Chronic swimming training resulted in more relaxed coronary arterioles in male and enhanced vasoconstrictor ability in female rats.

Background: Exercise training is associated with hypertrophy of left ventricle (LV). The aim of the present study is to evaluate sex differences in the adaptation of the coronary contractile function in physiological left ventricular hypertrophy induced by long-term swim training.

Methods: Thirty-two Wistar rats were randomly divided into 4 groups: exercised male (ExM), exercised female (ExF), untrained control male (CoM), and untrained control female (CoF). The trained animals underwent a 12-week-long swim training program. After finishing the training program, LV morphology and function were checked by echocardiography. The spontaneous tone, thromboxane (TxA2) agonist-induced vascular contractility and non-endothelial dilatation of the isolated intramural coronary resistance artery were examined by pressure microangiometry. The thromboxane receptor (TxA2R) protein expression in the wall of coronary arteries was examined using immunohistochemistry.

Results: The LV mass index was significantly higher in the ExM and ExF groups, furthermore the LV mass index was significantly higher in female than in male animals. ExM animals had lower spontaneous tone than ExF. TxA2 agonist-induced tone was raised only in ExF animals. The resistance coronary artery of exercised male animals had a significantly lower level of TxA2R positivity compared to exercised females.

Conclusions: Both sexes broaden their range of contractility following chronic swimming, but the vessel tone shifted toward contraction in exercised female rats, while these values shifted toward relaxation in males. These observations underline the significance of identifying potential gender differences in the chronic exercise-induced coronary vascular remodeling in human athletes.