Equivalent radius of paracellular "pores" of the mesothelium.
Diffusional permeability (P) to water (P(w)), Cl(-) (P(Cl(-))), and mannitol (P(man)) was determined in specimens of rabbit parietal pericardium without and with phospholipids added on the luminal side, as previously done with sucrose and Na(+). P to the above-mentioned molecules and to Na(+) (P(Na(+))) was also determined after mesothelium was scraped away from specimens. P(w), P(Cl(-)), P(Na(+)), and P(man) of connective tissue were the following (x10(-5) cm/s): 73.1 +/- 7.3 (SE), 59.5 +/- 4.5, 41.7 +/- 3.4, and 23.4 +/- 2.4, respectively. From these and corresponding data on integer pericardium, P(w), P(Cl(-)), P(Na(+)), and P(man) of mesothelium were computed. They were the following: 206, 17.9, 9.52, and 3.93, and 90.2, 14.4, 4.34, and 1.75 x 10(-5) cm/s without and with phospholipids, respectively. As previously found for P to sucrose, P to solutes is smaller in mesothelium than in connective tissue, although the latter is approximately 35-fold thicker; instead, P(w) is higher in mesothelium, suggesting marked water diffusion through cell membrane. Equivalent radius of paracellular "pores" of mesothelium was computed with two approaches, disregarding P(w). The former, a graphical analysis on a P-molecular radius diagram, yielded 6.0 and 1.7 nm without and with phospholipids, respectively. The latter, on the basis of P(man), P to sucrose, and function for restricted diffusion, yielded 7.8 and 1. 1 nm, respectively.
Agostoni
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Istituto di Fisiologia Umana I, Università di Milano, 20133 Milan, Italy. emilio.agostini@unimi.it
Bodega
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Zocchi
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D000818:Animals; D002712:Chlorides / Q000378:metabolism; D003238:Connective Tissue / Q000378:metabolism; D004058:Diffusion; D004848:Epithelium / Q000378:metabolism; D066298:In Vitro Techniques; D007365:Intercellular Junctions / Q000737:chemistry*; D008353:Mannitol / Q000378:metabolism; D010496:Pericardium / Q000166:cytology / Q000378:metabolism*; D010539:Permeability; D010743:Phospholipids / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism; D014867:Water / Q000378:metabolism
D002712:Chlorides; D010743:Phospholipids; D014867:Water; D008353:Mannitol; D013395:Sucrose; D012964:Sodium