Comparisons of vascular reactivity of isolated aortas from high‐ and low‐capacity running rats

The selection for high‐ or low‐capacity (HCR/LCR) running in rats revealed a divergence in expression of cardiovascular diseases risk factors. We tested the hypotheses that LCR rats have a poorer vascular responses relative to HCRs, and that the selection preserved gender differences. Cumulative dose‐response curves were generated in thoracic aortic rings to K + , phenylephrine (PE), norepinephrine (NE), serotonin (5‐HT), sodium nitroprusside (SNP), acetylcholine (ACH), and forskolin (FSK) from HCR‐female (Hf), HCR‐male (Hm), LCR‐female (Lf) and LCR‐male (Lm) rats. The magnitude of contractive responses by K + , PE and 5‐HT were significantly higher in female than in male rats of both strains. The SNP, ACH and FSK relaxations were significant greater in females than in males as was the Hm vs Lm relaxation. SNP EC 50 values were 0.010 ± 0.004, 0.023 ± 0.008, 0.013 ± 0.006, 0.081 ± 0.034 μM; ACH EC 50 were 0.038 ± 0.006, 0.014 ± 0.002, 0.032 ± 0.016, 0.110 ± 0.056 μM; and for FSK the EC 50 were 2.64 ± 0.96, 7.06 ± 2.13, 3.21 ± 1.16, 11.64 ± 2.80 μM, in Hf, Hm, Lf and Lm, respectively. Our results demonstrated a significant gender differences in magnitude of contractile and relaxant responses, and a strain difference in dose sensitivity of relaxant reactivity between HCR and LCR male but not between female rats, which might involve an imbalance in NO‐cyclic nucleotide signaling.