Contribution of Potassium in Human Placental Steroidogenesis

Abstract 

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.

Keywords: Human placental mitochondria, Potassium, Cholesterol transport, Progesterone synthesis