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THE EFFECTS OF IONOPHORE A23187 ON PERMEABILITY OF THE FROG MESENTERY MICROVASCULATURE
Author(s) -
Michel C. C.,
Phillips Mary E.
Publication year - 1989
Publication title -
quarterly journal of experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0144-8757
DOI - 10.1113/expphysiol.1989.sp003241
Subject(s) - ionophore , pi , biophysics , chemistry , permeability (electromagnetism) , divalent , ficoll , bovine serum albumin , mesenteries , calcium , anatomy , biochemistry , biology , in vitro , membrane , peripheral blood mononuclear cell , organic chemistry
The effects of the divalent cation ionophore A23187, upon microvascular permeability have been investigated in single perfused capillaries and venules in the mesenteries of pithed frogs. In all experiments, the vessels were perfused with Ringer solutions containing the macromolecules Ficoll 70 (40 mg ml−1) and bovine serum albumin (10 mg ml −1 ). Hydraulic permeability ( L p ) of the vessel walls and the effective osmotic pressure (σΔπ) exerted across them by the perfusate macromolecules were estimated by the method of Michel (1980). In eleven experiments addition of A23187 to the perfusate raised L p from a mean value (± S.E.M.) of 4·76 (± 1·05) x 10 −7 cm s −1 cmH 2 O −1 to one of 11·97 (± 1·96) x 10 −7 cm s −1 cmH 2 O −1 and reduced σΔπ from a mean (± S.E.M.) of 16·5 (± 2·01) cmH 2 O to one of 7·6 (± 1·93) cmH 2 O. The effects of A23187 on L p and σΔπ were reversible. A23187 was found to increase L p and reduce σΔπ after the mesentery had been exposed to compound 48/80 to degranulate the mast cells two or more hours previously. A23187 also appeared to be effective in raising L p and lowering σΔπ in the absence of Ca 2+ ions from the perfusate and superfusate. The ionophore was found to reduce permeability, however, when Mg 2+ ions were removed from the perfusate and superfusate both in the absence and in the presence of Ca 2+ . This reduction in permeability could be converted into an increase in L p and fall in σΔπ if Mg 2+ were restored to the superfusate. It is concluded that A23187 increases vascular permeability in a reversible manner and that Mg 2+ ions in the extracellular fluids are necessary for its action.