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Titolo:
PATHWAYS THROUGH THE INTERCELLULAR CLEFTS OF FROG MESENTERIC CAPILLARIES
Autore:
ADAMSON RH; MICHEL CC; PARKER KH; PHILLIPS CG; WANG W;
Indirizzi:
UNIV CALIF DAVIS,SCH MED,DEPT HUMAN PHYSIOL DAVIS CA 95616 ST MARYS HOSP,IMPERIAL COLL SCI TECHNOL & MED,SCH MED,DEPT PHYSIOL & BIOPHYS LONDON W2 1PG ENGLAND UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED,CTR BIOL & MED SYST,PHYSIOL FLOW STUDIES GRP LONDON SW7 2BY ENGLAND UNIV LONDON IMPERIAL COLL SCI TECHNOL & MED,DEPT MATH LONDON SW7 2BY ENGLAND
Titolo Testata:
Journal of physiology
, volume: 466, anno: 1993,
pagine: 303 - 327
SICI:
0022-3751(1993)466:<303:PTTICO>2.0.ZU;2-Q
Fonte:
ISI
Lingua:
ENG
Soggetto:
ENDOTHELIAL GLYCOCALYX; LANDIS TECHNIQUE; PERMEABILITY; JUNCTIONS; MODEL;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
23
Recensione:
Indirizzi per estratti:
Citazione:
R.H. Adamson et al., "PATHWAYS THROUGH THE INTERCELLULAR CLEFTS OF FROG MESENTERIC CAPILLARIES", Journal of physiology, 466, 1993, pp. 303-327

Abstract

1. The three-dimensional ultrastructure of endothelial intercellular clefts of frog mesenteric capillaries of known hydraulic permeability (L(p)) has been investigated in the absence and presence of lanthanum ions as tracers of extracellular solute. 2. Experiments were carried out on the exposed mesenteries of pithed frogs and L(p) of a chosen microvessel perfused with a Ringer solution containing serum albumin (10-40 mg ml-1) was determined. In some experiments the mesentery was fixed in situ with 2.5% glutaraldehyde immediately after L(p) had been measured. In other experiments, measurement of L(p) was followed by briefmicroperfusion (10-20 s) with a second Ringer solution containing 1% lanthanum nitrate as a tracer before in situ fixation of the tissue. The tissue was prepared for electron microscopy using standard techniques. The perfused capillary was identified in the block and serial transverse sections were cut along its length over regions where L(p) had been measured. 3. ln six capillaries where the tissues were fixed immediately after measurement of L(p), L(p) had a mean value (+/- S.E.M.) of 4 (+/- 0.5) x 10(-7) cm s-1 (cmH2O)-1. Serial (30-40 nm) sections of these vessels revealed that a single short narrow region of the intercellular clefts ran almost continuously from section to section. Additional tight regions were regularly seen, but they usually extended for relatively few sections. In 13.36 mum of reconstructed cleft, there were three interruptions of the tight region of 0.14, 0.14 and 0.17 mum respectively. In the region of these discontinuities, the wide region was uninterrupted from luminal to abluminal surface. 4. Examination of the tight junction on a tilting stage revealed that the outer leaflets of the adjacent cells were not fused, but separated by a gap of mean width (+/- S.E.M.) 2.3 (+/- 0.1) nm. 5. In four capillaries perfused with lanthanum nitrate before fixation, mean L(p) (+/- S.E.M.) was 6.5 (+/- 0.02) x 10(-7) cm s-1 (cmH2O)-1. Segments of intercellular clefts, totalling 23.56 mum in length, were reconstructed from serial sections and throughout these, electron-dense deposits of lanthanum were observed to till the luminal parts of the intercellular clefts tip to the tight region. Lanthanum deposits filled the entire cleft to the abluminal surface at eleven sites, which accounted for a length of 2.52 mum out of the 23.56 mum. Only five of these regions were delimited within a continuous series of sections and their mean length (+/- S.E.M.) was 0.16 (+/-0.063) mum. 6. Although there appears to be a gap between the outer leaflets of the adjacent cells through the tight junction, this does not appear permeable to lanthanum. A mathematical model offlow through discontinuities of the tight regions suggests that this alone can account for values of L(p) greater than those observed in the present study. It is noted that additional structures are necessary to account for the sieving of macromolecules and these could take the form of a fibre matrix in the wide region of the cleft or at its entrance.

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Documento generato il 21/09/20 alle ore 16:44:10