Noradrenaline increases intracellular Ca2+ concentration in epithelial cells via α2-adrenoceptors in isolated mouse ileal crypts.

The stimulation of α2-adrenoceptors caused a transient increase of intracellular calcium concentration ([Ca2+]i) monitored by ratiometry using Fura-2 in epithelial cells including enterochromaffin cells in isolated mouse ileal crypts, while stimulation of α1-and ß-adrenoceptors had no effect. The effect of noradrenaline was suppressed by α2-adrenoceptor antagonists, but not by α1-and ß-adrenoceptor antagonists, and partially suppressed by Ni2+ and nicardipine, but not by ω-conotoxin and ω-agatoxin. These results suggest that noradrenaline causes an increase of [Ca2+]i by the influx of extracellular Ca2+ through certain Ca2+ channels via α2-adrenoceptors in epithelial cells of mouse ileal crypts.

Effects of nafamostat mesilate on 5-hydroxytryptamine release from isolated ileal tissues induced by anti-cancer drugs in rats.

Administration of cisplatin and methotrexate significantly increased 5-hydroxytryptamine (5-HT) release from intestinal tissues isolated at 72 h after administration in rats. Daily administration with nafamostat mesilate, a potent serine protease inhibitor, significantly inhibited the release of 5-HT induced by methotrexate, but not by cisplatin, in a dose-dependent manner. When applied to isolated ileal tissues in vitro, nafamostat mesilate also significantly inhibited the release of 5-HT induced by methotrexate, but not by cisplatin, in a concentration-dependent manner. These results suggest that serine proteases are involved in the mechanism of the methotrexate-induced release of 5-HT from the rat small intestine.

5-Hydroxytryptamine induces cyclooxygenase-2 in rat vascular smooth muscle cells: Mechanisms involving Src, PKC and MAPK activation [corrected].

Considering the importance of 5-hydroxytryptamine (5-HT) and cyclooxygenase (COX) products in vascular pathology, we investigated the effects of 5-HT on COX expression in rat vascular smooth muscle cells (VSMCs), and to provide mechanistic insights into these effects. VSMCs were enzymatically isolated from aortic media of Wistar rats. Incubation of VSMCs with 5-HT for 24h stimulated prostaglandin I(2) production, but this stimulation was completely suppressed by NS-398, a selective COX-2 inhibitor. 5-HT induced transient COX-2, but not COX-1, protein and mRNA expression in concentration- and time-dependent manners. This effect of 5-HT was completely inhibited by sarpogrelate, a 5-HT(2A) receptor antagonist. 5-HT-induced COX-2 expression was markedly blunted by Ca(2+) depletion; GF 109203X, a protein kinase C (PKC) inhibitor; PP2, an inhibitor of Src-family tyrosine kinase (Src); PD 98059, an inhibitor of extracellular signal-regulated kinase (ERK) activation; SB 203580, an inhibitor of p38 mitogen-activated protein kinase (MAPK); and SP 600125, an inhibitor of c-Jun N-terminal kinase (JNK). 5-HT activated ERK and p38 MAPK, followed by JNK activation. PP2 inhibited these activations, while GF 109203X inhibited only JNK activation. Furthermore, PD 98059 inhibited JNK activation. These results suggest that 5-HT induces COX-2 expression in rat VSMCs, and that PKC, Src, and MAPK activation are each essential for the full expression of COX-2 pathways.

Anti-inflammatory drugs ameliorate opposite enzymatic changes in ileal 5-hydroxytryptamine metabolism in the delayed phase after cisplatin administration to rats.

