Testosterone relaxes rabbit coronary arteries and aorta

Area of Science:

• Cardiovascular Physiology
• Endocrinology
• Pharmacology

Background:

• Premenopausal women exhibit protection against coronary heart disease (CHD), potentially due to estrogen's cardiovascular benefits.
• Testosterone's direct cardiovascular effects remain largely unexplored, despite potential implications for sex-based differences in CHD incidence.
• This study investigates the direct impact of testosterone on vascular tissues.

Purpose of the Study:

• To assess the direct in vitro effect of testosterone on rabbit coronary arteries and aorta.
• To evaluate the relaxation responses to various testosterone analogues.

Main Methods:

• Isometric tension measurements were performed on isolated rabbit coronary artery and aortic rings.
• Responses to testosterone were assessed in rings pre-contracted with prostaglandin F2 alpha or KCl.
• The roles of endothelium, nitric oxide synthase, prostaglandin synthetase, guanylate cyclase, potassium channels, aromatase, and testosterone receptors were investigated.

Main Results:

• Testosterone induced significant relaxation in both rabbit coronary arteries and aorta, independent of the presence of endothelium.
• The relaxing effect of testosterone was more pronounced in coronary arteries than in the aorta.
• Testosterone demonstrated greater potency as a relaxing agent compared to its analogues tested.

Conclusions:

• Testosterone mediates endothelium-independent relaxation in rabbit coronary arteries and aorta via mechanisms involving potassium conductance, not cyclic GMP or prostaglandin I2.
• The relaxation effect is independent of sex and classic testosterone receptors.
• Testosterone is a potent vasodilator of rabbit coronary arteries, exceeding the effects of its analogues.