We have examined whether expression of angiotensin II (Ang II) type 1 (AT 1 ) and/or type 2 (AT 2 ) receptors are changed in thoracic aorta under pressure-overload by abdominal aortic banding in rats and determined whether their changes are accompanied by alteration in contractile response of thoracic aorta to Ang II. AT 2 receptor mRNA levels determined by reverse transcription-polymerase chain reaction or quantitative real-time polymerase chain reaction were increased by about 300% in aortas 4, 7, 14, and 28 days after banding without changes in AT 1 receptor mRNA levels. Contractile response of aortic rings to Ang II was decreased in thoracic aortas 7 days after banding, and AT 2 receptor antagonist PD123319 (1-[[4-(dimethulamino)-3-methylphenyl]methyl]-5-(diphenylacetyl)-4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid ditrifluoroacetate) (10 Ϫ6 M) increased the Ang II responsiveness in pressure-loaded but not in sham rings. After removal of the endothelium or treatment with N G -nitro-L-arginine methyl ester (L-NAME), no differences were observed in Ang II responsiveness between sham and pressure-loaded rings. Either losartan (1 mg/kg/day i.p.) or candesartan (2 mg/kg/day p.o.) for 7 days after banding not only abolished the up-regulation of AT 2 receptor mRNA in aortas but also recovered their Ang II responsiveness. Basal cGMP levels were 2 times higher in pressureloaded than in sham rings; both levels were not affected by Ang II (10 Ϫ7 M; 5 min), but greatly decreased by L-NAME (10 Ϫ4 M, 30 min). These results suggest that pressure-overload induces the up-regulation of AT 2 receptor expression in aortas via AT 1 receptor and thereby negatively modulates the vasoconstrictor sensitivity to Ang II, probably mediated by the mechanisms independent of the nitric oxide-cGMP system.

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1 Cyclic guanosine monophosphate (cyclic GMP)-mediated mechanism plays an important role in vasodilatation and blood pressure regulation. We investigated the e ects of high salt intake on the nitric oxide (NO) ± cyclic GMP signal transduction pathway regulating relaxation in aortas of spontaneously hypertensive rats (SHR). 2 Four-week-old SHR and normotensive Wistar-Kyoto rats (WKY) received a normal salt diet (0.3% NaCl) or a high salt diet (8% NaCl) for 4 weeks. 3 In aortic rings from SHR, endothelium-dependent relaxations in response to acetylcholine (ACh), adenosine diphosphate (ADP) and calcium ionophore A23187 were signi®cantly impaired by the high salt intake. The endothelium-independent relaxations in response to sodium nitroprusside (SNP) and nitroglycerin were also impaired, but that to 8-bromo-cyclic GMP remained unchanged. On the other hand, high salt diet had no signi®cant e ects on the relaxations of aortic rings from WKY. 4 In aortas from SHR, the release of NO stimulated by ACh was signi®cantly enhanced, whereas the production of cyclic GMP induced by either ACh or SNP was decreased by the high salt intake. 5 Western blot analysis showed that the protein level of endothelial NO synthase (eNOS) was slightly increased, whereas that of soluble guanylate cyclase (sGC) was dramatically reduced by the high salt intake. 6 These results indicate that in SHR, excessive dietary salt can result in downregulation of sGC followed by decreased cyclic GMP production, which leads to impairment of vascular relaxation in responses to NO. It is notable that chronic high salt intake impairs the sGC/cyclic GMP pathway but not the eNOS/NO pathway.

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1. The antitumour effect of orally administered cordycepin, a component isolated from water extracts of Cordyceps sinensis, was examined in mice inoculated with B16 melanoma (B16-BL6) cells. 2. B16-BL6 (1 x 10(6)) cells were inoculated subcutaneously into the right footpad of mice. At 2 weeks after the cell inoculation, the enlarged primary tumour lump was weighed. Cordycepin (0, 5 and 15 mg/kg per day) was administered orally to the mice for 2 weeks from the date of tumour inoculation. Cordycepin (15 mg/kg per day) significantly reduced by 36% the wet weight of the primary tumour lump compared to that of the untreated control mice, without any loss of bodyweight or systemic toxicity. 3. Cordycepin (15 mg/kg per day) administered orally for 2 weeks inhibited the tumour enlargement in the right thigh inoculated with B16-BL6 cells premixed with extracellular matrix (Matrigel). 4. These results indicate that orally administered cordycepin inhibits melanoma cell growth in mice with no adverse effects.