The effects of anti-inflammatory drugs on ileal 5-hydroxytryptamine (5-HT) metabolic dynamics at 72 h after a single administration of cisplatin were investigated in rats. Cisplatin 5 mg/kg i.p. caused pathological changes, with an inflammatory response occurring 72 h after its administration. The inflammatory response was associated with the induction of cyclooxygenase-2, but not cyclooxygenase-1, in the ileal mucosa at 72 h after the cisplatin administration. Daily treatment with meloxicam 3 mg/kg s.c. ameliorated the cisplatin-induced mucosal damage, whereas dexamethasone 1 mg/kg s.c. did not. Cisplatin administration also caused a significant increase in cyclooxygenase-2 mRNA expression at 72 h after administration, which was blunted by dexamethasone, but not by meloxicam. Cisplatin increased the content of 5-HT and its metabolite, 5-hydroxyindoleacetic acid (5-HIAA), but had no effect on 5-HT turnover (5-HIAA/5-HT ratio). Meloxicam and dexamethasone did not significantly decrease 5-HT and 5-HIAA content. Cisplatin significantly decreased monoamine oxidase activity but increased tryptophan hydroxylase (TPH) activity and TPH(1) mRNA expression in ileal tissue. Meloxicam and dexamethasone significantly restored the decreased monoamine oxidase activity and inhibited the cisplatin-induced increase in tryptophan hydroxylase activity toward the control levels. These drugs also decreased the cisplatin-induced increase in TPH(1) mRNA expression. Neither cisplatin nor the anti-inflammatory drugs had significant effect on mRNA expression of the serotonin re-uptake transporter. These results suggest that the inflammatory response associated with cyclooxygenase-2 induction is involved in the opposite change in ileal tryptophan hydroxylase and monoamine oxidase activities in the delayed phase after single administration of cisplatin to rats.

Sphingosine 1-phosphate inhibits nitric oxide production induced by interleukin-1beta in rat vascular smooth muscle cells.

Sphingosine 1-phosphate (S1P) is a lipid mediator that exerts potent and diverse biological effects on several cardiovascular cells. We investigated the effect of S1P on interleukin (IL)-1beta-induced nitric oxide (NO) production and inducible NO synthase (iNOS) expression in rat vascular smooth muscle cells (VSMCs). S1P inhibited NO production at concentrations higher than 0.1 muM; this was associated with the inhibition of iNOS protein and mRNA expression. S1P also inhibited IL-1beta-induced GTP cyclohydrolase I (GTPCH) mRNA expression. Pertussis toxin (PTX) partially attenuated the inhibitory effects of S1P on NO production and iNOS protein induction, whereas it completely blocked the inhibitory effects on iNOS and GTPCH mRNA expression. S1P inhibited iNOS expression in Ca(2+)-depleted conditions; PTX did not modify this effect. The Rho kinase inhibitor Y 27632 partially but significantly attenuated the inhibitory effect of S1P on iNOS expression in Ca(2+)-depleted condition but did not affect it in the presence of Ca(2+). S1P significantly inhibited IL-1beta-induced persistent activation of extracellular signal-regulated kinase (ERK) but had no effect in Ca(2+)-depleted conditions. Thus, S1P inhibits IL-1beta induction of NO production and iNOS expression in rat VSMCs through multiple mechanisms involving both PTX-sensitive and -insensitive G proteins coupled to S1P receptors. Furthermore, Ca(2+)-dependent ERK inhibition and Ca(2+)-independent Rho kinase activation might be involved in the inhibitory mechanism of iNOS expression. Through its action on NO production by VSMCs, S1P may play an important role in the progression of local vascular injury associated with thrombosis, atherosclerosis, and hypertension.

Sphingosine 1-phosphate induces cyclooxygenase-2 via Ca2+-dependent, but MAPK-independent mechanism in rat vascular smooth muscle cells.

The effects of sphingosine 1-phosphate (S1P) on prostaglandin I(2) (PGI(2)) production and cyclooxygenase (COX) expression in cultured rat vascular smooth muscle cells (VSMCs) were investigated. S1P stimulated PGI(2) production in a concentration-dependent manner, which was completely suppressed by NS-398, a selective COX-2 inhibitor, as determined by radioimmunoassay. S1P stimulated COX-2 protein and mRNA expressions in a concentration- and time-dependent manner, while it had no effect on COX-1 expression. S1P(2) and S1P(3) receptors mRNA were abundantly expressed in rat VSMCs. Suramin, an antagonist of S1P(3) receptor, almost completely inhibited S1P-induced COX-2 expression. Pretreatment of VSMCs with pertussis toxin (PTX) partially, but significantly inhibited S1P-induced PGI(2) production and COX-2 expression. S1P also activated extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK). However, neither PD 98059, a selective inhibitor of ERK activation, nor SB 203580, a selective inhibitor of p38 MAPK, had a significant inhibitory effect on S1P-induced COX-2 expression, suggesting that the MAPK activation does not play main roles in S1P-induced COX-2 induction. S1P-induced COX-2 expression was inhibited by PP2, an inhibitor of Src-family tyrosine kinase, Ca(2+) depletion, and GF 109203X, an inhibitor of protein kinase C (PKC). These results suggest that S1P stimulates COX-2 induction in rat VSMCs through mechanisms involving Ca(2+)-dependent PKC and Src-family tyrosine kinase activation via S1P(3) receptor coupled to PTX-sensitive and -insensitive G proteins.

