Calcium paradox in skeletal muscles: physiologic and microscopic observations.
Immersion of rat hemidiaphragms in Ca2+-free Krebs solution (KS) containing Ca2+ chelator in vitro leads to separation of basal lamina from the plasma membrane, as well as transient contracture and rapid loss of twitch response [calcium paradox (CP) phase 1]. Subsequent immersion in regular KS results in necrosis of muscle fibers accompanied by slowly increasing contracture (CP phase 2). This contracture could be prevented or reduced by using either Ca2+-free KS or calcium channel blockers, but not by dantrolene sodium, implying that after drastic reduction of extracellular and sarcolemmal Ca2+ during CP phase 1, the sarcolemma has lost its ability to control normal Ca2+ fluxes. Contracture did not develop at 21 degrees C. CP is a convenient model to study calcium-induced muscle cell death and the role of Ca2+ in maintaining sarcolemmal integrity.
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D003964:Diaphragm / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D004492:Edetic Acid / Q000494:pharmacology; D005353:Fibronectins / Q000032:analysis; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects*; D007797:Laminin / Q000032:analysis; D008854:Microscopy, Electron; D009119:Muscle Contraction / Q000187:drug effects*; D009132:Muscles / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D051381:Rats; D011919:Rats, Inbred Strains; D012508:Sarcolemma / Q000648:ultrastructure
D005353:Fibronectins; D007797:Laminin; D004492:Edetic Acid; D002118:Calcium