Influences of exercise-stress and adrenaline upon intra- and extracellular acid-base status, electrolyte composition and respiratory properties of blood in tench (Tinca tinca) at different seasons.

Exercise-stress in tench resulted in severe acidosis in both the red cells and the extracellular fluid in vivo. These coincident pH decreases conformed to the in vitro pHi-pHe relationship for tench blood in the oxygenated state. The extracellular acidosis was primarily respiratory in winter and metabolic in spring and summer. This was due to more effective buffering of metabolic protons in winter by an elevation in [HCO3-] levels, rather than to differences in the lactic- and carbonic acid loads. A good correspondence was found between buffered metabolic protons and increases in [lactate]. There was no evidence for beta-adrenergic red cell swelling and associated red cell pH changes in tench both after exercise and adrenaline infusion. Arterial O2 transport was, however, improved in exercise by pronounced increases in PO2. This increase was not of adrenergic origin, as adrenaline alone caused a decrease in arterial PO2. Large increases in plasma potassium concentration and small elevations of chloride and calcium levels occurred in exercise. Hematocrit and blood [Hb] also increased, probably due to an adrenergic release of erythrocytes from the spleen, but these increases were small and appeared unimportant for blood O2 transport. Seasonal differences were found in exercise-induced changes in [lactate], in the magnitude of electrolyte and PO2 changes, as well as in resting values for pHe, pHi, [HCO3-], [Cl-] and [Ca++]. The origin and importance of these are discussed.