Docosahexaenoic acid enhances cyclooxygenase-2 induction by facilitating p44/42, but not p38, mitogen-activated protein kinase activation in rat vascular smooth muscle cells.

The effect of docosahexaenoic acid (DHA) on cyclooxygenase expression induced by interleukin (IL)-1beta and phorbol 12-myristate 13-acetate (PMA) in rat vascular smooth muscle cells (VSMCs) was investigated in order to clarify the cellular mechanism of cardiovascular protective effects. DHA and eicosapentaenoic acid slightly enhanced IL-1beta-induced cyclooxygenase (COX)-2, but not COX-1, expression, whereas arachidonic acid had no effect. DHA also slightly enhanced PMA-induced COX-2 expression. DHA stimulated both rapid and prolonged activation of p44/42, but not p38, mitogen-activated protein kinase (MAPK) induced by IL-1beta and PMA. These results suggest that DHA enhances the COX-2 expression by selectively facilitating p44/42 MAPK activation in VSMCs.

[Serotonin and anticancer drug-induced emesis].

Cytotoxic drug-induced nausea and vomiting are the side effects most feared by cancer patients. Emesis is an instinctive defense reaction caused by the somato-autonomic nerve reflex, which is integrated in the medulla oblongata. Emesis caused by anticancer drugs is associated with an increase in the concentration of serotonin (5-HT) (5-HT) in the intestinal mucosa and brainstem. 5-HT released from the enterochromaffin (EC) cells, which synthesize and secrete 5-HT, stimulates the 5-HT receptors on the adjacent vagal afferent nerves. The depolarization of the vagal afferent nerves stimulates the vomiting center in the brainstem and eventually induces a vomiting reflex. 5-HT released from EC cells appears to mediate the cisplatin-induced emesis sensitive to 5-HT(3) receptor antagonists. The precise role of 5-HT in the occurrence of vomiting has not been fully elucidated. The present review describes the role of 5-HT in anticancer drug-induced emesis from the viewpoint of 5-HT release and afferent vagal nerve activity. Various models and methods for predicting emesis are also evaluated.

Cardiovascular protective effects of n-3 polyunsaturated fatty acids with special emphasis on docosahexaenoic acid.

It is widely accepted that n-3 polyunsaturated fatty acids (PUFAs) rich in fish oils protect against several types of cardiovascular diseases such as myocardial infarction, arrhythmia, atherosclerosis, or hypertension. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may be the active biological components of these effects. Although the precise cellular and molecular mechanisms underlying the beneficial effects are still uncertain, the protective effects of n-3 PUFAs are attributable to their direct effects on vascular smooth muscle cell (VSMC) functions. These n-3 PUFAs activate K(+)(ATP) channels and inhibit certain types of Ca(2+) channels, probably via at least 2 distinct mechanisms. N-3 PUFAs favorably alter the eicosanoid profile and regulate cytokine-induced expression of inducible nitric oxide synthase and cyclooxygenase-2 via mechanisms involving modulation of signaling transduction events. N-3 PUFAs also modulate VSMC proliferation, migration, and apoptosis. These recent data suggest that modulation of these VSMC functions contribute to the beneficial effects of n-3 PUFAs on various cardiovascular disorders. Furthermore, recent studies strongly suggest that DHA has more potent and beneficial effects than EPA. However, many questions about the cellular and molecular mechanisms still remain to be answered.

