Fig. 7. Kinetics of endocytosis of ¹²⁵I-fluorescein–pDNA in cultured cod atrial endocardial endothelial cells at 12°C (A) and head kidney leukocytes at 6°C (B). Monolayer cultures of aEEC or head kidney leukocytes in 2 cm² wells were incubated with trace amounts of ¹²⁵I-fluorescein–pDNA (approximately 2x10⁴ c.p.m.; 20 ng). The results are presented as the cell-associated percentage of the total added radioactivity and are the mean of three independent experiments (aEEC). The result from the head kidney leucocyte study are the mean of cells from eight different fish.