right portal vein and placement of Gianturco-Rösch Z stents were successfully made without significant complication related to the procedure, sufficient decompression of the portal vein pressure was not obtained because of compression on these stents at the tortuous portion of the shunting tract. Some technical problems of the procedure are also discussed, especially about choice of metallic stents and puncture technique.

Endothelium-accelerated hyporesponsiveness of norepinephrine-elicited contraction of rat aorta in the presence of bacterial lipopolysaccharide

The role of the endothelium in the hyporesponsiveness of alpha-adrenoceptor-mediated contractions of the rat aorta was investigated. The norepinephrine-induced maximal contraction was diminished after repeated addition of the agonist. The hyporesponsiveness of the maximal contraction was endothelium dependent, being prevented by NG-monomethyl-L-arginine (0.5 mM), L-argininosuccinic acid (0.5 mM), puromycin (IC50 = 100 microM), actinomycin D (IC50 = 80 nM) but not by indomethacin, which suggests that nitric oxide (NO) synthase is induced. The sensitivity of the rings to NO-induced relaxation remained unchanged. The above-mentioned hyporesponsiveness of norepinephrine-induced maximal contractions of aorta rings was also observed after a 5-h incubation without norepinephrine. The agonist-independent hyporesponsiveness was also prevented by NG-monomethyl-L-arginine, puromycin and actinomycin D, which suggests that NO synthase is induced. Moreover, the norepinephrine-independent hyporesponsiveness was prevented by polymyxin B (10 micrograms/ml), which suggests that bacterial lipopolysaccharide (LPS) might be involved. The concentration of contaminating LPS was 89 +/- 11 ng/ml. When the concentration of contaminating LPS was reduced to 40-70 pg/ml, the hyporesponsiveness of the maximal contraction did not occur after repeated addition of norepinephrine or alter a 5-h incubation without the agonist. An addition of 30 or 100 ng/ml of E. coli lipopolysaccharide to the organ bath reproduced the hyporesponsiveness of the maximal contraction. After a 5-h incubation of aortic rings with 30 ng/ml LPS, only the endothelium-intact ring showed a reduced contraction. However, a 24-h incubation reduced the contraction even in the absence of endothelium.(ABSTRACT TRUNCATED AT 250 WORDS)

Sulfotransferase-mediated DNA binding of N-hydroxyarylamines(amide) in liver cytosols from human and experimental animals

Characteristics of cytosolic sulfotransferase-mediated binding of carcinogenic N-hydroxyarylamines(amide) have been investigated and compared among experimental animal species and humans in vitro. Human cytosols exhibited significant sulfating activities towards 2-hydroxyamino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (N-hydroxy-Glu-P-1), N-hydroxy-2-aminofluorene (N-hydroxy-AAF) and N-hydroxy-2-acetylaminofluorene (N-hydroxy-AAF), but had no detectable activity toward 2-hydroxyamino-3-methyl-imidazo[4,5-f]quinoline (N-hydroxy-IQ). Although the extent of the covalent binding of these N-hydroxyarylamines(amide) differed significantly among individuals, clear correlations were observed among the sulfation of N-hydroxyarylamines (amide) and also with p-nitrophenol sulfation. Hepatic cytosols from mouse, rat, guinea-pig, hamster, rabbit, dog and monkey also mediated the binding of N-hydroxy-Glu-P-1, N-hydroxy-AF and N-hydroxy-AAF, while only rat cytosols showed detectable DNA binding of N-hydroxy-IQ. Among the species examined, rat showed the highest capability for activating these N-hydroxyarylamines(amides). Significant sex-related differences were detected in rat, dog and monkey for all substrates examined, except N-hydroxy-IQ. Clear correlations were observed in the animal species between N-hydroxyarylamines(amide), but not with p-nitrophenol. Using an ion-exchange chromatographic system, sulfating activity of p-nitrophenol in human livers was separated into two fractions and the PAPS-dependent DNA binding of N-hydroxy-AF was supported mainly by the later fraction. On Western blots, an immunoreactive protein was detected in these fractions using an antibody raised against rat hepatic N-hydroxy-AAF sulfotransferase. The band was also detected in human hepatic cytosols with considerable individual variation in their amounts. These results indicate the involvement of a closely related form(s) of sulfotransferase in the PAPS-mediated activation of N-hydroxyarylamines(amide) in human as well as in the experimental animal species.