Pharmacological aspects of anticancer drug-induced emesis with emphasis on serotonin release and vagal nerve activity.

Cytotoxic drug-induced nausea and vomiting are the side effects most feared by cancer patients. Emesis is an instinctive defense reaction caused by the somatoautonomic nerve reflex, which is integrated in the medulla oblongata. Emesis caused by cytotoxic drugs such as cisplatin is associated with an increase in the concentration of 5-hydroxytryptamine (5-HT) in the intestine and the brainstem. It is proposed that cytotoxic drugs evoke 5-HT release from the enterochromaffin (EC) cells in the intestinal mucosa and that the released 5-HT stimulates the 5-HT receptors on the adjacent vagal afferent nerves. The depolarization of the vagal afferent nerves stimulates the vomiting center in the brainstem and eventually induces a vomiting reflex. 5-HT released from EC cells seems to mediate the cisplatin-induced emesis sensitive to 5-HT(3) receptor antagonists. The release of 5-HT from the EC cells, however, is regulated by polymodal mechanisms on autoreceptors or heteroreceptors. The precise role of 5-HT on the occurrence of vomiting has not been fully elucidated. The present review aims to describe the role of 5-HT in anticancer drug-induced emesis from the viewpoint of 5-HT release and afferent vagus nerve activity. Various methods for predicting emesis are also evaluated.

Granisetron: is there a dose-response effect on nausea and vomiting?

PURPOSE: Nausea and vomiting are two of the most debilitating side effects of cytotoxic chemotherapy. Prevention of nausea and vomiting is, thus, very important to ensure that cancer patients continue to receive optimal cytotoxic therapy while seeking to maintain their quality of life. Significant advances in antiemetic therapy have been achieved since the introduction of the 5-HT(3) receptor antagonists, and these agents are currently regarded as first-line antiemetic agents. The aim of this article is to examine the hypothesis that there is a dose-response effect of granisetron for preventing chemotherapy-induced nausea and vomiting in cancer patients. METHODS: A literature review of relevant publications was undertaken to provide a comprehensive review of issues related to the control of chemotherapy-induced emesis with escalating doses of granisetron. RESULTS: There is evidence to suggest that there is a significant trend towards an improved efficacy of granisetron-in both the control of emesis and secondary end-points such as nausea and anorexia-with increasing doses, up to 40 micro g/kg, in adults. At this dose, the likelihood of treatment success may be enhanced for most patients regardless of their individual emetogenic risk. Additionally, incremental doses of granisetron (up to 9 mg) have been shown to be effective and well tolerated in patients with refractory emesis. CONCLUSIONS: Those patients experiencing inadequate control of nausea and vomiting following granisetron may also benefit from retreatment with supplementary doses of granisetron, and over subsequent chemotherapy cycles, these patients should receive granisetron 40 micro g/kg to ensure emesis protection.

[A new vomiting animal model--mink].

AIM: To establish a new, reliable vomiting model in minks. METHODS: Adult male minks (Mustela vison) were randomly divided into groups (n = 6). Cisplatin, apomorphine, copper sulfate and X-radiation were used to establish vomiting model. Retching and vomiting were observed after the vomiting models were given anti-vomiting agents. After the behavioral experiment, assay of 5-HT in the ileum was performed by immunohistologic method. RESULTS: Cisplatin 7.5 mg.kg-1 i.p., apomorphine 1.6 mg.kg-1 s.c. and copper sulfate 40 mg.kg-1 ig were shown to evoke vomiting. Retching and vomiting were significantly inhibited in ondansetron and metoclopramide pretreated minks (P < 0.05, P < 0.01). CONCLUSION: As a new vomiting model, minks may be of great value in studying vomiting mechanism and screening new antiemetic drugs.

Combination therapy with granisetron, methylprednisolone and droperidol as an antiemetic prophylaxis in CDDP-induced delayed emesis for gynecologic cancer.

