Methodological Approaches and Problems

Abstract

Body fluids of all animals contain similar buffer substances, the most important of which are bicarbonate and protein anions. Since acid-base-relevant by-products of cell metabolism can always be classified as volatile acid (CO₂) and fixed acids and bases, CO₂ and SID titrations of these fluids may occur and the general principles outlined in Chapter 1 must thus apply in all animal acid-base systems. However, well-established methodologies and usual concepts derived from mammalian acid-base physiology are not always directly applicable to lower animals, especially water-dwelling species, for a number of reasons. The range of values for acid-base variables may largely outstrip that found in mammals, which raises measurement problems. Many complications also arise from the fact that acid-base systems work under more variable physicochemical conditions in lower animals than in homeothermic vertebrates. The aim of the present chapter is thus to comment on particular applications of general acid-base methodologies and to describe some newly developed approaches to specific acid-base problems in lower animals.