The adaptive role of nitric oxide and hydrogen sulphide in vasoactive responses of thoracic aorta is triggered already in young spontaneously hypertensive rats

Abstract

The aorta plays an important role in blood pressure control so the early determination of its vasoactive properties could predict pathological changes in hypertension. The aim of study was to compare vasoactive properties and geometry of thoracic aorta (TA) and the participation of two vasoactive transmitters, nitric oxide (NO) and hydrogen sulphide (H₂S), in TA tone regulation in young Wistar rats (WR) and spontaneously hypertensive rats (SHR). Four-weeks-old WR and SHR were used. Systolic blood pressure (sBP) was measured by plethysmography. The vasoactivity of TA was evaluated by changes in isometric tension. For morphological study the geometry of TA was measured using light microscopy. Decomposition of NO donor (nitrosoglutathione, GSNO) induced by H₂S donor (Na₂S) was studied by UV-VIS spectroscopy. In SHR the sBP was not increased in spite of cardiac hypertrophy compared to WR. Vasoconstriction to noradrenaline (NA) was decreased in SHR compared to WR which correlated with arterial wall hypotrophy. Acetylcholine (Ach)-induced vasorelaxation was increased and NO component participated in vasorelaxation and basal tone regulation significantly more in SHR. Na₂S induced biphasic effect in both experimental groups, however, the shift towards vasorelaxation was demonstrated in SHR. Pretreatment with NO-synthase inhibitor, N^G-nitro-L-arginine methylester (L-NAME), diminished the contractile part of vasoactive Na₂S effects in both strains, moreover, an increased sensitivity in behalf of vasorelaxation was observed in SHR. Pretreatment with Na₂S did not affect Ach-induced vasorelaxation in WR, but an inhibition was demonstrated in SHR. On the other hand, pretreatment with Na₂S increased the release of NO from GSNO which corresponded with increased GSNO-induced vasorelaxation in both groups. However, this effect was stronger in SHR. The study showed that TA of prehypertensive SHR disposed by decreased contractility and strengthened endothelium-regulated vasorelaxant mechanisms involving of NO and H₂S interaction which could serve as adaptive mechanisms in the adulthood.