POTENTIAL ROLES FOR GONADAL-STEROIDS AND INSULIN-LIKE-GROWTH-FACTOR-IDURING FINAL CERVICAL RIPENING

Objective: To determine whether gonadal steroids and insulin-like grow th factor I influence the final cervical remodeling during parturition . Methods: Cervical biopsies were obtained transvaginally before labor (n = 10) and after spontaneous cervical ripening and vaginal delivery (n = 20). Levels of estrogen and progesterone receptors, their messen ger RNAs, insulin-like growth factor I messenger RNA, and serum estrad iol and progesterone were measured. Collagen and proteoglycan , concen trations and compositions were measured to estimate the degree of cerv ical ripeness. Results: The concentrations of estrogen and progesteron e receptors decreased in comparison with the clinically unripe cervix before labor. The median estrogen receptor concentration (range) decre ased from 10 (2-18) to 4.5 (2-14) fmol/mg protein (P < .01), and the p rogesterone receptor concentration from 105.5 (32-153) to 74 (30-115) fmol/mg protein (P < .05), whereas their messenger RNA levels were unc hanged. The insulin-like growth factor I messenger RNA concentration d eclined from 16.1 (8.4-20.4) at term to 8.9 (1.5-18.5) amol/mu g DNA a fter parturition (P < .01). The collagen solubility by pepsin increase d, but not significantly, and the collagen concentration was unchanged . The concentration of small proteoglycans, mainly decorin, decreased from 1.59 (1.20-1.97) to 0.84 (0.24-1.41) mu g/mg wet weight (P < .001 ), and the concentration of versican increased, but not significantly (P = .07). Conclusion: Concentrations of estrogen and progesterone rec eptors and insulin-like growth factor I messenger RNA were decreased s ignificantly after spontaneous cervical ripening in comparison to leve ls before labor. These changes coincided with a tendency toward increa sed collagen solubility and a decline in concentration of small proteo glycans, which probably alters collagen organization, thus allowing fo r cervical softening and dilation. These observations suggest that gon adal steroids influence the final cervical remodeling during parturiti on, an influence perhaps mediated by insulin-like growth factor I. (C) 1997 by The American College of Obstetricians and Gynecologists.