Effect of ovarian steroids on nitric oxide synthase in the rat uterus, cervix and vagina

The effects of estrogen (E-2), progesterone (P) and E-2 and P (E-2 + P) wer e examined on nitric oxide synthase (NOS) activity in both cytosolic and pa rticulate fractions isolated from the rat uterus, vagina, cervix and cerebr al cortex. Additionally plasma nitrate + nitrite (NO3 + NO2) levels were me asured in control and hormone treated rats. Cytosolic NOS was the predomina nt form being approximately 80% of the total in all four tissues. NOS activ ity in both fractions from all tissues was highly Ca-dependent (> 90%). Amo ng the reproductive tract tissues, the highest activity was found in the ce rvix, which was nearly 5- and 2-fold higher than the uterus and vagina, res pectively. NOS activity in the cerebral cortex was by far the highest being 5-fold higher than in the cervix. In contrast to the cortex, E-2 treatment downregulated cytosolic NOS in all reproductive tract tissue, but this was statistically significant in only uterus. When compared with E-2 treated r ats, P increased cytosolic NOS in uterus, vagina, and particulate NOS in th e cervix. The data do not give any indication whatsoever of differential ef fects of P in the uterus and cervix. (C) 2001 Elsevier Science Inc. All rig hts reserved.