Time resolved study of effect of chlorpromazine on mobility of cytochrome P-450 and phospholipids in the inner membrane of adrenocortical mitochondria

Isolation of rat adrenocortical mitochondria

This report describes a relatively simple and reliable method for isolating adrenocortical mitochondria from rats in good, reasonably pure yield. These organelles, which heretofore have been unobtainable in isolated form from small laboratory animals, are now readily accessible. A high degree of mitochondrial purity is shown by the electron micrographs, as well as the structural integrity of each mitochondrion. That these organelles have retained their functional integrity is shown by their high respiratory control ratios. In general, the biochemical performance of these adrenal cortical mitochondria closely mirrors that of typical hepatic or cardiac mitochondria.

Different pathways of degradation of SP-A and saturated phosphatidylcholine by alveolar macrophages

Alveolar macrophages degrade surfactant protein (SP) A and saturated phosphatidycholine [dipalmitoylphosphatidylcholine (DPPC)]. To clarify this process, using rabbit alveolar macrophages, we analyzed the effect of drugs known to affect phagocytosis, pinocytosis, clathrin-mediated uptake, caveolae, the cytoskeleton, lysosomal pH, protein kinase C, and phosphatidylinositol 3-kinase (PI3K) on the degradation of SP-A and DPPC. We found the following: 1) SP-A binds to the plasma membrane, is rapidly internalized, and then moves toward degradative compartments. Uptake could be clathrin mediated, whereas phagocytosis, pinocytosis, or the use of caveolae are less likely. An intact cytoskeleton and an acidic milieu are necessary for the degradation of SP-A. 2) Stimulation of protein kinase C increases the degradation of SP-A. 3) PI3K influences the degradation of SP-A by regulating both the speed of internalization and subsequent intracellular steps, but its inhibition does not prevent SP-A from reaching the lysosomal compartment. 4) The degradation of DPPC is unaffected by most of the treatments able to influence the degradation of SP-A. Thus it appears that DPPC is degraded by alveolar macrophages through mechanisms very different from those utilized for the degradation of SP-A.