OBJECTIVE: To better control both acute and delayed emesis resulting from cisplatin(CDDP)-based chemotherapy for gynecological malignancies, we designed a 'cocktail therapy' (CCT) using granisetron (GRN) in combination with methylprednisolone (MPD) plus droperidol (DRP). METHODS: Two crossover clinical trials were carried out to compare the efficacy and safety of (a) GRN alone (3 mg/patient) with that of GRN, MPD (250 mg/patient) and DRP (0.5 ml/patient) in 42 patients (CCT group) and (b) GRN and MPD (CMB group) with that of the CCT group in 27 patients during the first 7 days of chemotherapy, independent of the weight/body surface of the patients. One of these regimens was administered intravenously for the first 3 days of chemotherapy, in case of failure for a maximum of 5 days. RESULTS: For acute emesis, complete protection from nausea and vomiting by the end of the 1st day was achieved in 64.3% receiving GRN and in 92.9% receiving CCT (p < 0.01). For delayed emesis, complete protection was best achieved in CCT on days 2-3, showing statistical significance compared to GRN treatment (p < 0.01). Comparing the three kinds of treatment during 7 days, the lowest protection was 38.1% in the GRN group, 51.9% in the CMB group and 72.5% in the CCT group, especially on days 2 or 3. CONCLUSIONS: The CCT combination is useful for the control of delayed and/or anticipatory emesis resulting from CDDP-based chemotherapy for women with gynecological malignancies.

Isatin, an endogenous MAO inhibitor, improves bradykinesia and dopamine levels in a rat model of Parkinson's disease induced by Japanese encephalitis virus.

Isatin, an endogenous monoamine oxidase (MAO) inhibitor, has an important role in the control of neurotransmitter concentration. We previously reported that exogenously administered isatin significantly increased acetylcholine (ACh) and dopamine (DA) levels in the rat striatum. In order to test the possibility of treating Parkinson's disease by isatin, we evaluated DA levels in the striatum and bradykinesia using a rat model of Parkinson's disease induced by the Japanese encephalitis virus (JEV).We have already reported that in adult Fischer rats infected with JEV at day 13, there was a marked decrease of tyrosine hydroxylase-positive neurons in the bilateral substantia nigra after 12 weeks. Effects of isatin were investigated in JEV-induced post-encephalitic parkinsonism rats by a pole test and high performance liquid chromatograph (HPLC) with an electrochemical detector (ECD). Isatin (100 mg/kg per day for 1 week, intraperitoneal injection) improved the bradykinesia observed in the JEV-induced parkinsonism rats. Dopamine (DA) concentrations in the JEV-infected rats were profoundly reduced in the striatum as compared with controls. Isatin also increased DA in the striatum of parkinsonism rats. These results suggest that isatin could be a possible treatment for Parkinson's disease as well as for post-encephalitic parkinsonism.

5-hydroxytryptamine (5-HT) concentrations in the hippocampus, the hypothalamus and the medulla oblongata related to cisplatin-induced pica of rats.

We previously reported that the concentration of 5-hydroxytryptamine (5-HT) in the brainstem of cisplatin-administered ferrets is significantly increased as compared with that of control animals. In an attempt to clarify the mechanisms of emesis induced by cytotoxic drugs, we measured kaolin ingestion (pica) and the tissue concentrations of 5-HT, norepinephrine (NE) and dopamine in various brain regions of rats after cisplatin administration. 5-HT concentrations in the hippocampus, the medulla oblongata and the hypothalamus significantly increased 72 hours after a single dose administration of cisplatin (5 mg/kg, i.p.) compared with those of control rats. NE concentration in the hippocampus significantly increased simultaneously with kaolin ingestion in cisplatin-treated rats. These results suggest that higher brain regions such as the hippocampus and the hypothalamus are involved in cisplatin-induced emesis.

Effects of fluvoxamine, a selective serotonin re-uptake inhibitor, on serotonin release from the mouse isolated ileum.

