Differential expression of cyclooxygenase-2 around the time of elongation in the pig conceptus

Alterations in uterine luminal fluid composition as a result of conceptus estradiol-17β production are believed to play a significant role in the loss of 30–40% of potential pig conceptuses. Shortly after the initiation of conceptus estradiol-17β synthesis and secretion, the conceptuses are transformed from 1 cm spheres to 2–5 cm tubular forms and finally to filamentous threads of variable length via a process known as elongation. We have attempted to characterize gene products whose expression is either initiated or terminated as the conceptus elongates. Using RNA fingerprinting, we determined that the inducible form of the rate-limiting enzyme in prostaglandin synthesis, cyclooxygenase-2, is expressed in the filamentous pig conceptus, but not in either the spherical or transitional morphologies. Furthermore, increased expression of cyclooxygenase-2 by the filamentous conceptus was associated with increases in the content of prostaglandins (particularly prostaglandin E2) found in uterine luminal fluid.