Bay K 8644 induced necrosis in murine skeletal muscle in vitro: myofibre breakdown precedes significant alterations of intracellular [Ca] or pH.

Abstract

The effect of the Ca2+-channel agonist Bay K 8644 (1 mumol/l) on the ultrastructure, Ca2+-homeostasis, pH and membrane potential of murine diaphragm muscle, in vitro, has been investigated. Treatment with Bay K 8644 in a standard physiological saline, for 1-2 h, induced swelling of the muscle mitochondria and minor damage to the myofibrils. Ultrastructural Ca-localisation by antimonate precipitation revealed no differences between treated and control preparations. Accompanying the structural changes there was a small, non-significant increase in muscle Ca content. In EGTA-buffered (Ca-free) standard saline the induction of damage was not inhibited. When [K+]o was raised to 20 mmol/l, a procedure that approximately halved the resting potential, Bay K 8644 induced severe ultrastructural damage within 1 h, and complete cellular necrosis within 2 h. Induction of myopathy was unaffected by synaptic blockade (150 mumol/l D-tubocurarine). Necrosis was accompanied by depolarisation of membrane potential (Em) and increased antimonate precipitation in the sarcoplasm, and was abolished by buffering of [Ca2+]o with EGTA. However, muscles did not develop tension and measurements of both total Ca and [Ca2+]i suggest that cellular Ca2+ buffering was not seriously impaired until 2 h after Bay K 8644 application. Measurement of sarcoplasmic pH revealed no significant change during fibre necrosis. It is proposed that in partially depolarised preparations Bay K 8644 acts on a Ca2+-channels in the cell membrane, probably the T-tubules, to induce muscle necrosis through enhanced influx of Ca2+. However, muscle necrosis occurs before significant elevation of [Ca2+]i and does not require sarcoplasmic acidification.

• Authors: J D Howl, S J Publicover
• Journal: Acta neuropathologica (Acta Neuropathol) Vol. 77 Issue 6 Pg. 634-44 ( 1989) ISSN: 0001-6322 [Print] Germany
• PMID: 2473591 (Publication Type: Journal Article)

Chemical References

• 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester
• Calcium

Topics

• 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester (pharmacology)
• Animals
• Calcium (metabolism, physiology)
• Diaphragm (drug effects, physiology, ultrastructure)
• Female
• Hydrogen-Ion Concentration
• In Vitro Techniques
• Male
• Mice
• Muscle Contraction (drug effects)