AUTOREGULATION OF BLOOD FLOW: EXAMINING THE PROCESS OF SCIENTIFIC DISCOVERY

Autoregulation of blood flow is the tendency for blood flow to remain constant in an organ during changes in arterial perfusion pressure. It is due to local mechanisms in the organ and is independent of the regulatory mechanisms of the central nervous system. The possible explanations that have received the most attention are the metabolic and myogenic hypotheses. We review the experimental evidence for and against these hypotheses both to develop our understanding of autoregulation and as examples of the process of scientific inquiry. Evidence is presented in support of the metabolic hypothesis that autoregulation is due to a link between blood flow and energy metabolism but the lack of definitive evidence for most proposed mediators is noted. The myogenic response has been more controversial since it proposes that the arterioles regulate flow indirectly by constricting in response to intravascular pressure as a stimulus. The possible involvement of integrins and stretch sensitive channels in this response is described. Autoregulation may be important in clinical situations such as atherosclerosis and blood loss. Reviewing the development of our understanding of autoregulation provides insight to the manner in which concepts arise and are tested experimentally.