Introduction

Since its introduction 40 years ago by E.C. Black and colleagues (Black, 1958; Black et al., 1962), the exhaustively exercised rainbow trout has proven a popular model in fish exercise physiology. To date, there are well over 200 papers on this system, and progress has been reviewed at regular intervals (Driedzic & Hochachka, 1978; Wood & Perry, 1985; Wood, 1991; Moyes, Schulte & Hochachka, 1993; Moyes & West, 1995; Weber & Haman, 1996; Milligan, 1996). It is not the intention in this chapter to recap this extensive literature again, but rather to focus on several specific issues. Firstly, in keeping with the theme of this volume, methodology is assessed – specifically, how should blood and white muscle samples be taken, and how should they be processed and analysed so as to represent most faithfully the metabolic and acid–base status existing in vivo? Secondly, the major post-exercise responses in this model system are briefly described, emphasising those studies in which the best methodology has been employed. Thirdly, several theoretical issues or ‘problems’ of current understanding are described, one of which constitutes the focus of the remainder of this chapter – specifically, what mechanisms determine the distribution and movement of ammonia, lactate, and protons between the intracellular fluid of white muscle and blood plasma of rainbow trout at rest and after exhaustive exercise? Fourthly, a new in vitro preparation is described, the isolated–perfused tail-trunk, which we have developed to investigate these problems. Lastly, recent findings are summarized, based on both this preparation and in vivo studies, which cast new light on these topics.