Uptake of epinephrine by Hartmannella culbertsoni during differentiation

About half of the radioactivity of DL- [7-3H] epinephrine taken up by resting cells of axenically grown Hartmannella culbertsoni was reversibly bound to membraneous structures of amoeba. Propranolol inhibited the uptake of labelled epinerphrine and also reduced the extent of differentiation of tropic amoeba to viable cysts induced by epinephrine. Phontolamine did not show this activity. When a particulate fraction obtained by high speed centrifugation (100,000 g) of the homogenates of amoebae was first allowed to equilibriate with labelled DL-epinephrine, treated with dodecyl sulphate and then passed through a sephadex 75 column, radioactivity due to bound epinephrine was eluted with proteins immediately following the void volume of the column. (author)