UPTAKE OF VANADIUM BY THE ASCIDIAN ASCIDIA-CERATODES

1. The incorporation of vanadium from seawater into the plasma and blood cells of the phlebobranch ascidian Ascidia ceratodes has been investigated using the radioisotope V-48. 2. There are two paths by which vanadium enters the blood cells. One path, I, involves direct uptake from the plasma by the blood cells. 3. The other path, II, results in the long-term incorporation in the blood cells. 4. Possible mechanisms for II are: (a) the slow loss from remote sites into the plasma and then direct incorporation into blood cells or (b) incorporation during blood-cell production and development. 5. Studies of the exchange of V-48 between labelled plasma and unlabelled blood cells show that plasma and plasma simulants with in vitro added vanadium (V) are not good models for the in vivo uptake of vanadium by blood cells from plasma.