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Effect of dinitrophenol and anoxia on isometric tension in rabbit colon smooth muscle.

Abstract
In a previous study, it was suggested that inhibition of oxidative phosphorylation in smooth muscle is accompanied by a release of Ca2+ from mitochondria (Pettersson 1983); in this investigation, the effects of 2,4-dinitrophenol (DNP) and anoxia on isometric tension in pieces of smooth muscle from rabbit colon were studied. Addition of DNP to the bathing medium elicited a transient and dose-dependent contraction with an ED50 value of 2 X 10(-4) M. The contraction was not inhibited by pretreatment with atropine (1 X 10(-6) M). The removal of external Ca2+ did not reduce the contracting action of DNP. Addition of the local anaesthetic D-mepivacaine (1 X 10(-3) M), which reduces the Ca2+ efflux through the plasma membrane of the smooth muscle cells, augmented the response to DNP. Gassing the bathing medium with 95% N2 + 5% CO2 (anoxia) for 60 min. did not affect the basal tension, but markedly reduced the contractile response to DNP. The results indicate that DNP increased cytoplasmic Ca2+ significantly enough to induce a contraction of rabbit colon smooth muscle by a large release from an intracellular store, probably from the mitochondria. Since anoxia did not mimic the contracting action of DNP, it is suggested that a high concentration of DNP would be a more effective stimulus for mitochondrial Ca2+ release than anoxia.
AuthorsG Pettersson
JournalActa pharmacologica et toxicologica (Acta Pharmacol Toxicol (Copenh)) Vol. 57 Issue 3 Pg. 184-9 (Sep 1985) ISSN: 0001-6683 [Print] Denmark
PMID4061099 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Dinitrophenols
  • Mepivacaine
  • Oxygen
  • Calcium
Topics
  • Animals
  • Calcium (metabolism)
  • Colon (drug effects)
  • Dinitrophenols (pharmacology)
  • In Vitro Techniques
  • Isometric Contraction (drug effects)
  • Mepivacaine (pharmacology)
  • Muscle, Smooth (drug effects)
  • Oxygen (pharmacology)
  • Rabbits

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