The Origin of Adrenal Cortical Mitochondria and Liposomes: a Preliminary Report

The origin of the lipide droplets or liposomes of the adrenal cortex has been the subject of controversy among cytologists for many years.Mulon (14) and Celestino da Costa (2, 3) suggested that they were derived from mitochondria by a direct transformation. Miller and Riddle (13) and Knouff and Hartman (7) have observed that mitochondria and liposomes of the adrenal cortex of birds are present in inverse proportions; Cowdry (4) made a similar observation concerning neurons as far back as 1914. While this gives indirect support to the concept of transformation, Knouff and I-Iartman considered such a transformation unlikely in the adrenal cortex. Hoerr (5), in denyins the concept of a direct transformation, stated that the appearance of mitochondria with lipide in their centers was due to faulty technique. An approach utilizing the high resolving power of the electron microscope should be a means of settling this problem, since mitochondria can be identiffed so readily with that instrument (16, 17, 20), even though in the adrenal cortex and certain other steroid secretors the mitochondria present a slight variation of the basic plan (1, 8--10). While Lever (8, 10), following an electron microscopic study of the adrenal cortex, has reported that mitochondria do transform into llposomes, the conclusions do not seem completely justified in the light of this author's findings. I t has long been known that mitochondria of cells in tissue culture may arise by fission of existhag mitochondria, and that they also fuse during their constant motion (11). Miller (12), by examining fixed preparations of adrenal cortex with the light microscope, found that mitochondria elongate and apparently divide following stimulation with ACTH or epinephrine. In electron micrographs of rat liver, Fawcett (5) showed mitochondria with an appearance suggestive of fission. In the liver of