Phenotypic expression of carcinogen-initiated epidermal cells to tumor cells by 12-O-tetradecanoylphorbol-13-acetate in a manner dependent on 3T3 fibroblast-derived humoral factor(s)

Primary cultured newborn mouse epidermal cells cultured in the low Ca2+ (0.02 mM) medium showed typical basal cell morphology and proliferated as a monolayer. A stepwise increase in medium Ca2+ concentration induced terminal differentiation of epidermal cells. In the case of epidermal cells obtained from newborn mice transplacentally initiated with 7,12-dimethylbenz[a]anthracene (DMBA) or epidermal cells initiated in vitro by DMBA, a small number of rapidly growing cellular foci with epidermal morphology appeared and proliferated when the medium Ca2+ concentration was raised. Without increasing Ca2+ concentration, such foci never appeared. However, the Ca2+ concentration of the extracellular milieu of basal epidermal cells is known to be very low in in vivo epidermis. Under the low Ca2+ conditions, 12-O-tetradecanoylphorbol-13-acetate (TPA), a most potent skin tumor promoter, never induced rapidly growing cellular foci. When the initiated epidermal cells were co-cultured with 3T3 fibroblasts but without direct cell-to-cell contact, TPA induced rapidly growing cellular foci even under the low Ca2+ condition. Without initiation, such cellular foci hardly appeared. 3T3 fibroblasts induced only a very small number of cellular foci in the absence of TPA. Co-culture with mouse peritoneal macrophages was not effective in inducing such cellular foci, indicating that the effect is 3T3 fibroblast specific. The conditioned medium of 3T3 fibroblasts was also capable of inducing such cellular foci. Three of these rapidly growing cellular foci were cloned and designated as WYF-30, WYF-31 and WYF-32 respectively. All of these three cell lines grew rapidly in the normal (1.8 mM) Ca2+ medium, indicating that these cell lines were resistant to Ca(2+)-induced differentiation. In the low Ca2+ medium, the growth of these three cell lines was stimulated by TPA. All three cell lines formed colonies in soft agar. The number of colonies formed under the normal Ca2+ condition was larger than that formed under the low Ca2+ condition. Under the low Ca2+ condition, the colony formation of each cell line was augmented by TPA. All the cell lines formed tumors in nude mice. These results indicate that TPA induces phenotypic expression of dormant initiated cells to tumor cells in a manner dependent on 3T3 fibroblast-derived humoral factor(s).

Hepatic triiodothyronine sulfation and its regulation by growth hormone and triiodothyronine in rats

The regulatory mechanism of cytosolic sulfation of T3 has been studied in rat liver. Sulfation of T3 is sexually differentiated in adult rats of Sprague-Dawley (SD), Fisher 344, and ACI strains. In SD strain, the male animals showed 4 times higher sulfating activity than did the females. The specific activity was decreased by hypophysectomy of male adult rats, but was not affected in the females. Thus, the sex-difference was abolished in the hypophysectomized condition. Supplement of human GH intermittently twice daily for 7 days, to mimic the male secretory pattern, increased T3 sulfating activity in both sexes of hypophysectomized rats, whereas continuous infusion to mimic a female secretory pattern had no appreciable effect. Cytosolic sulfation of T3 was decreased by 25 to 30% by thyroidectomy or propylthiouracil treatment of male adult rats, and was restored by the supplementation of T3 (50 micrograms/kg daily for 7 days) to thyroidectomized rats. Administration of T3 in hypophysectomized rats almost completely restored the sulfating activity in the males and increased the activity in the females. Cytosolic T3 sulfation was inhibited by the addition of known inhibitors of phenol sulfotransferase, pentachlorophenol or 2,6-dichloro-4-nitrophenol. These results indicate a role of pituitary GH in hepatic sulfation of thyroid hormones in rats. The data obtained also raise the possibility that GH may modify the effect of thyroid hormones on the pituitary by a feed-back mechanism through changing the level of a sex-dominant phenol sulfotransferase(s) in rat livers. T3 was also sulfated in hepatic cytosols of mouse, hamster, rabbit, dog, monkey, and human.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurotransmitter release from synaptotagmin-deficient clonal variants of PC12 cells

