Impaired endothelium-derived hyperpolarization-type relaxation in superior mesenteric arteries isolated from female Otsuka Long-Evans Tokushima Fatty rats.

Endothelium-derived hyperpolarization (EDH) is an important signaling mechanism of endothelium-dependent vasorelaxation, and little attention has been paid to the EDH-type responses in female metabolic syndrome such as that observed with type-2 diabetes. We previously reported that EDH-type relaxation was impaired in superior mesenteric arteries from male Otsuka Long-Evans Tokushima Fatty (OLETF) rat, a model of type-2 diabetes, however, the response was unclear in female OLETF rat. Thus, the aim of this study was to examine if EDH-type relaxation was altered in superior mesenteric arteries isolated from female OLETF rats compared to age-matched, control female Long-Evans Tokushima Otsuka (LETO) rats at age 50-59 weeks. We investigated concentration-relaxation curves for acetylcholine (at age 50-53 weeks), NS309 (an activator of small- and intermediate-conductance calcium-activated potassium channels) (at age 50-53 weeks), and GSK1016790A (an agonist of transient receptor potential vanilloid type 4, TRPV4) (at age 58 or 59 weeks) in the presence of the nitric oxide synthase inhibitor N-nitro-L-arginine and the cyclooxygenase inhibitor indomethacin to investigate EDH-type responses in the superior mesenteric artery. Obesity, mild hyperglycemia, hyperinsulinemia, and hyperlipidemia (i.e., increased total cholesterol, triglyceride, and non-esterified fatty acids) were more frequent in OLETF rats than in age-matched LETO rats at age 50-53 weeks. Acetylcholine-, NS309-, and GSK1016790A-induced relaxations in arteries from OLETF rats were all significantly reduced compared to those in LETO rats. These results indicated that EDH-type relaxations were impaired in female OLETF rats. This novel experimental model may provide new insights into vascular dysfunction in metabolic syndrome in females.