Chronic Prenatal Hypoxia Down-Regulated BK Channel Β1 Subunits in Mesenteric Artery Smooth Muscle Cells of the Offspring

Abstract

Background/Aims: Chronic hypoxia in utero could impair vascular functions in the offspring, underlying mechanisms are unclear. This study investigated functional alteration in large-conductance Ca²⁺-activated K⁺ (BK) channels in offspring mesenteric arteries following prenatal hypoxia. Methods: Pregnant rats were exposed to normoxic control (21% O₂, Con) or hypoxic (10.5% O₂, Hy) conditions from gestational day 5 to 21, their 7-month-old adult male offspring were tested for blood pressure, vascular BK channel functions and expression using patch clamp and wire myograh technique, western blotting, and qRT-PCR. Results: Prenatal hypoxia increased pressor responses and vasoconstrictions to phenylephrine in the offspring. Whole-cell currents density of BK channels and amplitude of spontaneous transient outward currents (STOCs), not the frequency, were significantly reduced in Hy vascular myocytes. The sensitivity of BK channels to voltage, Ca²⁺, and tamoxifen were reduced in Hy myocytes, whereas the number of channels per patch and the single-channel conductance were unchanged. Prenatal hypoxia impaired NS1102- and tamoxifen-mediated relaxation in mesenteric arteries precontracted with phenylephrine in the presence of N^ω-nitro-L-arginine methyl ester. The mRNA and protein expression of BK channel β1, not the α-subunit, was decreased in Hy mesenteric arteries. Conclusions: Impaired BK channel β1-subunits in vascular smooth muscle cells contributed to vascular dysfunction in the offspring exposed to prenatal hypoxia.