Methylene blue enhanced photorelaxation in aorta, pulmonary artery and corpus cavernosum

Biochem Biophys Res Commun. 1993 Jan 29;190(2):559-63. doi: 10.1006/bbrc.1993.1084.

Abstract

Segments of endothelium-denuded pulmonary arterial and aortic rings and strips of corpus cavernosum from rabbits were superfused with Krebs solution alone and then Krebs medium containing 0.1-0.5 mM N omega-Nitro-L-Arginine. Photorelaxation in response to ultraviolet light (366 nm) was significantly enhanced by 50 microM methylene blue in all preparations; 25 microM methylene blue also increased photorelaxation in corpus cavernosum and pulmonary artery. Enhanced photorelaxation was associated with increased tissue cGMP. This effect was significantly attenuated by 10 microM hemoglobin and was associated with decreased tissue cGMP but was unaffected by superoxide dismutase. We speculate that UV-generated free radicals convert the phenothiazine moiety of methylene blue to a phenyl radical which activates guanylate cyclase and thus enhances smooth muscle relaxation.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Aorta / drug effects
  • Aorta / physiology
  • Arginine / analogs & derivatives
  • Arginine / pharmacology
  • Cyclic GMP / metabolism
  • Hemoglobins / pharmacology
  • Male
  • Methylene Blue / pharmacology*
  • Muscle Relaxation / drug effects
  • Muscle Relaxation / radiation effects
  • Muscle, Smooth, Vascular / drug effects*
  • Muscle, Smooth, Vascular / physiology
  • Nitroarginine
  • Penis / drug effects
  • Penis / physiology
  • Photosensitizing Agents / pharmacology*
  • Pulmonary Artery / drug effects
  • Pulmonary Artery / physiology
  • Rabbits
  • Ultraviolet Rays*

Substances

  • Hemoglobins
  • Photosensitizing Agents
  • Nitroarginine
  • Arginine
  • Cyclic GMP
  • Methylene Blue