GCH1 and septic shock: Although deficiency in endothelial cell Gch1 and BH4 protects against LPS-induced vascular dysfunction and hypotension in Gch1fl/flTie2cre mice using this non-lethal LPS dosing regimen, it is unknown whether deficiency in endothelial cell Gch1 and BH4 biosynthesis is protective against endotoxaemia caused by LPS at higher doses or during septic shock in vivo.