PURPOSE: Hypertension may be involved an alteration of intrinsic basal tone in vascular smooth muscle. The purpose of this study was to investigate the vasorelaxant effect of atrial natriuretic peptide (ANP) on isolated non-contracted aorta from two-kidney, one clip (2K1C) renovascular hypertensive rats. METHODS: 2K1C hypertension was induced by clipping the left renal artery and were used 6 weeks later. Age-matched rats receiving a sham treatment, which served as controls. The thoracic aortae were mounted in tissue baths to measure the isometric tension. RESULTS: ANP diminished basal tone in previously unstimulated thoracic aortic rings from 2K1C hypertensive rats, while it had no effect in the control rats. Endothelial destruction potentiated the vasorelaxant effect of ANP on basal tone in 2K1C rats. A similar potentiation of the ANP response was observed by pre-treatment with N omega-nitro-L-arginine methyl ester (L-NAME) or methylene blue in aortic rings with endothelium. Treatment with calcium-free Krebs decreased basal tone and abolished ANPresponse. These effects were observed only in aortic rings from 2K1C rats. Similarly, staurosporine and calphostin C, inhibitors of protein kinase C (PKC), lowered basal tone and abolished ANP-response in hypertensive rats. CONCLUSION: These results demonstrate that ANP has a vasorelaxant effect on basal tone in 2K1C renovascular hypertension. Inhibition of ANP effects on basal tone by calcium-free Krebs and PKC antagonists suggests that altered Ca2+ -active tone is involved in hypertension, that modifies the response of vascular smooth muscle to the ANP.
Animals ; Aorta ; Aorta, Thoracic ; Atrial Natriuretic Factor ; Baths ; Endothelium ; Hypertension ; Hypertension, Renovascular ; Methylene Blue ; Muscle, Smooth, Vascular ; Naphthalenes ; NG-Nitroarginine Methyl Ester ; Placebos ; Protein Kinase C ; Rats ; Renal Artery ; Salicylamides ; Staurosporine

PURPOSE: To evaluate the efficacy of MR cholangiography for follow-up examination after metallic stent placement in the bile duct. MATERIALS AND METHODS: Between December 1999 and June 2000, 15 patients with biliary obstruction in whom metallic biliary stents had been placed underwent MR cholangiography during follow-up examination. The causes of obstruction were hilar cholangiocarcinoma (n=6), common bile duct cancer (n=5), gall bladder cancer (n=1) and pancreatic cancer (n=3). The types of self-expandable metallic stent employed were the nitinol stent (n=2), the Endocoil nitinol stent (n=3), the Ultraflexed Diamond stent (n=5), and the Wallstent (n=5). Using MR cholangiography, we measured the diameter of that part of the biliary stent which showed high signal intensity, assigning one point if this was less than one third of the stent diameter, two points if between one third and two thirds, and three points if more than two thirds. We decided that a higher score indicated fewer artifacts. RESULTS: The score was 1.7-3 (mean, 2.3) points for the Endocoil nitinol stent, 1.7-2.3 (mean, 2) for the nitinot stent, and 1-3 (mean, 1.7) for the Ultraflex Diamond stant. In most cases, two thirds of the stent diameter was observed. For the Wallstent, the score was 1-1.7 (mean, 1.3) points and the inner portion of the stent was almost invisible. CONCLUSION: MR cholangiography is not useful for follow-up examination after the placement of Wallstents and three other types of nitinol stent in the bile duct.
Artifacts ; Bile Ducts* ; Bile* ; Cholangiocarcinoma ; Cholangiography* ; Common Bile Duct ; Diamond ; Follow-Up Studies* ; Gallbladder Neoplasms ; Humans ; Pancreatic Neoplasms ; Stents*

