Evidence for rapid and concerted turnover of membrane phospholipids in MOPC 41 myeloma cells and its possible relationship to secretion.

Newly synthesized microsomal membrane phospholipids of actively secreting myeloma cells all appear to decay rapidly, with initial half-lives of less than 1 h. Their rates of decay are similar to each other and to the rates observed earlier for the decay of the protein components of the membrane and also for the intracellular turnover of immunoglobulin light chain, the predominant secretory product of these cells. This evidence, which suggests that many different components of the membrane and, therefore, presumably the membrane itself turn over rapidly, provides support for the hypothesis that unidirectional membrane flow, accompanied by rapid synthesis of the membranes at the origin of flow and their rapid degradation at or near the terminus of flow, is the mechanism of intracellular transport of secretory product by the myeloma cell. An attractive feature of this mechanism is that rapid synthesis and degradation of the membranes could provide the driving force for membrane flow.