Untersuchen zur Regulation der uterinen und ovariellen Durchblutung sowie der Expression von Stickstoffmonoxidsynthasen und Östrogenrezeptoren im Verlauf des Zyklus und der Frühgravidität bei der Stute

The aim of the present study was to estimate the influence of uterine NOS-system and the sexual steroids estrogen and progesterone on the blood supply of the uterus and the ovaries. Five trotter mares were examined in total during four estrous cycles and one early pregnancy. The investigations contained color Doppler- and ultrasound recordings as soon as the extraction of blood samples and endometrial biopsies. The first cycle was medically uninfluenced and investigations were carried out on Days 0 (= ovulation), 1, 5, 11, 15 and daily during estrous, whereas in estrous only one endometrial biopsy was taken. In the second cycle luteal regression was induced on Day 5 of diestrous with the PGF2α-analogon Tiaprost (Ilirenâ, 450 mg i.m.) and in estrous ovulation was induced with hCG (Choriolutinâ, 2500 IE i.v.), when the size of one follicle reached 35 mm. Investigations were carried out in this cycle immediately before giving PGF2α and 0.5, 1, 3, 6, 12, 24, 36, 48 hours after that and then once a day up to ovulation. Endometrial biopsies were taken in each case before induction of luteolysis, 12 and 36 hours after that, before injection of hCG and immediately after ovulation. During the further two cycles the mares were treated orally with the NO donor ISDN (ISDN 40â, 30 mg, twice a day). Investigations were carried out on Days 0, 1 and 5 of the first cycle (ISDN I), as well as on Days 11, 15 and during estrous of the second cycle (ISDN II). During early pregnancy color Doppler recordings and blood samples were taken on Days 0, 1, 5, 11 and 15 of pregnancy, while endometrial biopsies were only gained on day 15. The analysis of uterine blood flow was based on the time-averaged maximum velocity (TAMV). Estrogens and progesterone were measured by an enzyme immunoassay. Nitrate concentrations were evaluated using Griess reacting. Total RNA was isolated from endo-metrial biopsies. Transcriptes encoding the estrogen receptors a and b and the endothelial as well as the inducible nitric oxide-synthase (eNOS and iNOS) were quantified by RT-PCR-analysis. The expression of eNOS-mRNA in control, as well as in the PGF2a-induced cycle, followed a consistent wavelike pattern (p < 0.05 and p < 0.0001). Both, eNOS and iNOS, showed their maximum of expression especially on Day 5 of diestrous and during estrous, when the highest levels of either progesterone or estrogen were measured. In the PGF2a-induced cycle, a significant connection between eNOS and progesterone was proved (p < 0.05). There was a positive correlation between the expression of the eNOS-mRNA and the uterine blood flow (p < 0.05) in the control cycle. In the PGF2a-induced cycle these two parameters also showed a similar cyclic pattern. The levels of estrogen-receptors in the endometrium or concentrations of estrogen in plasma were not related to the endometrial NO-synthases or to TAMV values. Plasma concentrations of nitrate were independent from the stage of estrous cycle and consequently were proved as unsuitable for the question raised here (in this case). The application of the NO donor ISDN leaded to a marked decrease of the uterine NOS-expression when compared with control cycle (p < 0.0001). An increase of uterine or ovarian perfusion during the application of ISDN was not provable (p > 0.05). In result of the biopsies on day 5 and of simultaneous ISDN application luteolysis was induced next to all mares. On day 15 of pregnancy, an increase in uterine and ovarian perfusion as well as an enhancement in iNOS-mRNA expression was observed. In conclusion, the results of this study indicate that the endometrial NO-synthases play an important role in the regulation of uterine blood supply during estrous cycle and pregnancy of the mare. Progesterone as well as estrogen seem to stimulate the endometrial expression of eNOS and iNOS, by which these hormones may indirectly influence uterine and ovarian blood flow.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Ludwig-Maximilians-Universität

Year

2003

Author dc:creator

• Rohr, Simone

Repository record source_url

https://edoc.ub.uni-muenchen.de/1193/

OAI identifier oai:identifier

oai:edoc.ub.uni-muenchen.de:1193