Abstract
Several low molecular weight compounds are capable of activating soluble guanylyl cyclase. Recent evidence suggests that some of these are formed under physiological conditions: the nitric oxide radical, carbon monoxide and the hydroxyl radical. Thus, multiple signal transduction pathways appear to exist that form a family of guanylyl cyclase activating factors and thereby regulate the intracellular cyclic guanosine 3′, 5′‐monophosphate level.