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Effect of preventive and regressive isosorbide 5-mononitrate treatment on catecholamine levels in plasma, platelets, adrenals, left ventricle and aorta in cyclosporin A-induced hypertensive rats.

Reis F, Rocha L, Ponte L, Alcobia T, Almeida L, Costa-Almeida C, Teixeira F

Therapeutics Unit, Institute of Pharmacology and Experimental Therapeutics, Medicine Faculty, Coimbra University, 3004-504 Coimbra, Portugal.

Increased vascular reactivity associated with cyclosporin A (CsA)-induced arterial hypertension might result from increased vasoconstriction and/or decreased vasodilatation. The administration of organic NO donors could have beneficial effects by the NO-cGMP reposition, but there is the risk of sympathetic nervous system worsening by neuro-hormonal counter-regulation. We evaluate the effect of preventive and regressive (curative) isosorbide 5-mononitrate (Is-5-Mn) treatment on blood pressures and on plasma, platelets, adrenals, left ventricle and aorta norepinephrine (NE) and epinephrine (E) contents, assessed by HPLC, in CsA-induced hypertensive rats. Five rat groups were tested: control (orange juice), CsA (5 mg/kg/day) and Is-5-Mn (150 mg/kg/day, bid) groups were treated for 7 weeks; preventive group (Is-5-Mn+CsA): Is-5-Mn during 2 weeks plus 7 weeks of Is-5-Mn+CsA; regressive group (CsA+Is-5-Mn): CsA during 7 weeks plus 5 weeks of CsA+Is-5-Mn. The increased BP in the CsA group was prevented, but was not reverted, by concomitant Is-5-Mn treatment. In the CsA-treated rats, there was a noticeable decrease in left ventricle NE and E contents and aorta NE levels and a moderate increase in circulating catecholamines, without significant effect in the adrenals values. When Is-5-Mn was preventively used, the CsA-induced effect on left ventricle and aorta was prevented. Concomitantly, however, the plasma-platelet catecholamine balance was disrupted, accumulating NE in plasma, whereas E increased in aorta, mimic the single Is-5-Mn-treated group. In opposition, in the group used as regressive Is-5-Mn therapy, the adrenals contents were higher compared with the CsA-group and, simultaneously, the CsA-evoked effects on circulating, left ventricle and aorta catecholamines were not reverted. In conclusion, regressive Is-5-Mn therapy was unable to attenuate CsA-induced catecholamine changes and BP values even worsened. On the contrary, preventive Is-5-Mn treatment prevented the catecholamine changes on left ventricle and aorta, but increased plasma NE and aorta E accumulation. Even though with those effects, hypertension development was totally prevented, suggesting that peripheral SNS per se cannot fully explain CsA-induced hypertension. Furthermore, Is-5-Mn might produce beneficial effects only if preventively employed but, considering the changes on peripheral catecholamine contents, a judicious evaluation of the nitrate therapy impact is recommended in order to avoid further deleterious effects.

Published 5 September 2005 in Life Sci, 77(20): 2514-28.
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