Testicular function, and associated testosterone concentration, declines with advancing age and an impaired O2 supply may contribute to this reduction. We hypothesized that there would be a reduced microvascular PO2 (PO2m) in the testes from aged rats, and this reduced PO2m would be associated with impaired vasomotor control in isolated resistance arterioles. Given the positive effect of exercise on PO2m and arteriolar function, we further hypothesized that there would be an enhanced PO2m in the testes from aged animals after aerobic exercise training. Testicular PO2m was measured in vivo via phosphorescence quenching in young and aged sedentary (SED) and exercise trained (ET; 15 m/min treadmill walking, 15 degree incline, 5 days/week for 10 weeks) male Fischer-344 rats. Vasoconstriction to alpha-adrenergic (norepinephrine (NE) and phenylephrine (PE)) and myogenic stimuli in testicular arterioles was assessed in vitro. In the sedentary animals, testicular PO2m was reduced by ~50% with old age (aged SED 11.8 ± 1.9 vs. young SED 22.1 ± 1.1 mmHg). Contrary to our hypothesis, exercise training did not alter PO2m in the aged group and reduced testicular PO2m in the young animals, abolishing age-related differences (young ET 10.0 ± 0.8 vs. aged ET 10.7 ± 0.9 mmHg). Vasoconstrictor responsiveness to NE and PE was diminished in aged compared to young (NE, young SED 58 ± 2 vs. aged SED 47 ± 2%; PE, young SED 51 ± 3 vs. aged SED 36 ± 5%). Exercise training did not alter maximal vasoconstriction to NE in young or aged groups. In summary, advancing age is associated with a reduced PO2m and impaired adrenergic vasoconstriction. The diminished testicular microvascular driving pressure of O2, and associated vascular dysfunction, provides mechanistic insight into the old age-related decrease in testicular function and a reduced PO2m may contribute, in part, to reduced fertility markers after exercise training.
- microvascular PO2
- Copyright © 2011, American Journal of Physiology - Regulatory, Integrative and Comparative Physiology