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This Article Full Text Full Text (PDF) All Versions of this Article: 89/4/343    most recent expphysiol.2003.026948v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Glass, C. A. Articles by Bates, D. O. Search for Related Content PubMed PubMed Citation Articles by Glass, C. A. Articles by Bates, D. O. Related Collections Vascular

Microvascular Research Laboratories, Department of Physiology, Preclinical Veterinary School, Southwell Street, University of Bristol, Bristol BS2 8EJ, UK

Microvascular permeability is regulated by changes in intracellular calcium concentration. The mechanism by which this increase in calcium determines permeability under normal conditions and during stimulation with agonists remains to be elucidated. In order to determine whether calcium release from intracellular stores could contribute towards the regulation of vascular permeability, hydraulic conductivity (L_p) was measured in frog mesenteric microvessels during stimulation of the endothelial cells of these vessels with agonists that release calcium from the intracellular stores. ATP (which acts through activation of inositol 1,4,5-trisphosphate (IP₃) receptors) increased L_p in the absence of calcium influx across the plasma membrane 2.3 ± 0.3 fold (mean ±S.E.M.., P < 0.01, n= 8), which was less than the increase in the presence of calcium influx (3.1 ± 1.1 fold). Caffeine (which acts through activation of ryanodine receptors) also increased L_p in the absence of calcium influx across the plasma membrane 3.8 ± 1.0 fold (P < 0.01, n= 9), but by at least as much as it does in the presence of calcium influx (2.8 ± 0.5 fold). It is surprising that there was a strong positive correlation between the size of the response during store release and the baseline permeability (r = 0.91 for ATP, r = 0.75 for caffeine). This suggests that the filling state of the stores may regulate the baseline permeability of the microvessels.

(Received 2 December 2003; accepted after revision 18 February 2003; first published online 16 March 2004)
Corresponding author D. Bates: Microvascular Research Laboratories, Department of Physiology, Preclinical Veterinary School, Southwell Street, University of Bristol, Bristol BS2 8EJ, UK. Email: dave.bates{at}bristol.ac.uk