However, while acute β2-AR activation is a potent inhibitor of collagen synthesis in healthy CFs, myofibroblasts isolated from patients with HF appear to be resistant to β2-AR agonists, most likely because of receptor uncoupling as a result of elevated GPCR kinase 2 (GRK2) activity (42–44). The gene discussed is ADRB2; the disease is hydrops fetalis.