Hydatidiform mole is a conceptus, usually devoid of an intact fetus, with variable proliferation of trophoblast and altered placental
protein synthesis, including high
human chorionic gonadotropin (hCG) and low
human placental lactogen (hPL) production. Little is known about the control of the production of these two
placental proteins in
molar pregnancies. Regulatory
guanine 5'
triphosphate (
GTP)-binding proteins (
G proteins) play key roles in the endocrine control of
peptide production by the placenta. The present authors recently demonstrated that Gi2, Gi3 Go, and Gs alpha-subunits were expressed in normal human placenta throughout pregnancy. This study analysed the expression of placental
G protein alpha-subunits in
molar pregnancies. Western and Northern blot analyses were performed on
membrane protein and total
mRNA preparations of human placentae, respectively, from
hydatidiform mole (n = 5) and normal pregnancies (n = 4). The levels of hPL and beta-hCG mRNAs were 60 and 237 per cent respectively, of those from normal placentae. The autoradiographs for
G proteins and their mRNAs showed decreased expression in molar placentae in comparison with normal tissues. Specifically, G alpha i2, G alpha i3, G alpha o, and G alpha s levels reached 39, 4, 42, and 89 per cent, respectively, of those from normal placentae. In parallel with the
protein levels, their mRNAs expression were 8, 3, 54 and 65 per cent of normal values for G alpha i2, G alpha i3, G alpha o, and G alpha s, respectively. The results demonstrate important changes in placental
G protein expression in
hydatidiform moles suggesting alterations in the signal transduction machinery within the molar trophoblast.