Estrogen-regulated Expression of SK3 Channel in Rat Colonic Smooth Muscle Contraction

Aims: Estrogen can induce inhibition of colonic smooth muscle contraction in male and female mice, which may lead to constipation; however, the mechanisms of inhibition are poorly understood. Hence, this study investigated the effect of estrogen on rat colonic smooth muscle contraction and role of small-conductance Ca-activated K 3 (SK3) and transcription factors (Sp1 and Sp3) in the underlying mechanisms.

Main Methods: The experiment included 24 female Sprague-Dawley (SD) rats divided into 4 groups. The rats were oophorectomized surgically, and a silicone tube containing blank solvent, 0.3 mg/mL estrogen (E2), equal-concentration of estrogen and estrogen receptor antagonist (EI), and bovine serum albumin-E2 (BSA-E2) was implanted. The rats were sacrificed on day 14. The molecular insights were confirmed using real-time quantitative reverse transcription PCR (qRT-PCR) and western blot analyses to determine the effect of estrogenic stimulation on gene and protein expression analyses, respectively.

Key Findings: The E2 group showed significantly greater SK3 expression (P < .005) compared with other groups and significantly lowers smooth muscle cell (SMC) contractility (P < .005). Estrogen stimulation and SK3 overexpression resulted in a significant decrease (P < .05) in Ca mobilization in the E2 group versus the control group. Further, the E2 group showed significantly higher Sp1 mRNA (P < .05) but lower Sp3 mRNA expression (P < .05) and protein expression (P < .001) compared with other groups.

Significance: E2 may promote SK3 expression by its genomic effect and inhibit colonic contraction by affecting SK3 expression via an interaction between Sp1 and Sp3.