Open AccessInositol 1,4,5-Trisphosphate- and Caffeine-Sensitive Ca2+-Storing Organelle in Bovine Adrenal Chromaffin Cells
Author(s) -
Hiroki Teraoka,
Ryo Takai,
Tetsuro Taneike,
Takeo Hiraga,
Akira Ohga
Publication year - 1996
Publication title -
japanese journal of pharmacology/japanese journal of pharmacology
Language(s) - English
Resource type - Journals
eISSN - 1347-3506
pISSN - 0021-5198
DOI - 10.1254/jjp.72.307
Subject(s) - endoplasmic reticulum , organelle , inositol , adrenal medulla , inositol trisphosphate , mitochondrion , biochemistry , microsome , caffeine , biology , chemistry , enzyme , endocrinology , receptor , catecholamine
The uptake and release properties of Ca2+ by several subcellular fractions of the bovine adrenal medulla were investigated. Investigation by the 45Ca2+ tracer method showed that permeabilized cells and the fractions of mitochondria (MT) and microsomes (MC) caused ATP-dependent Ca2+ uptake in a Ca2+ concentration-dependent manner (pCa 8-4), whereas permeabilized cells and the fractions of secretory granules (SG) were able to accumulate a significant amount of Ca2+ even in the absence of ATP, which was completed by the addition of hexokinase and glucose. In these organelle fractions, Ca2+ uptake in the presence of ATP at pCa 7 and pCa 5.8 was well-correlated with the activity of the NADPH cytochrome c reductase (marker enzyme for the endoplasmic reticulum) and cytochrome c oxidase (marker enzyme for mitochondria), respectively. As detected by Fura-2 ratiometry, both inositol 1,4,5-trisphosphate (IP3) and caffeine caused concentration-dependent Ca2+ releases from permeabilized cells and MC, but not from MT and SG. In an ATP-depleted condition, homogenates still took up a significant amount of Ca2+ but was not able to respond to IP3 and caffeine. These results suggest that the endoplasmic reticulum is a major Ca(2+)-storing organelle, which releases Ca2+ in response to IP3 and caffeine in bovine adrenal chromaffin cells.