The involvement of pH, Adenosine triphosphate, calcium, and magnesium in the contraction of the glycerinated stalks of Vorticella

✍ Scribed by Townes, Mary M. ;Brown, Dugald E. S.

• Publisher: Wiley (John Wiley & Sons)
• Year: 1965
• Tongue: English
• Weight: 648 KB
• Volume: 65
• Category: Article
• ISSN: 0095-9898
• DOI: 10.1002/jcp.1030650214

✦ Synopsis

A glycerinated Vorticella stalk is prepared which remains relaxed at pH 6.8 or lower but contracts maximally when the pH is raised from 6.8 to 7.0. At pH 6.8, a maximum contraction is also produced when the Ca++ concentration is iacreased to 3 ,u M.

The degree of relaxation below pH 6.8 is fostered by ATP and Mg+ + which, along with C a + + , determine the degree of contraction at pH 7.0. A major role of calcium on the pH-induced contraction is to lower the pH-threshold from pH 7.5, obtaining in its absence to a stable value of pH 6.8. The only condition in which ATP is shown to cause a maximum contraction is at pH 7.0 in a medium containing 6 X M Mg++ and 3 X Ca++. It is considered that Ca++, Mg++, and ATP react with the contractile proteins to form a contractile complex which is in the relaxed form at pH 6.8. At this pH an increase of 0.2 pH units or the addition of shortened form, a contraction ensuing.