Messenger ribonucleic acid levels of pregnancy-associated plasma protein-Aand the proform of eosinophil major basic protein: Expression in human reproductive and nonreproductive tissues

PAPP-A/proMBP, the complex of pregnancy-associated plasma protein-a (PAPP-A ) and the preform of eosinophil major basic protein (proMBP), circulates at increasing levels during pregnancy. The major site of synthesis is the pla centa, in which PAPP-A mRNA has been localized to the syncytiotrophoblast a nd the placental X cells, whereas proMBP mRNA has been localized to the pla cental X cells only. The function of PAPP-A/proMBP and its components has r emained speculative for years. Recently however, it has been shown that PAP P-A specifically cleaves insulin-like growth factor (ICF) binding protein-4 in an IGF-dependent manner. Female reproductive and nonreproductive tissue s have previously been reported to contain PAPP-A immunoreactivity, based o n studies using preparations of anti(PAPP-A/proMBP), now known to recognize both PAPP-A and proMBP, and other irrelevant antigens. To analyze for the presence of PAPP-A and proMBP mRNA, a sensitive semiquantitative reverse tr anscription (RT) polymerase chain reaction (PCR) method was developed. Reve rse-transcribed poly(A)(+) RNA was used as a template in a competitive PCR. PAPP-A and proMBP mRNA levels were normalized against the level of p-actin mRNA. Both mRNA species were significantly more abundant in term placenta than in other tissues analyzed. All analyzed tissues, including endometrium , myometrium, colon, and kidney, contained both PAPP-A and proMBP mRNA.