Agonist-induced vasomotor responses and eNOS expression are similar in small mesenteric arteries of UM-HET3 and C57BL/6J mice

Objective: While inbred C57BL/6J (C57) mice are commonly used in resistance artery function studies, genetically diverse UM-HET3 (HET3) mice have emerged as a more robust model of large artery dysfunction. HET3 resistance artery function, however, remains unexamined. The purpose of this study is to examine the dose-responses to the vasoconstrictor phenylephrine (PE) and the endothelium-dependent vasodilator acetylcholine (ACh) in mesenteric resistance arteries of HET3 mice compared C57 mice of both sexes. Additionally, the expression of eNOS protein, an enzyme contributing to ACh-induced vasodilation, was compared in these arteries between the strains and sexes. Hypothesis: Vasomotor responses to PE and ACh, and eNOS protein expression, will be similar between HET3 and C57 small mesenteric arteries of both sexes. Methods: Male (M) and female (F) mice (8-14 wk old) of C57 and HET3 mice were used. Mesenteric arteries of the 1 st and 2 nd order were isolated and cannulated for pressure myography. At physiological pressure (75 mmHg), arteries were held at 37° C with MOPS-buffered physiological salt solution (PSS) superfusion, and PSS + 1% BSA luminal perfusion, with no luminal flow. After 30 min of equilibration to assess basal tone, cumulative addition of PE [10 -9 -10 -5 M] to the superfusate and measurement of luminal diameter 3 min after each dose was performed (in a strain and sex-blinded manner). This was followed by cumulative dose-response measurements to ACh [10 -10 -10 -4 M], then 10 min of flushing with Ca ++ -free PSS to determine the maximal diameter. eNOS protein expression was measured by western blot and normalized to gapdh and protein expression on the same blot. Results: PE-induced peak vasoconstriction responses (range: 71.0-73.8% constriction) and PE sensitivities [EC-50’s (mean ± SEM): HET3-M: 1.32 ± 0.35 µM (n=11), HET3-F: 1.50 ± 0.37 µM (n=12), C57-M: 1.54 ± 0.34 µM (n=12), C57-F: 1.03 ± 0.28 µM (n=11)] were similar between groups. ACh-induced peak vasodilation responses (range: 63.1-73.4%) were also similar between groups. However, ACh EC-50 was lower (i.e. more sensitive) in HET3-F (0.047 ± 0.021 µM) compared to C57-F (4.23 ± 1.97 µM) (p<0.05). ACh EC-50 for HET3-M (0.80 ± 0.77 µM) and C57-M (0.33 ± 0.16 µM) were not different from the other groups. eNOS/gapdh protein expression and eNOS/total protein expression were similar between the groups. All group comparisons were by 1-way ANOVA with Bonferroni post-hoc test. Conclusion: This study reveals that HET3 mesenteric resistance arteries exhibit similar vasomotor responses to C57 arteries, with greater ACh sensitivity in HET3 females. HET3 mice are therefore a valid model for resistance artery research. Funded by NIH-1R15HL150570-01A1 (R.L-W.), the William & Mary Charles Center Undergraduate Summer Research Grant (E.W., K.S.), and the William & Mary FUSE program (C.H.). This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.