ISSN:
0021-9541
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
A dual effect of external Ca2+ on creatine kinase (CPK) accumulation during myogenesis has recently been demonstrated (Morris and Cole, '79). Ca2+ inhibits muscle-specific CPK accumulation at intermediate (50-100 μ) concentrations compared with both lower (no added Ca2+) and higher (2-3 μ) concentrations. Myoblast fusion, however, requires high Ca2+ and is inhibited at both low and intermediate Ca2+ levels.These effects are now investigated further by studying the effects of lanthanum ion (La3+), which interferes with Ca2+-binding to membranes and Ca2+-transport, and cytochalasin B, which affects the cell membrane and prevents cell fusion without inhibiting CPK accumulation.The results show that low concentrations (10-100 μ) of La3+ inhibit the appearance of the muscle-specific (MM) CPK isoenzyme during myogenesis without significantly affecting cell fusion or intracellular cyclic AMP levels. Three further observations are consistent with the existence of myotube-specific membrane-binding sites for Ca2+, which are involved in the stimulation of CPK accumulation on increasing external Ca2+ from intermediate to high concentrations.(1) CPK levels are not affected by La3+ at 0-50 μ external Ca2+.(2) CPK levels in cytochalasin B treated myoblasts are hardly affected by La3+ at any Ca2+ concentration.(3) In cytochalasin B treated cultures, CPK levels are not increased by raising external Ca2+ from intermediate to high levels.In contrast, the stimulation of CPK accumulation on decreasing external Ca2+ from intermediate to very low concentrations is not affected by either La3+ or cytochalasin B.Some alternative interpretations of the data are also considered, including direct disruption of a membrane Ca2+-binding site by cytochalasin B.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcp.1041050307
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