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The calcium content of the smooth muscle of the guinea‐pig taenia coli
Author(s) -
Goodford P. J.
Publication year - 1967
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1967.sp008293
Subject(s) - calcium , chemistry , sodium , potassium , zoology , mole , phosphate , sorbitol , nuclear chemistry , mineralogy , biochemistry , biology , organic chemistry
1. The in vitro calcium content of the smooth muscle of the guinea‐pig taenia coli was 3·0 m‐mole Ca/kg wet wt. when phosphate was omitted from the bathing medium, and was almost independent of pH changes in the range 6·7‐7·6. 2. The calcium content was not changed when 1 m M phosphate was included in the medium, if the pH was 6·7 or 7·0. However, when the pH was 7·6, the calcium content increased by 1·5 m‐mole Ca/kg wet wt. in the presence of phosphate. 3. The calcium content rose by 1·1 m‐mole Ca/kg wet wt. when NaCl in the bathing medium was replaced by isotonic sucrose, and rose by 0·7 m‐mole Ca/kg wet wt. when MgCl 2 in the bathing medium was replaced. These increases may reflect a competition between Ca 2+ and other cations for fixed negative sites in the tissue. 4. The initial rapid phase of 42 K exchange corresponded to an ‘extra‐cellular 42 K‐space’ of 470 ml./kg fresh wt. in normal solution, rising to 560 ml./kg. fresh wt. in low‐sodium solution and to 760 ml./kg fresh wt. in calcium‐free low‐sodium solution. In this last medium the extra‐cellular [ 14 C]sorbitol space was only 390 ml./kg fresh wt., so that there was a large excess of rapidly‐exchanging potassium which may have been competing at fixed negative sites.