. The high Na+ rinse was used to remove
any isotope adsorbed to the body surface of the fish. This rinse was
followed by a series of two distilled water rinses. Following spinal
cord transection to ensure complete euthanasia, fish were blotted
dry and weighed. Whole fish and water samples were measured
for radiolabelled Na+ incorporation via gamma counting (Wallac
Wizard 1470; Perkin Elmer). Water samples were analysed for Na+
via flame spectrophotometer (Sherwood Instruments). These values
were used to calculate specific activity (cpm M−1) before