Expression of estrogen and androgen receptor in the bovine gastrointestinal tract

Reproductive and maturational nutritive needs are examples for situations in which alterations in circulating concentrations of sex steroids are associated with changes in gastrointestinal function. In order to investigate whether there is a causal relationship between sex steroids and gastrointestinal function, we aimed to investigate the responsiveness for androgens and for estrogens of the bovine gastrointestinal tract. Using Northern blot analysis, estrogen receptor (ER) mRNA was detected in rumen tissue. Comparing the ER expression in rumen from females of different reproductive stages, we found that no differences related to cycle stage, pregnancy or parturition could be detected. In contrast, the ER expression rates in the uterus of the respective animals showed the same dependency of reproductive stage as demonstrated earlier for the ER protein, indicating that there might be a tissue specific regulation of ER. By in-situ hybridization of rumen tissue sections the expression of ER was localized in the epithelium of the papillae. In the muscular layer no positive signals for ER mRNA were observed. Above rumen, the presence of ER and androgen receptor (AR) mRNA was determined in various intestinal tissues using reverse transcription (RT) and polymerase chain reaction (PCR). Primers were selected from the bovine androgen and estrogen receptor sequence to amplify parts of the sequence coding for the hormone binding part of the respective receptor. The PCR amplifies were subsequently electrophoresed on 1% agarose gels and visualized by ethidium bromide staining. ER mRNA expression was demonstrated in reticulum, omasum, abomasum, duodenum, jejunum, ileum, caecum and colon. AR mRNA expression was not determined in the forestomaches, but was present in all intestinal segments investigated.(ABSTRACT TRUNCATED AT 250 WORDS)