Structural changes in murine cancer associated with hyperthermia and lidocaine.

Hyperthermia alone and hyperthermia with lidocaine cause changes in the fine structure of the CA755 tumor cell as well as the breakdown of the tumor vasculature. The first structural change, observed immediately after termination of hyperthermia of 43.5 degrees for 1 hr, is the vesiculation of the Golgi apparatus. Other structural changes occur later but with variable times of onset. The changes appear to be unrelated to the presence of lidocaine. Vascular breakdown results in hemorrhaging within the tumor, and its onset and intensity appear to vary directly with the size of the tumor. Breakdown of the tumor cell plasmalemma and degenerative changes of the cytoplasm and nucleoplasm are seen more frequently in large tumors and in the interior of small tumors at any given time after the end of hyperthermia. The vesiculation of the Golgi persists in treated cells for as long as 30 hr. This modification may represent an intensification in the function of the Golgi apparatus; however, it closely corresponds to that found in a variety of other cells treated with a class of compounds, including lidocaine, that specifically inhibits the function of the Golgi apparatus. The effect of these compounds is rapidly reversible, unlike hyperthermia. Since the Golgi apparatus probably is crucial in repairing any deleterious effects of hyperthermia, any impairment of its normal function would place most treated tumor cells in a difficult position. The rate of tumor destruction may ultimately depend on the breakdown of the tumor vasculature following hyperthermia and lidocaine.