KCNJ1 and Hyperkalemia: Kir1.1 mRNA is expressed in a specific group of ionocytes expressing ATP1A1a.4 (Abbas et al. 2011[1]), distinct from other ionocyte types (HR, NCC, and NaR ionocytes, see above); Kir1.1 loss-of-function was found to induce transient tachycardia followed by bradycardia (Abbas et al., 2011[1]), effects similar to those observed in hyperkalemia in human (Kahloon et al., 2005[88]).