The presence of nausea and vomiting is problematic for all selective serotonin re-uptake inhibitors (SSRIs), and their usefulness as anti-depressants is limited in this respect. In an attempt to examine the background of SSRI-induced emesis, the present study aims to describe the role of 5-hydroxytryptamine (serotonin:5-HT) from the viewpoint of 5-HT release in the mouse-isolated ileum. In this study, it was demonstrated that 5-HT release from the mouse-isolated ileum was significantly increased by fluvoxamine at a concentration of 10(-6) M. Also, it was demonstrated that granisetron, a 5-HT3 receptor antagonist, inhibited significantly the increase in fluvoxamine (10(-6) M) -induced 5-HT release. The effect of granisetron on fluvoxamine-induced 5-HT release was occurred in a concentration-dependent manner. The present study demonstrated for the first time that the SSRI-induced increase in 5-HT release from the isolated ileum was significantly inhibited by 5-HT3 receptor antagonist. These results suggest that 5-HT3 receptors might be involved in SSRI-induced 5-HT release from the mouse isolated ileal tissue. Fluvoxamine (10(-6) M)-induced 5-HT release was inhibited concentration -dependently by the concomitant perfusion of diltiazem. The results suggest that L-type calcium channel might be also involved in SSRI-induced 5-HT release from the isolated ileum. Furthermore, tetrodotoxin (10(-6) M) completely inhibited the increase in 5-HT release induced by fluvoxamine. This finding suggests that the increase of 5-HT induced by fluvoxamine involves enterochromaffin (EC) cell stimulation via an inter-neuron pathway in the gastrointestinal tract (GI). SSRI initiates an increase in the concentration of 5-HT in the GI tract. 5-HT released from the EC cells of the intestinal mucosa may stimulate the 5-HT3 receptors on vagal afferent nerve fibers. This depolarization of vagal afferents may result in a 5-HT increase in the brainstem and, thus, lead to emesis.

[Modulation of sphingosine 1-phosphate, a new lipid mediator, on nitric oxide production by vascular smooth muscle cells].

The effects of sphingosine 1-phosphate (S1P) on nitric oxide (NO) production induced by interleukin (IL)-1 beta in cultured rat vascular smooth muscle cells (VSMCs) have been investigated. Rat VSMCs abundantly expressed mRNA of Edg-3 and Edg-5 receptor subtypes in both unstimulated and IL-1 beta-stimulated cells. S1P at higher than 0.1 microM inhibited the NO production induced by IL-1 beta in a concentration-dependent manner, in which S1P at 10 microM caused over 90% inhibition. S1P also inhibited inducible NO synthase (iNOS) protein and mRNA expressions induced by IL-1 beta in a concentration-dependent manner, which effects were smaller than that in the NO production. S1P also significantly inhibited GTP cyclohydrolase I (GTPCH) mRNA expression induced by IL-1 beta. PTX pretreatment partially prevented the inhibitory effects of S1P on the NO production and iNOS induction, while completely prevented the inhibitory effects on iNOS and GTPCH mRNA expressions. In PTX-pretreated VSMC, S1P showed a bell-shaped enhancing and inhibitory effect on iNOS protein expression. These results suggest that S1P modulates IL-1 beta induction of NO production by rat VSMCs through multiple mechanisms, partially via Edg-3 and Edg-5 receptor subtypes coupled to PTX-sensitive G proteins.

Docosahexaenoic acid potentiates interleukin-1beta induction of nitric oxide synthase through mechanism involving p44/42 MAPK activation in rat vascular smooth muscle cells.

The effect of docosahexaenoic acid (DHA) on nitric oxide (NO) production and inducible NO synthase (iNOS) expression induced by interleukin (IL)-1beta, and whether the effect of DHA is related to its effect on mitogen-activated protein kinase (MAPK) activation were investigated in cultured rat vascular smooth muscle cells (VSMCs). DHA and eicosapentaenoic acid (EPA), although less potent, increased the NO production induced by IL-1beta (3 ng ml(-1)) in a concentration-dependent manner (3 - 30 microM) Arachidonic acid had no significant effect. The stimulatory effect of DHA (30 microM) on the NO production was more obvious at lower concentrations of IL-1beta. IL-1beta induced iNOS protein and mRNA expressions, which were significantly potentiated by DHA. EPA (30 microM) had a tendency to increase the iNOS protein and mRNA expressions, but arachidonic acid had no effect. IL-1beta-induced iNOS protein expression was significantly inhibited by PD 98059 (10 microM), a selective inhibitor of p44/42 MAPK kinase, both in the absence and the presence of DHA. SB 203580 (10 microM), a selective inhibitor of p38 MAPK activity, had no significant effect, although had a tendency to inhibit slightly. IL-1beta increased the phosphorylation of p44/42 MAPK, while it did not apparently increase the phosphorylation of p38 MAPK. DHA significantly potentiated the IL-1beta-induced phosphorylation of p44/42 MAPK, while it had no significant effect on the phosphorylation of p38 MAPK. These results suggest that DHA increases NO production by potentiating iNOS expression induced by IL-1beta through mechanism involving p44/42 MAPK signalling cascade in rat VSMCs. The present study may contribute to the understanding of basic mechanisms underlying the beneficial effects of DHA on various cardiovascular disorders.

