In Vivo Evaluation of In Vitro Hypothesis Using “Gain or Loss” of Function: Functional Analysis of Renin-Angiotensin System

Characterization of the role of components of the renin angiotensin system (RAS) in vivo is limited by the difficulty in manipulating these individual components, as well as by methodologic limitations in studying the function of a local RAS in the absence of any contribution by the circulating RAS. In vivo gene transfer technology provides us with the opportunity to study the physiologic responses to in vivo manipulation of the individual components related to hypertension (ie, by overexpression or inhibition) without changes in the circulating system. Using this technology, the importance of each component of RAS in blood pressure regulation has recently been shown. Such an approach may increase our understanding of the biology and pathobiology of the autocrine-paracrine system in hypertension. This review discusses the potential utility of in vivo gene transfer methods.