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1982 (1)
1Author    L. RaeymaekersRequires cookie*
 Title    The Sarcoplasmic Reticulum of Smooth M uscle Fibers  
 Abstract    The ability of the sarcoplasm ic (endoplasmic) reticulum (SR, ER) of smooth muscle cells to accumulate Ca was dem onstrated by measuring the uptake of 45Ca in fibers which were chemically skinned with saponin, and by electron cytochemistry of the accum ulated Ca. The Ca uptake was dependent on ATP and it was stim ulated by oxalate, as it is the case in SR of striated muscle. Electron microscopy of the skinned smooth muscle preparations revealed the presence o f calcium oxalate deposits in the reticulum . The SR vesicles were isolated from several sm ooth muscles. The purification was carried out by taking advantage o f the density increase o f the SR vesicles after loading with calcium in the presence of oxalate. Among the muscles investigated the smooth muscle of the pig stomach was found to be the most suitable and it was selected for further biochem ical and m orphological characterization of the SR vesicles. These vesicles, which contain calcium oxalate crystals, were able to accumulate an additional am ount of Ca. The Ca uptake was supported by several energy yielding substrates. T h eir order o f potency was ATP > dATP ~ U TP > ITP > G TP ~ CTP. The rate of Ca uptake was two orders o f m agnitude slower than that in SR of skeletal muscle. The measurement of the level o f phosphorylated Ca transport interm ediate showed that this difference is due to smaller num ber of calcium transport sites per vesicle. The distribution o f intram em ­ brane particles in freeze-fractured specimens is in agreem ent with this conclusion. 
  Reference    Z. Naturforsch. 37c, 481—488 (1982); received January 25 1982 
  Published    1982 
  Keywords    Smooth Muscle, Microsomes, Sarcoplasmic Reticulum, Calcium Metabolism, Electron Microscopy 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-0481.pdf 
 Identifier    ZNC-1982-37c-0481 
 Volume    37