Nonlethal gamma radiation displays similar cytoplasmic rearrangements as 12(S)-HETE

Timar et al. (Int. J. Canc., 52:594-603, 1992) and Onoda et al. (Rad. Res., 130:281-288, 1992) implicated 12(S)-HETE and nonlethal gamma radiation respectively, in enhanced expression of the alpha IIb beta 3 integrin receptor in B16a tumor cells. 12(S)-HETE has been reported to induce rearrangement of cytoplasmic elements and movement of cytoplasm (Haddad and Taylor, Proc. Amer. Cancer Res., 34:51, 1993); Timar et al., Cell Motil. Cytoskel., 26:49-65, 1993). Here, we report similar results in B16a tumor cells by post 90 cGy gamma radiation. Control cells were circular without cytoplasmic processes with the majority of their organelles and elements in perinuclear regions both surrounded by a ring of actin microfilaments. The cell's extensive leading edge was organelle free with the exception of occasional endoplasmic reticular cisternae parallel to one or two microtubules, and short bundles of actin microfilaments perpendicular to the plasma membrane. As early as 5 sec, but better defined by 60-90 sec, one end of elongated microfilaments bundles became associated with the plasma membrane while the other end of the bundles became associated with perinuclear mass protrusions. By 5 min, prominent by 15 min, protrusions, now separated from the leading edge by mixture of bundle and ring microfilaments, reached the plasma membrane to form cellular processes. By 30 min, some cytoplasmic masses showed signs of retraction along with the disappearance of their associated mixed microfilaments. As well as numerous vesicles of unknown origin, primarily associated with microtubules perpendicular to the plasma membrane, mitochondria and endoplasmic reticular cisternae were found in the cytoplasmic masses.