Gossypol-induced damage to mitochondria of transformed Sertoli cells

Studies on gossypol-induced morphologic changes in transformed Sertoli cells (TM4) were performed at both light- and electron-microscopic levels. Exposure of TM4 cells to 5 micrograms gossypol/ml for greater than 1 hour has severe, deleterious effects on the structure and function of mitochondria. Mitochondrial function in TM4 cells was monitored by employing a fluorochrome, Rhodamine 123, which accumulates rapidly in mitochondria having a high transmembrane potential. In gossypol-treated TM4 cells, Rhodamine 123 mitochondrial staining was reduced significantly 1 hour after the drug addition and reached a minimal level at 3 hour. Concomitantly, cytoplasmic vacuoles were detected even at the light-microscopic level. Electron-microscopic studies revealed that these vacuoles were distended mitochondria. The morphology of these damaged organelles changed gradually, starting with the transformation of the tubular mitochondria into the rounded forms. Cristae concurrently collapsed onto the organelles' periphery. In addition, the ground matrixes disappeared, and the mitochondria appeared as empty vacuoles. Further evidence that these vacuoles were distended mitochondria was derived from the cytochemical localization of cytochrome c oxidase in these vacuole-like structures.