title: Regulation of ion permeability in frog brain venules. Significance of calcium, cyclic nucleotides and protein kinase C.
abstract: 1. The effect on ionic permeability of frog brain endothelium of various second messengers was studied by a technique based on continuous recording of the electrical resistance of the venular endothelium in vivo. 2. Augmentation of the cytosolic Ca2+ concentration in endothelial cells induced with the ionophores ETH 1001 and A23187 increased ion permeability significantly as reflected in the reduced electrical resistance. 3. The electrical resistance fell reversibly within 1-2 s after administration of Ca2+-activating agents. The maximal effect was a reduction to about 0.70 times the pre-experimental resistance value. The resistance decrease was similar to that induced by several inflammatory mediators (Olesen & Crone, 1986). 4. Administration of the following agents did not change the electrical wall resistance: 8-bromo-cyclic AMP, dibutyryl-cyclic AMP, forskolin, 8-bromo-cyclic GMP, dibutyryl-cyclic GMP, sodium nitroprusside, phorbol myristate acetate (a protein kinase C stimulator). Changes in cytosolic Mg2+ did not affect permeability. 5. Ca2+ may be an important cytosolic signal in the endothelial cell, acting as an intracellular mediator for several permeability-augmenting substances.
mesh_terms: D000818:Animals; D001921:Brain / Q000098:blood supply*; D002118:Calcium / Q000378:metabolism*; D002199:Capillary Permeability / Q000187:drug effects*; D004553:Electric Conductivity; D004727:Endothelium / Q000502:physiology*; D007476:Ionophores / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D009712:Nucleotides, Cyclic / Q000494:pharmacology*; D011896:Rana temporaria; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014699:Venules / Q000502:physiology
chemical_list: D007476:Ionophores; D009712:Nucleotides, Cyclic; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium