Enhancement of the transmesothelial resistance of the parietal sheep peritoneum by epinephrine in vitro: Ussing-type chamber experiments

The peritoneal mesothelium constitutes an ion transport barrier that is taken advantage of in peritoneal dialysis. The aim of this study was to investigate the effects of epinephrine on the electrical transmesothelial resistance (RTM) of the isolated parietal sheep peritoneum by means of Ussing-type chamber experiments. Intact parietal (diaphragmatic) peritoneal samples were obtained from adult sheep immediately after sacrifice and transferred within 0.5 h to the laboratory in a cooled Krebs-Ringer bicarbonate solution (4°C, pH 7.5), bubbled with 95% O2-5% CO2. A parietal peritoneal planar sheet was mounted in a Ussing-type chamber. Epinephrine (10-7 M) was added to the apical and the basolateral side. The RTM was measured before and serially after the addition of epinephrine for 30 min. As active ion transport is temperature-dependent, all measurements were performed at 37°C. The results were calculated as means with standard errors (x ± SE) of six independent experiments. The control RTM was 20.05 ± 0.61 Ω·cm2. The addition of epinephrine to the basolateral side within 1 min induced an increase of R TM to 21.8 ± 0.45 Ω·cm2, which decreased thereafter progressively to reach control values again after 15 min. A similar effect of epinephrine on the apical side was apparent with a rapid rise of RTM to 22.5 ± 0.66 Ω·cm2 and a subsequent decrease (P < 0.05). A clear association between the RTM and active ion transport was established from previous studies. The results of our study indicate a rapid action of epinephrine on the parietal peritoneum permeability

Permeability of the arachnoid and pia mater. The role of ion channels in the leptomeningeal physiology

Purpose: The purpose of this paper is to study the ionic permeability of the leptomeninges related to the effect of ouabain (sodium-potassium-ATPase inhibitor) and amiloride (epithelial sodium channel (ENaC) inhibitor) on the tissue, as well as identify the presence of ion channels. Methods: Cranial leptomeningeal samples from 26 adult sheep were isolated. Electrophysiological measurements were performed with Ussing system and transmembrane resistance values (RTM in Ω*cm2) obtained over time. Experiments were conducted with the application of ouabain 10-3 M or amiloride 10-5 M at the arachnoidal and pial sides. Immunohistochemical studies of leptomeningeal tissue were prepared with alpha-1 sodium-potassium-ATPase (ATP1A1), beta-ENaC, and delta-ENaC subunit antibodies. Results: The application of ouabain at the arachnoidal side raised the transmembrane resistance statistically significantly and thus decreased its ionic permeability. The addition of ouabain at the pial side led also to a significant but less profound increment in transmembrane resistance. The addition of amiloride at the arachnoidal or pial side did not produce any statistical significant change in the RTM from controls (p>0.05). Immunohistochemistry confirmed the presence of the ATP1A1 and beta- and delta-ENaC subunits at the leptomeninges. Conclusions: In summary, leptomeningeal tissue possesses sodium-potassium-ATPase and ENaC ion channels. The application of ouabain alters the ionic permeability of the leptomeninges thus reflecting the role of sodium-potassium-ATPase. Amiloride application did not alter the ionic permeability of leptomeninges possibly due to localization of ENaC channels towards the subarachnoid space, away from the experimental application sites. The above properties of the tissue could potentially be related to cerebrospinal fluid turnover at this interface. © 2012 Springer-Verlag

Role of Histamine in Altering Fluid Recycling in Normal and Post-Traumatic Rabbit Peritoneum

This study aims to investigate if histamine induces electrochemical alterations in the normal and post-traumatic peritoneum. Peritoneal rabbit specimens were obtained before surgery and 10 days post-operatively and were mounted in Ussing chambers. Histamine solutions were added facing the intra-peritoneal and outer-peritoneal surface. Dimetindene maleate-, cetirizine-, and ranitidine-pretreated specimens were used to investigate histamine receptor involvement, whereas amiloride- and ouabain-pretreated specimens were used to investigate ion transportation blockage involvement. Trans-mesothelial resistance (R (TM) ) was determined. Histamine-increased R (TM) intra-peritoneally and decreased it outer-peritoneally. A less intense effect was induced in post-traumatic specimens. Dimetindene maleate, cetirizine, amiloride, and ouabain totally inhibited this effect, whereas ranitidine only had a partial effect. Histamine induces electrochemical alterations in the normal and post-operative peritoneum. This effect is mediated by interaction with histamine receptors, hindering the normal process of ion trans-mesothelial transportation