The proportion of both COX-1 and COX-2 mRNA was consequently greater in total RNA from the purified COX-expressing cells than from intact endometrial tissue, and COX-1 mRNA was therefore measurable in RNA from the purified cells. An alternative explanation is that, similarly to expression of OTR gene in bovine endometrial epithelial cells, transcripts of the constitutively expressed COX-1 gene increased spontaneously under the in vitro conditions. proventil inhaler
Considerable species variation in COX-1 and -2 gene expression in uterine tissues exists. Unlike pregnant cows, pregnant sheep have been found to express COX-1 gene transcripts in relatively high concentrations in endometrium, myometrium, cotyledons, and amnion.
Nevertheless, only COX-2 mRNA concentrations in endometrium and myometrium increased during labor, suggesting that COX-2 is more important than COX-1 for prostanoid production during labor also in sheep. As in cows, COX-2 mRNA expression in ewes was most pronounced in cotyledons, with no difference between tissue from ewes in labor and not in labor. COX-2 seems to be the dominant isoform expressed during parturition in human uterine tissues. Guinea pig endometrium resembles bovine endometrium in expressing mainly COX-2 mRNA and protein; COX-1 mRNA expression is very weak and is not affected by ovarian hormones. In rats, on the other hand, uterine expression of COX-1 isoform of the enzyme equals that of the COX-2 isoform, and the two isoforms increase in parallel during pregnancy. In isolated myometrium of pregnant rats, only the COX-1 isoform of the enzyme has been found. Species variations apparently exist also in the male reproductive tissues. Seminal vesicular gland of rams contains prostaglandins in great abundance and is a rich source of COX-1 isoenzyme, whereas seminal fluid of bulls contains little if any prostaglandins. Our findings of relatively low expression of COX-1 mRNA in the seminal vesicular gland and prostate of bulls are in agreement with this report.