SYNTHESIS OF ALPHA-1-ANTICHYMOTRYPSIN AND ALPHA-1-ANTITRYPSIN BY HUMAN TROPHOBLAST

Alpha1-antichymotrypsin (alpha1-ACHY) and alpha1-antitrypsin (alpha1-A T) are closely related glycoprotein protease inhibitors, present in pl asma and other extracellular fluids, that neutralize proteases release d by leukocytes in response to trauma and inflammatory stimuli. Both i nhibitors are synthesized primarily by hepatocytes, although lower lev els of synthesis by monocytes and breast and intestinal epithelial cel ls have been demonstrated. Recently, the immunohistochemical localizat ion of alpha1-AT and alpha1-ACHY in intrauterine and extrauterine huma n trophoblastic tissue has been reported. In the present study, we hav e sought to determine whether human trophoblast is also able to synthe size alpha1-AT and alpha1-ACHY. Messenger RNA for both inhibitors was found by Northern blotting in chorionic villi obtained from first trim ester and term placenta. Substantial differences in messenger levels f or both inhibitors among individual placentas were noted. Alpha1-ACHY and alpha1-AT messenger was also present in trophoblast cells in prima ry culture. Synthesis of alpha1-AT and alpha1-ACHY protein was demonst rated by SDS-PAGE after immunoprecipitation of [S-35]-labeled alpha1-A T and alpha1-ACHY from conditioned media of trophoblast cells in cultu re metabolically labeled with [S-35]-methionine. It is of some interes t that the M(r) of the alpha1-AT and alpha1-ACHY secreted by trophobla st were 50 000 and 49 000, respectively, compared with 54 000 and 68 0 00 for these proteins in plasma (or secreted by HepG2 human hepatoma a nd MCF-7 human breast cancer cells). After enzymatic deglycosylation, the M(r) of the alpha1-AT and alpha1-ACHY secreted by trophoblast and HepG2 cells were all approximately 46 000, suggesting incomplete glyco sylation of the inhibitors released by trophoblast.