The document discusses various methods and concepts related to measuring permeability across epithelial tissues, including the following key points: - Short-circuit current (Isc) measures the sum of all active ion transport processes when the transepithelial potential is clamped to 0 mV. It provides information about epithelial function but is an unphysiological measurement. - Electrical resistance (Rt) and open-circuit voltage (Vt) measurements can also be used to determine ion movement and epithelial function without short-circuiting the paracellular pathway. - Tight junctions can vary in permeability between epithelia (tight vs leaky) and selectivity based on claudin composition, acting as aqueous pores or sie

1. An Introduction to the Shunt or Intercellular Pathway

2. Requests for Paracellular Presentation

6. The Intercellular Pathway Intercellular Pathway Intracellular Pathway

8. Diamond, JM and Bossert, WH, J Cell Biol. 1968. 37:694-702. Jared Diamond Ultrastructural Geometry in backwards fluid transporting epithelia “ Many fluid transporting epithelia posses dead-end long and narrow channels”

9. Jared Diamond Pulitzer Prize Winning Author

12. Electrical Resistances of Various Epithelia Powell, DW. 1981.Am. J. Physiol. 4: G275-G288.

15. Introduction to Leaky Epithelia 1982

16. Introduction to Leaky Epithelia

17. Introduction to Leaky Epithelia

19. Intracellular and Intercellular routes Powell, DW. 1981.Am. J. Physiol. 4: G275-G288.

25. 1970 The Paracellular Pathway

26. The Paracellular Pathway 1970

27. The Paracellular Pathway 1970 Emile Boulpaep

28. Advances that shaped the field

29. Studying the Tight Junction

33. Studying the Tight Junction

34. Paracellular flux V m Na + Cl - + -

35. Na + Cl - + 0 Simplified Ussing Chamber Technique Measure Δ I

36. Devor et al., J Gen. Physiol. 1999. 113:743-760. Methods for measuring R T Short-circuit current Isc measurements with voltage deflections of ± 2mV.

37. MacVinish et al., Br. J. Pharmacol. 2007. e-pub ahead of print Methods for measuring R T Short-circuit current Isc measurements with a voltage deflection of 1mV.

38. Grahammer et al., J Biol. Chem. 2001. 276:42268-42275. Methods for measuring R T Open-circuit V T measurements with current injections of 0.5 µ A

39. Current-Voltage relationship in a leaky epithelia Na + Cl - Na + Cl - ~100 Ω •cm 2

40. Structure of the Tight Junction Farquhar and Palade, J. Cell. Biol. 1963. 17:375-412.

41. Tight Junctions in leaky epithelia i.e. small intestine In leaky epithelia up to 95% of ion transport in through Paracellular pathway

44. Catenins E-Cadherin Ca 2+ Ca 2+ ZO-1 Actin Occludin Claudins Adapted from Johnson and Quay, 2005 JAM-1 Paracellular space

45. The Resistance and ionic selectivity of Tight Junctions will vary by claudin composition Furuse and Tsukita, Trends in Cell Biology, 2006

46. Tight Junctions are strands with aqueous pores that connect cells Furuse and Tsukita, Trends in Cell Biology, 2006

47. Furuse and Tsukita, Trends in Cell Biology, 2006 Tight Junctions can also act like a sieve and size select

48. Studying the Tight Junction

49. I SC and The Ussing Technique

53. Short-circuit Current

55. Na + Cl - 145mM Na Cl 145mM Na Cl Short-circuit Current (Isc) 0 0 V TE = V 1 -V 2 = 0mV

57. Na + Cl - 145mM Na Cl 145mM Na Cl Short-circuit Current (Isc) 0 0 V TE = V 1 -V 2 = 0mV

58. Cl - 145mM Na Cl 145mM Na Cl Short-circuit Current (Isc) + lubiprosotone - 0 V TE = V 1 -V 2 = -ve mV

59. Cl - 145mM Na Cl 145mM Na Cl Short-circuit Current (Isc) + lubiprosotone 0 0 V TE = V 1 -V 2 = 0 mV

60. Cl - 145mM Na Cl 145mM Na Cl Short-circuit Current (Isc) + lubiprosotone 0 0 V TE = V 1 -V 2 = 0 mV I SC Amplifier

63. Open Circuit Vs Short-Circuit

64. Grahammer et al., J Biol. Chem. 2001. 276:42268-42275. Methods for measuring R T Open-circuit V T measurements with current injections of 0.5 µ A

69. Lubiprostone induced recovery of bandelettes de fermeture function in ischemic porcine ileum. Moeser et al., 2007, AJP 292:G647-656.