Inhibin subunits mRNA expression level in human placenta from normal and Down's syndrome pregnancies

In order to study the mechanisms leading to increased inhibin A and activin A in maternal serum with advancing gestation and increased inhibin A in Do wn's syndrome pregnancy, the mRNA expression level of inhibin and activin s ubunits was quantitatively studied in human placenta using Northern blot an d semiquantitative RT-PCR analysis. The corresponding protein level was als o determined by specific ELISAs for inhibin A, inhibin B, activin A and inh ibin pro alphaC in placental extracts. Normal placenta (n = 27) showed a sl ight significant increase in alpha and betaA subunit mRNA levels in term pr egnancy, with no change of the corresponding protein level. Placenta from D own's syndrome pregnancies (n = 6) did not differ from controls in either m RNA expression or corresponding protein levels. In conclusion, there is a d issociation between inhibin and activin subunit mRNA levels and the corresp onding protein levels in maternal serum, and Down's syndrome inhibin A incr ease is not explained by mRNA expression upregulation. In an additional stu dy, ovarian cortex tissue from term pregnancies (n = 3) were examined. Only the a subunit mRNA was expressed, at a higher level than in the placenta, suggesting that ovary could be a source of inhibin pm aC during pregnancy.( C) 2001 Harcourt Publishers Ltd.