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Photodynamic effects of erythrosine on the smooth muscle cells of guinea‐pig taenia coli
Author(s) -
Matthews E.K.,
Mesler D.E.
Publication year - 1984
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1984.tb16520.x
Subject(s) - erythrosine , taenia coli , chemistry , biophysics , egta , calcium , muscle contraction , contraction (grammar) , photodynamic therapy , biochemistry , biology , endocrinology , chromatography , organic chemistry
1 Photon activation of the halogenated fluorescein derivative erythrosine caused a marked calcium‐dependent contraction of the smooth muscle cells of the guinea‐pig taenia coli superfused in vitro . Neither high intensity illumination alone (up to 5 × 10 4 lux) nor erythrosine alone (up to 2 × 10 −4 M ) altered the tone of the taenia or its ability to respond to carbachol (5 × 10 −5 M ); photo‐irradiation of erythrosine before tissue contact was also ineffective. 2 The magnitude of the photodynamic contraction was dependent upon the concentration of erythrosine, the intensity and wavelength of the incident light, and the presence of oxygen; indirect effects via neurotransmitter release or cyclo‐oxygenase activation were specifically excluded. 3 The photodynamic response was blocked by zero‐[Ca] o and addition of EGTA (1 m M ) but not by omission of [Mg] o or a decrease in [Cl] o or [Na] o . D600 (methoxyverapamil) 10 −5 M , or a ten fold increase in [Mg] o , to 11.3 m M , partly inhibited the photodynamic contraction at low, but not high, light intensities. 4 These observations are consistent with the following sequence of events: (i) photo‐activation of the erythrosine molecule, (ii) the generation of highly reactive singlet oxygen, (iii) local peroxidation of cell membrane proteolipid, (iv) increased membrane permeability to Ca 2+ , (v) the influx of Ca 2+ and, (vi) muscle contraction. 5 It is concluded that the photodynamic action of erythrosine presents a novel method for modulation of membrane calcium permeability, and hence [Ca] i , not only in smooth muscle but possibly in other cells as well, e.g., secretory, epithelial and myocardial cells.