Reduced expressions of inducible nitric oxide synthase and cyclooxygenase-2 in vascular smooth muscle cells of stroke-prone spontaneously hypertensive rats.

Inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 are expressed in vascular smooth muscle cells stimulated with interleukin-1beta (IL-1beta), resulting in the production of nitric oxide (NO) and prostaglandins (PGs) such as PGI2. The iNOS and COX-2 proteins and their mRNA expressions in cultured vascular smooth muscle cells isolated from 6-7 week-old stroke-prone spontaneously hypertensive rats (SHRSP) were compared with those in the cells isolated from age-matched normotensive Wistar Kyoto rats (WKY). The IL-1beta-induced NO production and iNOS expression in vascular smooth muscle cells of SHRSP were significantly lower than those in cells of WKY. Similarly, PGI2 production and COX-2 expression were significantly lower in vascular smooth muscle cells of SHRSP than WKY, whereas there was no difference in the COX-1 expression. There were no significant differences in iNOS and COX-2 mRNA expressions between the two strains, suggesting that these protein expression may be reduced at the post-transcriptional level in cells of SHRSP. These results further suggest that the reduction of iNOS and COX-2 expressions in vascular smooth muscle cells may have relevance to the pathophysiology in SHRSP.

Effects of granisetron, a 5-HT3 receptor antagonist, on 5-hydroxytryptamine (5-HT) release from the isolated ileum in a delayed-emesis rat model.

We examined the effects of granisetron, a 5-HT3-receptor antagonist, on the release of serotonin (5-hydroxytryptamine, 5-HT) from the isolated ileum and on histopathological changes of the intestine in a delayed-emesis rat model. The rats were studied 72 hours after receiving an intraperitoneal (i.p.) dose of cisplatin (5 mg/kg). The 5-HT content in the isolated ileum 72 hours after administration was significantly higher in the cisplatin group (26.0 +/- 3.0 ng/mg protein, p < 0.001) than in the non-drug control group (9.6 +/- 0.6 ng/mg protein). The increase in 5-HT content in the cisplatin group was significantly inhibited in rats pretreated with granisetron (17.5 +/- 2.2 ng/mg protein, p < 0.05). The release of 5-HT from the isolated ileum was significantly greater in the cisplatin group (11,963.0 +/- 2,104.6 ng x hr/g tissue, p < 0.01) than in the non-drug control group (2,861.0 +/- 210.7 ng x hr/g tissue). The increased 5-HT release from the isolated ileum in the cisplatin group was significantly inhibited in rats pretreated with granisetron (3,359.8 +/- 494.3 ng x hr/g tissue, p < 0.01). Disarrangement of intestinal villi, luminal dilatation of crypts and decreased numbers of goblet cells were observed in the cisplatin group. The group pretreated with granisetron showed mild macroscopic and histopathological changes, but no significant weight loss. The histopathological changes of the intestinal mucosa were apparently associated with the release of 5-HT. Our results suggest that 5-HT release from the enterochromaffin cells, accompanied by histopathological changes of the intestinal mucosa, is involved in the onset of delayed emesis after administration of cisplatin. These findings suggest that treatment with granisetron before the administration of anticancer drugs may prevent delayed emesis and intestinal disturbances associated with anticancer drugs.