Synaptotagmin (p65) is an abundant synaptic vesicle protein of neurons and contains regions similar to the regulatory domain of protein kinase C. These domains are thought to be involved in calcium-dependent interaction with membrane phospholipids during exocytosis. To assess the functional role of synaptotagmin, synaptotagmin-deficient clonal variants of PC12 cells were isolated. All of the variant cells released catecholamine and adenosine triphosphate in response to elevated intracellular concentrations of calcium, which suggests that synaptotagmin is not essential for secretion of catecholamine and adenosine triphosphate from PC12 cells.

Increases in NO2-/NO3- excretion in the urine as an indicator of the release of endothelium-derived relaxing factor during elevation of blood pressure

1. Under hormonally constant conditions, the effects of a sudden increase in blood pressure on the release of endothelium-derived relaxing factor were evaluated by measuring urinary excretion of NO2-/NO3- in rats with renal denervation. 2. Elevation of blood pressure from 136 +/- 2 to 153 +/- 3 mmHg by an aortic clamp below the renal arteries induced a significant increase in urinary excretion of NO2-/NO3- from 76.6 +/- 4.2 x 10(2) to 108.1 +/- 8.3 x 10(2) pmol min-1 g-1 kidney weight (P less than 0.05). 3. Infusion of NG-monomethyl-L-arginine (1 mg min-1 kg-1) without an aortic clamp raised mean blood pressure to a similar level; however, urinary excretion of NO2-/NO3- was decreased significantly. 4. During infusion of NG-monomethyl-L-arginine, aortic occlusion caused a significant increase in blood pressure without any changes in NO2-/NO3- excretion in the urine. 5. These results suggest that the formation of NO, an indicator of endothelium-derived relaxing factor release, was increased by mechanical pressure elevation without apparent changes in hormonal and neural factors.

Stimulus-induced accumulation of inositol tetrakis-, pentakis-, and hexakisphosphates in N1E-115 neuroblastoma cells

When [3H]inositol-prelabelled N1E-115 cells were stimulated with carbamylcholine (CCh) (100 microM), high K+ (60 mM), and prostaglandin E1 (PGE1) (10 microM), a transient increase in [3H]inositol pentakisphosphate (InsP5) accumulation was observed. The accumulation reached its maximum level at 15 s and had declined to the basal level at 2 min. CCh, high K+, and PGE1 also caused accumulations of [3H]inositol 1,4,5-trisphosphate [Ins(1,4,5)P3], [3H]inositol 1,3,4,6-tetrakisphosphate [Ins(1,3,4,6)P4], and [3H]inositol hexakisphosphate (InsP6). Muscarine and CCh induced accumulations of [3H]Ins(1,4,5)P3, [3H]-Ins(1,3,4,6)P4, [3H]InsP5, and [3H]InsP6 with a similar potency and exerted these maximal effects at 100 microM, whereas nicotine failed to do so at 1 mM. With a slower time course, CCh, high K+, and PGE1 caused accumulations of [3H]-inositol 1,3,4-trisphosphate [Ins(1,3,4)P3] and [3H]inositol 1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P4]. In an N1E-115 cell homogenate, [3H]Ins(1,4,5)P3, [3H]Ins(1,3,4,5)P4, and [3H]Ins(1,3,4)P3 were converted to [3H]InsP5 through [3H]-Ins(1,3,4,6)P4. The above results indicate that Ins(1,3,4,6)P4, InsP5, and InsP6 are rapidly formed by several kinds of stimulants in N1E-115 cells.

