Prostaglandin F 2α Prostaglandin E 2,Progesterone,20α-dihydroprogesterone and Ovarian 20α Hydroxysteroid Dehydrogenase Activity in Preparturient Pelvic Neurectomized Rats

Abstract

Summary

Several workers have reported that section of the pelvic parasympathetic nerves [pelvic neurectomy (PN)] in pregnant rats is compatible with pregnancy, but parturition is blocked. The cause of this blocked parturition remains unexplained. To determine if PN had a possible action on progesterone and prostaglandin, two endocrine mediators of labor, we neurectomized (PN) or sham-operated (S) rats on days 8-10 of pregnancy. Then on days 20, 21, 22, 23 and 24 (PN only) rats were lightly etherized and utero-ovarian vein (UOV) blood was collected, centrifuged and plasma frozen and stored at −60° until radioimmunoassay for progesterone, 20α-dihydroprogesterone (20α-ol), prostaglandin F_2α (PGF), and prostaglandin E₂ (PGE). One ovary from each rat was immersed in a BEEM capsule containing OCT compound, frozen and stored at −20° for 20α-hydroxysteroid dehydrogenase (20α-HSD) histochemistry.

Analysis of variance indicated a significant (P < 0.01) decline in plasma progesterone in the S animals on the days studied but the PN animals remained unchanged through day 22. Student's Newman-Keuls (SNK) analysis for multiple critical values indicated that plasma progesterone on days 20 and 21 was not different in the S animals but declined (P < 0.01) on day 22. Progesterone also declined on days 23 and 24 in PN animals. There was a significant increase (P < 0.05) between day 20, 21 and 22 plasma PGF in the S but no change in the plasma PGF in the PN animals on any of these days or on days 23 and 24. SNK analysis showed increased PGF (P < 0.05) on day 22 in the S animals. But UOV PGE did not change in the PN or S groups. The density and intensity of ovarian 20α-HSD reaction product was low in both S and PN rats on days 20 and 21. Increased density and intensity of ovarian 20α-HSD reaction product was characteristic of five animals on day 22 and PN rats on days 22, 23 and 24. Collectively, these results indicate that the pelvic nerves participate in the orchestration of endocrine and uterine events in the pre-parturient and parturient periods in the rat.