Calcium Transport in the Microsomal Fraction of Rat Submandibular Glands

摘要

From previous studies, it has been concluded that the microsomal fraction from rate submandibular glands contains an ATP dependent calcium transport system. This thesis describes experiments directed at clarifying the function played by the system in salivary secretion. An effort was made to clarify the function of the transport system through characterization of the biochemical mechanism of transport. A series of experiments directed at understanding the role played by ATP in calcium transport is described. Either Mg or Mn was required for calcium accumulation with Mg being the more effective of the two. A series of experiments directed at determining the cellular location of the system is described. It was found that the membrane responsible for calcium transport did not copurify with the membrane vesicles, which contained the standard enzyme markers for endoplasmic reticulum, golgi complex, lysosomes, plasma membrane, mitochondria, and secretory granules. The significance of these results are discussed in terms of the insight they provide in (1) understanding the location of the calcium transporting membrane within the cell, (2) understanding the composition of the calcium transporting membrane, and (3) understanding the difficulties faced in organelle purification. Previous studies have suggested that the mechanism by which cAMP stimulates exocytosis is mediated through an intracellular calcium transport system, and a series of experiments directed at determining what effect cAMP may have on the microsomal calcium transport system are described. It was found that neither cAMP nor cAMP plus a cAMP dependent protein kinase (Sigma P5511) had any effect on the calcium transport properties of the microsomes. 73 references, 36 figures, 5 tables. (ERA citation 09:044595)