Doxazosin protects the expression of endothelial nitric oxide synthase in the endothelium of stroke prone spontaneous hypertensive rats

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AJH–APRIL 2000 –VOL. 13, NO. 4, PART 2

ASH XV ABSTRACTS

but not affected by MTx treatment. Likewise, LV weights were similar in M1, M2, and AS and significantly increased as compared to C (AS:3.4g/kg BW; M1:3.44g/kg; M2:3.45g/ kg; C: 2.15g/kg, n⬍0.01). Plasma IL-6 levels were elevated in AS rats (27 pg/ml vs 17 pg/ml, p⬍0.05) but normalized in MTx treated groups (M1, M2) at all time points studied. Interestingly, the IL-1b and IL-6 levels were increased by more than 30% in the superperfusion solution of myocardium from all groups with aortic banding compared to C (p⬍0.05), but no difference was obtained by MTx compared to AS. Pressure overload LVH in rats is characterized by an increase in plasma levels of IL-6 as well as local myocardial production of IL-6 an IL-1b. 2. Chronic MTx therapy for 8 weeks is sufficient to normalize systemic IL-6 levels, but failed to decrease myocardial production of cytokines and progression of LVH. 3. Different mechanisms may be involved in cardiac and systemic IL-6 production. Key Words: Methotrexate; cytokines; hypertrophy H009 DOXAZOSIN PROTECTS THE EXPRESSION OF ENDOTHELIAL NITRIC OXIDE SYNTHASE IN THE ENDOTHELIUM OF STROKE PRONE SPONTANEOUS HYPERTENSIVE RATS Juan A. Rodriguez-Feo, Marı´a M. Arriero, Ana Jime´nez, Fernando Gonza´lez-Ferna´ndez, Almudena Lo´pez-Blaya, Sandra Velasco, Santos Casado, Antonio Lo´pez-Farre´. Laboratorio de Investigacio´n Cardiovascular e Hipertensio´n. Fundacio´n Jime´nez Diaz. Madrid, Spain Hypertension is associated to an impaired endotheliumdependent nitric oxide vasodilatory response. Nitric oxide is generated by the endothelium through the activity of the endothelial nitric oxide synthase (eNOS). We have recently demonstrated, in cultured endothelial cells, that cytosolic proteins are involved in eNOS mRNA destabilization. The aim of the present study was to analyze the expression of eNOS protein in the vascular wall of stroke prone spontaneous hypertensive rats (SPSHR) and the presence of the cytosolic proteins involved in the modulation of eNOS expression. 13-week-old Wistar Kyoto rats (WKY) and 13week-old SPSHR were used in the study. Compared with WKY, SPSHR showed a reduced expression of eNOS protein in the vascular wall, determined by Western blotting. Immunohistochemistry analysis of the endothelium also showed a decreased expression of eNOS protein in SPSHR. An increased level of cytosolic proteins that bind to the 3⬘-untranslated region (3⬘-UTR) of eNOS mRNA was found in the vascular wall of SPSHR. Treatment of SPSHR with a specific ␣-1 adrenoreceptor antagonist, doxazosin (10 mg/ kg/day) for two weeks, reduced blood pressure an increased eNOS protein expression in the endothelium. This effect was further accompanied by a reduced presence of the cytosolic protein that interacted with 3⬘-UTR of eNOS mRNA. In conclusion, treatment with doxazosin protected eNOS expression in the endothelium of SPSHR. In addition, the present results suggest at least a causal relationship between the presence of the cytosolic protein that interacted with 3⬘-UTR of eNOS mRNA and the level of expression of eNOS protein in the vascular wall.

Key Words: Nitric oxide; doxazosin; hypertension; endothelial nitric oxide synthase H010 ADRENOMEDULLIN DELAYS THE DEVELOPMENT OF PULMONARY HYPERTENSION P. Vijay, T.G. Sharp, and J.W. Brown. Indiana University School of Medicine, Indianapolis, IN Adrenomedullin (ADM), a 52 amino acid peptide with potent vasodilatory and hypotensive action, plays a role in the pathophysiology of pulmonary hypertension (PH). PH is a progressive condition that results in right ventricle failure and death. In this study we evaluated the effect of acute and chronic ADM administration on pulmonary hypertensive rats. Thirty-three Sprague Dawley rats were injected subcutaneously with 60mg/kg monocrotaline (MCT). During the 3-week induction period, group I rats (n ⫽ 11) received no treatment, group II rats (n⫽11) received 30nmol ADM on alternate days and group III rats (n ⫽ 11) received ADM for 3 days at the end of the induction period. Rats from each group were sacrificed either 3 or 6 weeks post MCT treatment. Pulmonary arterial pressures (PAP: mmHg ⫾ SD), endothelin-1 (ET-1: ng/ml), and ADM (pg/ml) were measured at each time point. 3 weeks post MCT

PAP ET-1 ADM

6 weeks post MCT

I (n ⴝ 7)

II (n ⴝ 7)

III (n ⴝ 7)

I (n ⴝ 4)

II (n ⴝ 4)

III (n ⴝ 4)

42 ⫾ 7 4.3 ⫾ 0.5 9.8 ⫾ 0.9

30 ⫾ 6 2.8 ⫾ 0.3 4.3 ⫾ 0.6

22 ⫾ 4 2.3⫾0.5 7.3 ⫾ 0.5

56 ⫾ 12 7.4 ⫾ 1.6 9.3 ⫾ 1.4

40 ⫾ 6 3.6 ⫾ 0.8 6.8 ⫾ 1.1

53 ⫾ 8 5.4 ⫾ 0.9 8.2 ⫾ 0.5

PAP, ET-1 and ADM levels continued to increase between week 3 and 6 in all groups and were maximal in group I. The anti hypertensive effect of acute administration of ADM (group III) was transient. PAP, ET-1, and ADM in these animals were comparable to group I animals by week 6. PAP doubled in group III between 3 and 6 weeks. In contrast, chronic administration of ADM (group II) blunted PH and ET-1 at both time points. PAP, ET-1 and ADM were significantly different in group II vs either group I or group III (pⱕ0.05). These data suggest that ADM may have separate mechanisms of action during acute and chronic administration. The direct vasodilatory effects did not persist beyond the immediate time frame of administration. On the other hand, ADM administered chronically during PH development may affect endothelial cell damage or repair processes, since the effect persists at least three weeks following treatment. Key Words: Adrenomedullin; pulmonary hypertension; endothelin H011 PAGE HYPERTENSION AS A MODEL OF PRESSURE OVERLOAD HYPERTROPHY AND DIASTOLIC DYSFUNCTION J.B. Osborn, C.Y. Teramae, D.M. Meyer, M.M. Redfield. Mayo Clinic, Rochester, MN