The renin–angiotensin–aldosterone system: into the new millennium

Angiotensin Protocolsedited by Donna H. Wang. Humana Press, 2001, US$125.00 (xiv + 530 pages)ISBN 0896037630The renin–angiotensin–aldosterone system (RAAS), a multifunctional physiological system, has a central role in cardio- and cerebrovascular physiology. Over the past two decades, the contribution of the RAAS to human pathophysiology and its therapeutic modulation has been extensively investigated, largely by pharmacological means. In more recent years, many important advances in molecular genetics have taken place and the potential for further application of these techniques in the examination of physiological systems creates exciting opportunities. However, as indicated in the editor's preface to Angiotensin Protocols, ‘…there are great challenges in the integration of the attempts to close the gap between the traditional literature of medicine and the explosion of information from new technologies.’ The aim of this book was, therefore, to ‘…translate expert knowledge into easy-to-follow practice.’ With each chapter written by leading researchers who have made direct experimental contributions to their area, this objective is readily met.Angiotensin Protocols is a multi-authored book organized into 34 chapters and conveniently divided into seven sections. Its 530 pages provide an extensive, methodological how-to guide for investigating the RAAS at various levels of complexity, ranging from the molecular level to in vivo physiology. Applications of recent procedural advances in molecular biology and physiology to the RAAS are highlighted throughout the book.All chapters, with the exception of the first two of the introductory section, begin with a useful introduction to the technical procedures that follow, emphasizing major recent findings relevant to the RAAS. Each chapter then continues with a description of procedures, in a step-by-step easy-to-follow format. Particularly for anyone new to the procedure, most chapters follow the ‘Procedure’ pages with a very useful ‘Notes’ section that points out particular steps of the technique requiring special care and attention. All chapters end with an extensive and useful reference list of relevant literature. The similar layout of the chapters throughout the book (except for the introductory chapters), allows for easy reading and accessing of information.Angiotensin Protocols opens with an introductory section, which contains a historical perspective of the RAAS, beginning with its birth in 1898 and charting important developments in RAAS research over the 80 years that followed. The next chapter in this section provides an interesting history of the physiological role of angiotensins in the context of hypertension and renal haemodynamics, primarily from a clinical or patient viewpoint.The second section of the book encompasses four chapters on genetic manipulations of the RAAS in the whole animal. Molecular physiology is an exciting new area of molecular research, enabling investigators to examine specific molecular mechanisms underlying physiological processes. In this context, this section of the book is particularly impressive because it is both informative (with several useful internet sites) and clear, and makes good use of illustrations. Included here are details of how to produce chimeric mice, and the use of Cre-loxP recombinase for creating conditional knockout mice is demonstrated. In vivo gene and antisense delivery methods, including the use of retroviral and adenoviral vectors, are also discussed. The next section of the book deals with molecular genetic manipulations of the RAAS in in vitro systems. This group of chapters enables one to learn how to study gene expression at both the transcriptional and translational level, by making use of identification procedures for gene transcription factors. The electromobility shift assay and the wheat-germ extract system for examining angiotensin-receptor gene translation are clearly described.The fourth section of Angiotensin Protocols provides details on various methods, focusing specifically on mRNA measurements. Information on how to quantify AT1a and AT1b receptors using PCR can be found here, in addition to general procedures for northern blotting and in situ hybridization. The major focus of this section, however, is the ribonuclease protein assay (RPA), and a useful list of advantages and disadvantages of the RPA and northern blot analysis is provided, enabling researchers to avoid potential pitfalls. This is followed by a series of chapters that further detail various protein and enzyme-assay approaches to studying the RAAS. Although changes at the genetic level are obviously of potential importance, such modulations also need to be accompanied by altered activities and levels of proteins for there to be an influence on the all-important physiological function. Thus, in this section one can also find how to do a western blot to determine protein levels, to quantify angiotensin (I, II and III) peptides, and to perform receptor-binding assays.The penultimate section of the book discusses biochemical aspects of the RAAS and gives details of how to analyze various intracellular-signaling cascades activated by the RAAS. Methods to measure intracellular free calcium, phospholipase D, cAMP, cGMP, nitric oxide and renin are also described. The final and longest part of the book, encompassing nearly 100 pages, considers the role of the RAAS in physiological function. Half of this section is devoted to methods relevant to in vivo kidney function, such as laser Doppler flowmetry, and in vitro juxtamedullary nephron and tubular activity. Measurement techniques to assess microvessel density are also discussed, and these can of course be applied to any tissue of choice. The remainder of this section focuses on the vasoactive role of the RAAS in isolated resistance-sized and microcirculatory blood vessels. Some of the chapters in this section tend to overlap to some extent, so perhaps their integration might have been more appropriate.As a reviewer, I need to consider any limitations of the book. In this regard, perhaps a mention of recent evidence suggesting differences between human and rodent RAASs, particularly the existence of non-angiotensin converting enzyme-dependent mechanisms for angiotensin II generation 1xImplications of species difference for clinical investigation: studies on the renin–angiotensin system. Hollenberg, N.K. Hypertension. 2000; 35: 150–154Crossref | PubMedSee all References1 and the presence of non-AT1 and non-AT2 receptors 2xAtypical (non-AT1, non-AT2) angiotensin receptors. Smith, R.D. Adv. Exp. Med. Biol. 1996; 396: 237–245Crossref | PubMedSee all References2 would have been useful. On a methodological note, organ culture, a technique that allows whole segments of tissues to be studied chronically in tissue culture 3xPressure and angiotensin II synergistically induce aortic fibronectin expression in organ culture model of rabbit aorta. Evidence for a pressure-induced tissue renin–angiotensin system. Bardy, N. et al. Circ. Res. 1996; 79: 70–78Crossref | PubMedSee all References, 4xEffects of the endothelium on growth responses in arteries. De Mey, J.G. et al. J. Cardiovasc. Pharmacol. 1993; 21: S22–S25Crossref | PubMedSee all References, 5xAction of angiotensin II on DNA synthesis by human saphenous vein in organ culture. Ibrahim, J. et al. Hypertension. 2000; 36: 917–921Crossref | PubMedSee all References, might have been worthy of mention, particularly now that there is fairly good evidence for the existence of local tissue RAASs (Ref. 3xPressure and angiotensin II synergistically induce aortic fibronectin expression in organ culture model of rabbit aorta. Evidence for a pressure-induced tissue renin–angiotensin system. Bardy, N. et al. Circ. Res. 1996; 79: 70–78Crossref | PubMedSee all ReferencesRef. 3).In conclusion, this book makes for a good how-to reference guide to have in the laboratory. It is well referenced, and has a very useful index to most relevant keywords. The major strengths of the book are that it provides an easy step-by-step guide to enable one to follow a variety of experimental procedures. In particular, the ‘Notes’ section at the end of each chapter is likely to prove useful for anyone following a procedure for the first time, as it clearly lists the dos-and-don'ts pertinent to achieving successful experimental outcomes. Although most of the procedures are described in the context of the RAAS, they could equally be applied to other physiological systems. Thus, I would recommend this book to anyone interested in performing molecular or genetic experimental studies of the RAAS or other physiological systems, with expertise ranging from that of the uninitiated graduate student to that of established researchers. As for its value, although US$125 is somewhat expensive, the pages of Angiotensin Protocols provide extensive, up-to-date information in a concise, easy-to-read format.