GUANOSINE 3':5'-CYCLIC MONOPHOSPHATE SOD (cGMP sodium salt) , also known as cGMP, is a cellular regulatory agent and has been described as a second messenger. Its levels increase in response to a variety of hormones, including acetylcholine, insulin, and oxytocin. GUANOSINE 3':5'-CYCLIC MONOPHOSPHATE SOD activates protein kinase G (PKG) and modulates ion channel conductance, with signaling affecting diverse processes including smooth muscle relaxation and proliferation, phototransduction, and energy homeostasis.