Cardiology Letters 2015, 24(3):141-149

Functional and structural pattern of conduit arteries in two models of experimental hypertension

Drobná M, Kristek F, Török J

Ústav normálnej a patologickej fyziológie, Slovenská akadémia vied v Bratislave, Slovenská republika

Aim: The aim of the study was to compare reactivity and structural alterations in thoracic aorta and carotid artery in two different animal models of hypertension NO-deficient and spontaneous hypertensive rats (SHR).

Methods: Three groups of animals were used: 1) control normotensive Wistar rats, 2) NO-deficient rats (Wistar rats treated for 6 weeks with NO-synthase inhibitor, NG-nitro-L-arginíne methylester - L-NAME), and 3) SHR. The experiment lasted from the 10th to the 16th week of the animals´ age. At the end of the experiment functional and morphological investigations were performed. For functional study isolated rings from thoracic aorta and carotid artery were used and relaxation resposes to increasing doses of acetylcholine (1 nmol/l - 10 µmol/l) after precontraction with submaximal dose of phenylephrine (1µM) were monitored. For morphological study the same arteries were processed after perfusion fixation under the pressure 120 mm Hg according to standard electron microscopy procedure. The geometry of the arteries: inner diameter, wall thickness, cross sectional area (tunica intima+media) (CSA), and wall thickness/inner diameter ratio were studied in light microscopy.

Results: At the end of the experiment blood pressure increase accompanied by cardiac hypertrophy (increase of relative heart weight) was observed in both models of hypertensive animals. Morphometry of both arteries revealed in NO-deficient and SHR an increase of wall thickness, CSA, and wall thickness/inner diameter ratio. The inner diameter was increased only in thoracic aorta: in the carotid artery it was not changed. Administration of acetylcholine to the bath medium resulted in dose dependent relaxation of both arteries in normotensive animals. Dose dependent relaxation of both arteries was significantly blunted in NO-deficient rats. In contrast to this endothelium dependent relaxation to acetylcholine was not affected in both arteries in SHR. The arterial relaxation in SHR as well as residual relaxation in arteries of NO-deficient hypertension was completely inhibited after acute addition of L-NAME into the incubation medium.

Conclusions: The results of the study suggest that the increase of systolic blood pressure and accompanied changes in cardiovascular system are not primarily responsive for the decline of endothelium dependent relaxation in experimental hypertension.

Keywords: endothelium dependent relaxation; NO-deficient hypertension; spontaneous hypertension; morphometry; arterial wall

Published: March 1, 2015  Show citation