EXPRESSION OF AN INTER-ALPHA-TRYPSIN INHIBITOR HEAVY CHAIN-LIKE PROTEIN IN THE PIG ENDOMETRIUM DURING THE ESTROUS-CYCLE AND EARLY-PREGNANCY

In pigs, changes in an unidentified endometrial glycoprotein, pGP30, a re temporally associated with rapid trophoblast elongation and initial placental attachment on day 12 of gestation. Identification of endome trial pGP30 was undertaken through protein purification, NH2-terminal amino acid sequencing and cDNA sequencing of products generated throug h reverse transcription-polymerase chain reaction. Sequencing of 35 am ino acids from the NH2-terminal end of pGP30 revealed that the 30 kDa glycoprotein is a cleavage product from the C-terminal region of inter -alpha-trypsin inhibitor heavy chain 4 (I alpha IH4), previously known as inter-alpha-trypsin inhibitor heavy chain-like protein. IaIH4 is u nique compared with the three other inter-alpha-trypsin inhibitor heav y chains as it does not contain a binding site for bikunin that has se rine protease inhibitory activity and is sensitive to cleavage by kall ikrein. Endometrial gene expression of I alpha IH4 was detected during the oestrous cycle (days 0-18) and early pregnancy (days 10-18). Gene expression of I alpha IH4 appeared to be enhanced during the midlutea l phase (days 12 and 15) of the oestrous cycle and the period of troph oblast attachment (days 12-18). Expression of I alpha IH4 was not dete cted in day 12 conceptus tissue mRNA. Endometrial expression of I alph a IH4 in pigs may function as an acute phase protein for protection of the uterus from the inflammatory response induced by conceptus attach ment to the uterine epithelium.