PURPOSE: Thiazide diuretics exert their hypotensive efficacy through a combined vasodilator and diuretic effect. The present study was conducted to assess the inhibitory effect of thiazide diuretic, hydrochlorothiazide, and the thiazide-like diuretics, indapamide and chlorthalidone on contractile responses to norepinephrine and arginine vasopressin in aortic rings from 2K1C renal hypertensive and sham-clipped normotensive rats. METHODS: 2K1C hypertension was made by clipping the left renal artery and age-matched control rats received a sham treatment. Changes in the tension of aortic ring preparations were measured isometrically. RESULTS: Indapamide inhibits the contractile responses to norepinephrine and vasopressin in aortic rings from 2K1C rats, while it did not modify in control rats. The inhibitory effect of indapamide was abolished by endothelium removal. Hydrochlorothiazide or chlorthalidone did not affect the vasoconstriction induced by norepinephrine and vasopressin either in sham or in 2K1C hypertensive rats. CONCLUSION: These results suggest that indapamide inhibits the contractile responses to norepinephrine and vasopressin via an endothelium-dependent mechanism in 2K1C renal hypertension.
Animals ; Aorta ; Arginine Vasopressin ; Chlorthalidone ; Diuretics ; Endothelium ; Hydrochlorothiazide ; Hypertension ; Hypertension, Renal ; Indapamide ; Norepinephrine ; Placebos ; Rats ; Renal Artery ; Salicylamides ; Sodium Chloride Symporter Inhibitors ; Vasoconstriction ; Vasodilation ; Vasopressins

PURPOSE: Evidence has emerged that oxygen-derived free radicals may induce vascular relaxations via ATP-sensitive K+ (K(ATP)) channels and the level of free radicals is increased in animal models of hypertension. The present study was conducted to determine whether relaxations to an K(ATP) channel opener, pinacidil, are increased in the aorta from two-kidney, one clip (2K1C) hypertensive rats and whether free radial scavengers reduce these relaxations. METHODS: 2K1C hypertension was induced by clipping the left renal artery and age-matched control rats received a sham treatment. Rings of aortae without endothelium were suspended for isometric force recording. RESULTS: Relaxations to pinacidil (10(-8) to 10(-5) M), which are abolished by glibenclamide (10(-5) M), were augmented in the aorta from 2K1C rats, compared to those from control rats. In the aorta from 2K1C rats, catalase (1,200 U/mL), but neither superoxide dismutase (150 U/mL) nor deferoxamine (10(-4) M), reduced relaxations to pinacidil, whereas in the aorta from control rats, the free radical scavengers did not affect these relaxations. CONCLUSION: These results suggest that in 2K1C hypertension, vasorelaxation to an KATP channel opener is augmented and that hydrogen peroxide in smooth muscle cells may partly contribute to these relaxations.
Animals ; Aorta ; Catalase ; Deferoxamine ; Endothelium ; Free Radical Scavengers ; Free Radicals ; Glyburide ; Hydrogen Peroxide ; Hypertension ; Hypertension, Renal ; Models, Animal ; Myocytes, Smooth Muscle ; Pinacidil ; Placebos ; Rats ; Relaxation ; Renal Artery ; Salicylamides ; Superoxide Dismutase ; Vasodilation

PURPOSE: Baroreceptor reflex regulation has been shown to reset towards a higher blood pressure level. This study was designed to assess alterations of chronotropic baroreflexes in two-kidney, one clip (2K1C) and deoxycorticosterone acetate (DOCA)-salt hypertensive rats. METHODS: Arterial pressure and heart rate (HR) were monitored continuously during intravenous infusions of phenylephrine or sodium nitroprusside. Ensuing reflex HR responses during each drug infusion were determined in two ways: (a) at 10 s intervals (time analysis), and (b) with every 10 mmHg change in pressure (pressure analysis). RESULTS: Both pressor and depressor responses produced by phenylephrine or sodium nitroprusside were comparable between normotensive and hypertensive rats. Both reflex tachycardia and bradycardia were attenuated in 2K1C hypertensive rats as compared with normotensive rats, whereas no significant differences were shown in DOCA-salt hypertensive rats. CONCLUSION: These results indicate that chronotropic baroreflexes are impaired in 2K1C hypertensive rats, but not in DOCA-salt hypertensive rats.
Animals ; Arterial Pressure ; Baroreflex ; Blood Pressure ; Bradycardia ; Desoxycorticosterone ; Dihydrotachysterol ; Heart Rate ; Hypertension ; Infusions, Intravenous ; Nitroprusside ; Phenylephrine ; Rats ; Reflex ; Tachycardia