Effects of Testosterone Deficiency and Angiotensin II-Induced Hypertension on the Biomechanics of Intramural Coronary Arteries

Abstract

Background: Andropause and hypertension also increase the risk of coronary artery damage.

Aim: To investigate the effect of testosterone deficiency and hypertension on intramural coronary vessels.

Methods: 4 groups of 8-week-old Sprague-Dawley rats were studied: control male (Co, n=10), orchidectomized male (OCT, n=13), angiotensin (AII) hypertensive male (AII, n=10), and AII hypertensive and OCT (AII + OCT, n=8). Surgical orchidectomy was performed, and an osmotic minipump was inserted for chronic angiotensin II infusion (100 ng/min/kg). After 4 weeks, spontaneous tone and biomechanical properties of the intramural coronary resistance artery were investigated in vitro, by pressure microarteriography.

Outcomes: Morphology and biomechanics of the intramural coronaries were evaluated: the outer diameter, wall thickness-to-lumen diameter ratio, and tangential wall stress in the contracted and relaxed states.

Results: The outer diameter was reduced in OCT and AII + OCT groups (on 50 mmHg 315 ± 20 Co; 237 ± 21 OCT; 291 ± 16 AII, and 166 ± 12 μm AII + OCT). The increased wall thickness-to-lumen diameter ratio resulted in lower tangential wall stress in AII + OCT rats (on 50 mmHg 19 ± 2 Co; 24 ± OCT; 26 ± 5 AII, and 9 ± 1 kPa AII + OCT). Spontaneous tone was increased in the hypertensive rats (AII and AII + OCT groups) (on 50 mmHg 7.7 ± 1.8 Co; 6.1 ± 1.4 OCT; 14.5 ± 3.0 AII, and 17.4 ± 4.1 % AII + OCT).

Clinical implications: Andropause alone can be considered as a cardiovascular risk factor that will further exacerbate vascular damage in hypertension.

Strengths & limitations: A limitation of our study is that it was performed on relatively young rats, and the conclusions might not apply to coronary remodelling in older animals with slower adaptation processes.

Conclusions: Testosterone deficiency and hypertension damage the mechanical adaptation of the vessel wall additively: double noxa caused inward eutrophic remodeling and increased tone. Jósvai A, Török M, Mátrai M, et al. Effects of Testosterone Deficiency and Angiotensin II-Induced Hypertension on the Biomechanics of Intramural Coronary Arteries. J Sex Med 2020;17:2322-2330.

Keywords: Biomechanics; Castration; Hypertension; Rat Andropause Model; Resistance Coronary Artery; Testosterone.