Possible involvement of actin and myosin in Ca2+ transport through the plasma membrane of chromaffin cells.
The exocytosis of catecholamines by chromaffin cells following stimulation (e.g. by acetylcholine) is accompanied by a rise in the level of intracellular free Ca2+. Actually, secretion can be induced merely by making the cells leaky to Ca2+ from the external medium. We have recently demonstrated that secretion can be increased by the introduction of DNase-I, the F-actin depolymerizing agent, or of heavy meromyosin, the enzymatically active fragment of myosin. Suspecting that these changes might be associated with a higher intracellular level of Ca2+, we now have measured the influx of 45Ca2+ into chromaffin cells which have undergone fusion with DNase-I- or with heavy meromyosin-loaded liposomes. In both cases, a marked increase in Ca2+ uptake has been observed, which could be abolished by Co2+ ions (a Ca2+ channel blocker), suggesting an intimate involvement of the cellular actomyosin system in the process of Ca2+ ions transport through the Ca2+ channels of the plasma membrane.
D000199:Actins / Q000378:metabolism*; D000313:Adrenal Medulla / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D002837:Chromaffin Granules / Q000378:metabolism; D005089:Exocytosis; D007700:Kinetics; D008081:Liposomes; D009218:Myosins / Q000378:metabolism*
D000199:Actins; D008081:Liposomes; D009218:Myosins; D002118:Calcium