Transmural pressure inhibits nitric oxide release from human endothelial cells

We examined the effect of transmural pressure on histamine-stimulated nitric oxide release from cultured endothelial cells prepared from human umbilical cord veins. PO2 and pH were kept constant throughout the experiments. Various levels of transmural pressure and atmospheric pressure (40, 80, 120 and 160 mm Hg) were applied. Nitric oxide release was inhibited in a pressure-dependent manner. The inhibitory effects were reversible, and nitric oxide had no effect on the morphology of the cells. Our results suggest that transmural pressure-mediated inhibition of nitric oxide release contributes to pressure-induced vasoconstriction and reduced endothelium-dependent relaxation in patients with hypertension.

[Local recurrence of differentiated thyroid carcinoma effectively treated by local injection of OK-432]

Local recurrence of differentiated thyroid carcinoma in a 67-year-old woman was treated by topical injection of OK-432 every 2-4 weeks. Recurrent tumors turned into small scar-like tissues after 9 months of OK-432 administration. The bleeding from the tumor was well controlled. Secondary recurrent tumors were also effectively treated in the same manner. About 2 years have passed since the start of the treatment and the local recurrence is well controlled. We conclude that topical injection of OK-432 might be a good modality of treatment for the local recurrence of thyroid carcinoma.

Involvement of prostaglandin E2 in ornithine decarboxylase induction by a tumor-promoting agent, 7-bromomethylbenz[a]anthracene, in mouse epidermis

A single topical application of 7-bromomethyl-benz[a]anthracene (BrMBA; 200 nmol) to mouse skin induced epidermal ornithine decarboxylase (ODC) activity. A topical application of indomethacin (1.2 mumol), a cyclooxygenase inhibitor, 10 min before BrMBA application markedly inhibited BrMBA-caused ODC induction. Concurrent application of prostaglandin E2 (PGE2; 0.1-1.5 mumol) reversed the inhibitory effect of indomethacin. Without indomethacin, PGE2 suppressed BrMBA-caused ODC induction. The results indicate that PGE2 has dual actions on the BrMBA-caused ODC induction, i.e. PGE2 plays an essential role in ODC induction caused by BrMBA, whereas exogenous PGE2 rather suppressed BrMBA-caused ODC induction.

New method of investigating functional roles of pressure-sensitive mechanoreceptor in human endothelial cells

The role of pressure-sensitive mechanoreceptors (PSMRs) in histamine-stimulated nitric oxide release from cultured human endothelial cells was investigated, using our new method (helium pack method). PSMRs were stimulated by various levels of pressure applied in addition to atmospheric pressure (40, 80, 120, and 160 mm Hg). Histamine-stimulated nitric oxide release was inhibited in a pressure-dependent manner. Our results suggest that PSMRs modulate nitric oxide release from endothelial cells.

L-arginine as an antihypertensive agent

L-Arginine, the precursor of endothelium-derived relaxing factor (EDRF)/nitric oxide (NO), was administered intravenously in five patients with essential hypertension, one with renovascular hypertension, one with primary aldosteronism, and one with Cushing's syndrome. During the administration, the mean arterial pressure decreased concomitantly with an elevation of cardiac output and a fall in total peripheral resistance in all cases. Indicators of NO release in vivo such as plasma concentrations of L-citrulline and urinary excretion of nitrite/nitrate increased simultaneously during the administration. These results suggest that exogenous L-arginine can produce a vasodilatory effect via stimulating NO release in hypertensives.

Ticlopidine treatment in idiopathic plasmacytic lymphadenopathy with polyclonal hyperimmunoglobulinemia accompanied by nephrotic syndrome

A 36-year-old woman was admitted for idiopathic plasmacytic lymphadenopathy with polyclonal hyperimmunoglobulinemia (IPL) associated with nephrotic syndrome. She was expected to lapse into renal failure because renal biopsy showed focal glomerulosclerosis. VEMP chemotherapy and bolus methyl prednisolone were not effective against excessive urine protein of over 10 g/day. We thus began administration of ticlopidine (6 mg/kg/day), prednisolone (0.4 mg/kg/day) and cyclophosphamide (1 mg/kg/day). After 3 months of this regimen, the urine protein level decreased to less than 0.5 g/day, and renal function was maintained for more than 3 years. It is suggested that ticlopidine is effective for nephropathy complications associated with IPL.