RELATIONSHIPS BETWEEN THE NUCLEAR-MEMBRANE, NUCLEAR-PORE COMPLEXES, AND ORGANELLES IN THE TYPE-II PNEUMOCYTE

Functional relationships among organelles of the type II cell are sugg ested based upon the proximity of organelles to specialized areas of t he plasma- and nuclear membranes. In a two-dimensional morphometric an alysis of the profiles of organelles in type II cells of the ferret an d rat (and beagle dog), lamellar bodies were more likely to be located near the nuclear membrane than at the alveolar space (where exocytosi s occurs). The size of lamellar body profiles was not correlated with distance from the nuclear membrane; however, large profiles were neare r the apical membrane, and smaller ones nearer the basement membrane. Profiles of highly branched mitochondria were 10 times more frequently associated with nuclear pore complexes than with the inter-pore nucle ar membrane. Forty percent of all mitochondrial profiles were within 0 .25 mu m of the nucleus, 5% were within 0.02 mu m and half of these ap peared to touch the filaments of the nuclear pore complexes. The size of mitochondrial profiles was not correlated with distribution. In the ferret and rat, 8.6% and 2.5% respectively, of the nuclear pore compl exes were associated with mitochondria. Sebaceous cells, from control mice, demonstrated a spatial distribution of granules which was size d ependent but unrelated to the nuclear membrane.