Synthesis of acute-phase alpha 2-macroglobulin during inflammation and pregnancy.

A recent investigation of acute-phase alpha 2-macroglobulin (AP alpha 2M) concentration in the rat during pregnancy demonstrated a bimodal distribution, for which we suggested a maternal source of AP alpha 2M in early gestation and a fetal source in late gestation. This interpretation was supported by the findings of the present study, which employed organ culture techniques, incorporation of [35S]methionine, immunoprecipitation of radioactivity, and fluorography to measure synthesis of AP alpha 2M in specific fetal, adult, and maternal tissues. Preliminary results indicated that in adult male rats treated with croton oil (compared with nontreated males), AP alpha 2M was synthesized in kidney, spleen, thymus, and lymphocytes by 48 hr post induction, but synthesis in the liver was not evident. In the pregnant rat from 12 to 16 days (compared with nonpregnant females), synthesis of AP alpha 2M was high in metrial gland, moderate in spleen, thymus and lymphocytes, and absent in liver; at 21 days, synthesis of AP alpha 2M in these four maternal tissues had declined. Fetal synthesis of AP alpha 2M in yolk sac (12 to 16 days) and in liver (15 to 16 days) was significantly elevated, and at 21 days fetal liver still displayed marked synthesis. These data are consistent with the interpretation that an early maternal source of AP alpha 2M synthesis is the metrial gland and that in the fetus both yolk sac and liver are major sources of AP alpha 2M, the latter tissue continuing synthesis into late gestation. Lymphopoietic and lymph-containing tissues appear to be major sites of AP alpha 2M synthesis during inflammation and pregnancy.