Free And Total Calcium Concentrations in the Blood of Rainbow Trout, Salmo Gairdneri, During ‘Stress’ Conditions

Measurements were made of the free and total calcium concentrations ([Ca2−] and Cat), acid-base status, haemoglobin concentration, haematocrit and plasma protein concentration in the blood of the rainbow trout, Salmo gairdneri. In isolated blood, [Ca2+] was proportional to Cat while log[Ca2+] was inversely proportional to pH. Similar findings have been reported from human blood. During intense activity, [Ca2+] increased by 16% without any significant change in Cat. Neither sustained exercise, hypercapnic acidosis nor hypoxia affected [Ca2+] or Cat. These data indicate that during common natural stress conditions [Ca2+] is maintained within a narrow range.