Contribution of potassium in human placental steroidogenesis.
The role of K(+) on steroidogenesis in isolated mitochondria from the human placenta was explored. Cholesterol uptake and progesterone synthesis were stimulated by K(+), and by the further addition of ATP. In the presence of glibenclamide or quinine (inhibitors of the K(+) channel mito-K(ATP)), the synthesis of progesterone was improved, indicating that K(+) acts outside the mitochondria. Valinomycin, a K(+)-ionophore, inhibited mitochondrial steroidogenesis only in the absence of K(+). The mitochondrial K(+) channel in human placental mitochondria is formed by the subunit Kir 6.1 which was detected by Western blot with polyclonal antibodies. These results suggest that K(+) contributes placental mitochondrial steroidogenesis facilitating cholesterol uptake and intermembrane translocation through a mechanism non-dependent of the transport of K(+) inside the mitochondria.
Milan
R
R
Department of Biochemistry, School of Medicine, National Autonomous University of Mexico, Mexico City, Mexico.
Flores-Herrera
O
O
Espinosa-Garcia
M T
MT
Olvera-Sanchez
S
S
Martinez
F
F
D015153:Blotting, Western; D002784:Cholesterol / Q000096:biosynthesis*; D005260:Female; D005905:Glyburide / Q000494:pharmacology; D006801:Humans; D007476:Ionophores / Q000494:pharmacology; D054086:KATP Channels / Q000037:antagonists & inhibitors / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism; D010920:Placenta / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D011247:Pregnancy; D011374:Progesterone / Q000096:biosynthesis*; D011803:Quinine / Q000494:pharmacology; D014634:Valinomycin / Q000494:pharmacology
D007476:Ionophores; D054086:KATP Channels; D014634:Valinomycin; D011374:Progesterone; D002784:Cholesterol; D011803:Quinine; D011188:Potassium; D005905:Glyburide