PARENT SESSION

(T578) EXPRESSION OF INDUCIBLE NITRIC OXIDE SYNTHASE IN REPEATED BIOPSIES OF THE BOVINE CERVIX DURING LATE GESTATION AND PARTURITION.

Breeveld-Dwarkasing, Vidya¹, Aalberts, Marian¹, Van Dissel-Emiliani, Federica¹, Van Tol, Helena¹, Taverne, Marcel¹, ¹ Utrecht University, Utrecht, The Netherlands

ABSTRACT- Nitric oxide (NO) plays a key role in the processes leading to cervical softening prior to labor. Inducible nitric oxide synthase (iNOS) contributes most to the increased production of NO during labor, as demonstrated in the rat cervix, or at term, as shown in women. Changes in expression of iNOS during late gestation have not yet been studied longitudinally in women, because repeated biopsing could not be performed. Here, we report on iNOS mRNA (n=6) and protein expression (n=4) in serial cervical biopsies of pregnant pluriparous cows taken around day 225, 250 and 275 of pregnancy and within 1 hour after calving (biopsy 1, 2, 3 and 4, resp.), using quantitative RT-PCR and Western blotting. iNOS mRNA expression decreased from the 1^st biopsy onwards, differences being significant between the 2^nd and 3^rd (P<0.05) and between the 3^rd and 4^th biopsy (P<0.05). This is in contrast with findings in the rat, but shows similarities with human studies in which iNOS levels also did not increase between late gestation and labor. iNOS protein expression was present during late pregnancy (biopsies 1-3) but was almost undetectable after calving. Immunohistochemical analysis of biopsies showed positive staining in endothelium and epithelium. In early biopsies, iNOS expressing stromal cells were predominantly spindle shaped (fibroblasts and smooth muscle cells). Overall, iNOS expression decreased at calving and mostly mononuclear inflammatory cells were positively stained. These results suggest that iNOS from spindle shaped cells contributes to prepartum cervical ripening. Although iNOS in the inflammatory cells apparently does not highly contribute to the total expression levels in the tissue during calving, it may be important for local tissue repair mechanisms during postpartum cervical involution.

KEY WORDS: cervical ripening, cervix, iNOS, nitric oxide