COX-1 and -2 gene expression can be regulated at both the transcriptional and the posttranscriptional levels, and species differences may exist at both levels. Transcription induced in murine or chicken embryo fibroblasts by mitogens or by oncogene-induced transformation occurs rapidly, and maximal levels are seen at 15-30 min, followed shortly by COX-2 mRNA and protein accumulation, indicating transcriptional regulation in these instances. In a human cell line and in cultured human endometrial and granulosa cells, interleukin-1p or hCG induces rapid and transient COX-2 gene transcription as well as prolongation of the half-life of the mRNA. In sheep injected with 10 IU of OT, COX-2 mRNA expression can be demonstrated after a delay of 7-8 min; it reaches maximal levels in 25 min, and declines to baseline by 60-90 min after the injection. In the present experiments COX-2 mRNA was still detectable 2 h after the injection—probably because a larger dose of OT was administered, since the ligand-induced COX-2 transcription has been shown to be dose dependent. ventolin 100 mcg
The finding of relatively low concentrations of COX-2 mRNA in endometrium and myometrium of cows at term and during labor was unexpected in view of the present findings and considering that significant amounts of OT are released from the posterior pituitary during parturition. The reason for the observed low COX-2 transcript levels may be the long time, 2-3 h, that elapsed between observation of a cow in labor out in the fields (followed by transportation to the Meats Laboratory) and the removal of the tissues.