Generally, blood pressure (BP) in rats and mice is measured using the tail-cuff method after heating the animal. However, this method yields an indirect measurement of BP, and the requirement for animal heating and restraint may cause stress-induced changes in BP. [1][2][3][4] To overcome these limitations, a radiotelemetric monitoring system was developed to continuously measure cardiovascular parameters in freely moving rats.5) Bazil et al. 6) compared the cardiovascular parameters of spontaneously hypertensive rats (SHR) recorded by different methods (e.g., radiotelemetry device, cannulated arterial catheters, and indirect tail-cuff) and suggested that telemetric monitoring was a useful method of cardiovascular study that did not cause stress-induced changes in blood pressure. However, telemetric monitoring requires the implantation of a radiotransmitter in the abdomen, and the apparatus is expensive.Recently, a novel device was developed for the tail-cuff method that does not require animal heating if the ambient temperature is greater than 23°C. The goal of this study was to assess the validity of this novel tail-cuff method without animal heating (method A) when compared with the conventional heating tail-cuff method (method B; unanesthetized rats with heating), telemetry method (method C; unanesthetized restrained rats without heating), or carotid arterial catheter method (method D; anesthetized rats, carotid arterial cannulation). MATERIALS AND METHODS Animals and Operative ProceduresExperiments were performed in accordance with the Guiding Principles for the Care and Use of Laboratory Animals approved by the Japanese Pharmacological Society and Mukogawa Women's University. Male rats at 11-12 weeks of age were used, and BP and heart rate (HR) were always measured between 13:00-17:00 h.Tail-Cuff Method without Heating (Method A) Rats (SHR/Izm, Japan SLC, Inc., Shizuoka, Japan) were placed in plastic restrainers. A cuff with a pneumatic pulse sensor was attached to the tail. Rats were allowed to habituate to this procedure for 7 d before experiments were performed. BP and HR values were recorded on a Model MK-2000 (Muromachi Kikai Co., Ltd., Tokyo, Japan) without heating and were averaged from at least three consecutive readings obtained from each rat.Tail-Cuff Method with Heating (Method B) In this experiment, we measured the blood pressure and heart rate of rats used in the experiment of method A. Rats were preheated in a chamber at 35°C for 10 min, then placed in plastic restrainers. A cuff with a pneumatic pulse sensor was attached to the tail. Rats were allowed to habituate to this procedure for 7 d before experiments were performed. BP and HR values were recorded on a Model MK-2000 with heating and were averaged from at least three consecutive readings obtained from each rat.Telemetry Method (Method C) Rats (SHR/NCrj, Charles River Japan, Yokohama, Japan) were implanted with a radio transmitter (TA11PA-C40, Data Sciences, St. Paul, MN, U.S.A.). Individual rats were placed in a plastic cage on top o...

BACKGROUND AND PURPOSEIn non-obese diabetic animals, protease-activated receptor-2 (PAR2) agonists are more effective vasodilators, which is attributed to increased COX-2 and endothelial NOS (eNOS) activities. Under conditions of diabetes and obesity, the effectiveness of PAR2 agonists is unknown. We compared the vasodilator responses of small calibre mesenteric arteries from obese diabetic B6.BKS(D)-Leprdb/J (db/db) induced by PAR2-activating agonists 2-furoyl-LIGRLO-amide (2fly) and trypsin to those obtained in controls [C57BL/6J (C57)], and assessed the contributions of COX, NOS and calcium-activated potassium channels (KCa) to these responses.EXPERIMENTAL APPROACHArteries mounted in wire myographs under isometric tension conditions were contracted submaximally by U46619 then exposed to vasodilators. mRNA and protein expression of PAR2, eNOS and soluble GC (sGC) were determined by real-time PCR and Western blots.KEY RESULTSACh- and nitroprusside-induced relaxations were attenuated in db/db compared with C57. In contrast, 2fly- and trypsin-induced relaxations were largely retained in db/db. A NOS inhibitor partly inhibited ACh- and 2fly-induced relaxations in C57, but not those in db/db. Inhibitors of the COX-cAMP pathway (FR122044, SC560, NS398, SC58125, SQ22536, CAY10441) did not affect these relaxation responses in either strain. Charybdotoxin (BKCa, SK3.1 blocker), but not iberiotoxin (BKCa blocker), inhibited responses to the PAR2 agonists in db/db. In db/db protein levels of eNOS were higher, whereas those of sGC were lower than in C57. PAR2 mRNA expression in db/db was higher than in C57.CONCLUSIONS AND IMPLICATIONSPAR2-mediated vasodilatation is protected against the negative effects of obesity and diabetes in mice. In diabetic vascular dysfunction, preserved PAR2 vasodilatation was linked to activation of SK3.1.