Expression of Insulin-Like Growth Factor 1 (IGF-1) and Epidermal Growth Factor (EGF) Receptors and the Effect of IGF-1 and EGF on Androgen and Estrogen Release in the Myometrium of Pigs—In Vitro Study

SIMPLE SUMMARY: The uterus of pregnant and nonpregnant females produces steroid hormones. The activity of uterine steroidogenesis is altered by the female physiological status, but its regulation is not well understood. This study tested whether growth factors may regulate steroid hormone production in the myometrium. To do so, myometrial slices were isolated from pigs during days 10 or 11, 12 or 13 and 15 or 16 of the estrous cycle and early pregnancy and it was determined whether the tissue possesses potential to respond insulin growth factor 1 (IGF-1) or epidermal growth factor (EGF) and whether they affect androstenedione (A(4)), testosterone (T), estrone (E(1)) and estradiol-17β (E(2)) production in the myometrium. The results showed that myometrial receptivity to IGF-1 and EGF was altered in pregnant and nonpregnant pigs and IGF-1 and EGF affect steroid hormone release in the myometrium. The observed alterations were limited to specific days of the estrous cycle and pregnancy. In conclusion, IGF-1 and EGF may be considered as specific regulators of myometrial steroid hormone production. ABSTRACT: Porcine myometrium possesses steroidogenic activity but its regulation is not well understood. It was hypothesized that the regulators of myometrial steroidogenesis are insulin-like growth factor 1 (IGF-1) and epidermal growth factor (EGF), which were found to modulate the steroidogenic activity of the endometrium and embryos. Myometrial slices were collected from gravid and nongravid pigs on days 10 or 11, 12 or 13 and 15 or 16 and studied for: (1) the relative abundance of IGF-1R and EGFR mRNA transcripts and proteins, to determine myometrial readiness to response growth factors treatment and (2) the effect of IGF-1 or EGF on the myometrial release of androstenedione (A(4)), testosterone (T), estrone (E(1)) and estradiol-17β (E(2)). The results showed that the relative expression and abundance of IGF-1R and EGFR in the myometrium were altered regarding the female reproductive status. During the estrous cycle, EGF increased myometrial release of A(4) on days 12–13 and E(2) on days 15–16. In gravid pigs (days 15–16), IGF-1 and EGF increased the E(1) release. In conclusion: (1) porcine myometrium possesses the potential to respond to IGF-1 and EGF treatment, (2) EGF significantly increases myometrial A(4) and E(2) release in cyclic pigs, while IGF-1 and EGF increase the E(1) release in gravid pigs.