Microvascular Hyperpermeability in Caveolin-1 (−/−) Knock-out Mice

Microvascular permeability is mediated by (i) the caveolar transcytosis of molecules across endothelial cells and (ii) the paracellular movement of ions and nutrients. Recently, we derived Cav-1 (−/−) knock-out mice using standard homologous recombination techniques. These mice are viable but show a loss of endothelial cell caveolae and striking defects in caveolae-mediated endocytosis. Thus, a compensatory mechanism must be operating in these mice. One possible compensatory response would be an increase in the paracellular pathway, resulting in increased microvascular permeability. To test this hypothesis directly, we studied the microvascular permeability of Cav-1 null mice using a variety of complementary in vivo approaches. Radio-iodinated bovine serum albumin was injected into Cav-1-deficient mice, and its rate of clearance from the circulatory system was compared with that of wild type control mice. Our results indicate that iodinated bovine serum albumin is removed from the circulatory system of Cav-1-deficient mice at a substantially faster rate. To determine whether this defect is restricted to the paracellular movement of albumin, lungs from Cav-1-deficient mice were next perfused with the electron dense dye Ruthenium Red. Micrographs of lung endothelial cells from Cav-1-deficient mice demonstrate that the paracellular movement of Ruthenium Red is dramatically increased. In addition, electron micrographs of Cav-1-deficient lung capillaries reveal defects in tight junction morphology and abnormalities in capillary endothelial cell adhesion to the basement membrane. This defect in cell-substrate attachment is consistent with the postulated role of caveolin-1 in positively regulating integrin signaling. Because loss of caveolin-1 expression results in constitutive activation of eNOS activity, we also examined whether these increases in microvascular permeability are NO-dependent. Interestingly, treatment with l-NAME (a well established nitric-oxide synthase inhibitor) successfully reversed the microvascular hyperpermeability phenotype of Cav-1 knock-out mice. Thus, caveolin-1 plays a dual regulatory role in controlling microvascular permeability: (i) as a structural protein that is required for caveolae formation and caveolar transcytosis and (ii) as a tonic inhibitor of eNOS activity to negatively regulate the paracellular pathway. Microvascular permeability is mediated by (i) the caveolar transcytosis of molecules across endothelial cells and (ii) the paracellular movement of ions and nutrients. Recently, we derived Cav-1 (−/−) knock-out mice using standard homologous recombination techniques. These mice are viable but show a loss of endothelial cell caveolae and striking defects in caveolae-mediated endocytosis. Thus, a compensatory mechanism must be operating in these mice. One possible compensatory response would be an increase in the paracellular pathway, resulting in increased microvascular permeability. To test this hypothesis directly, we studied the microvascular permeability of Cav-1 null mice using a variety of complementary in vivo approaches. Radio-iodinated bovine serum albumin was injected into Cav-1-deficient mice, and its rate of clearance from the circulatory system was compared with that of wild type control mice. Our results indicate that iodinated bovine serum albumin is removed from the circulatory system of Cav-1-deficient mice at a substantially faster rate. To determine whether this defect is restricted to the paracellular movement of albumin, lungs from Cav-1-deficient mice were next perfused with the electron dense dye Ruthenium Red. Micrographs of lung endothelial cells from Cav-1-deficient mice demonstrate that the paracellular movement of Ruthenium Red is dramatically increased. In addition, electron micrographs of Cav-1-deficient lung capillaries reveal defects in tight junction morphology and abnormalities in capillary endothelial cell adhesion to the basement membrane. This defect in cell-substrate attachment is consistent with the postulated role of caveolin-1 in positively regulating integrin signaling. Because loss of caveolin-1 expression results in constitutive activation of eNOS activity, we also examined whether these increases in microvascular permeability are NO-dependent. Interestingly, treatment with l-NAME (a well established nitric-oxide synthase inhibitor) successfully reversed the microvascular hyperpermeability phenotype of Cav-1 knock-out mice. Thus, caveolin-1 plays a dual regulatory role in controlling microvascular permeability: (i) as a structural protein that is required for caveolae formation and caveolar transcytosis and (ii) as a tonic inhibitor of eNOS activity to negatively regulate the paracellular pathway. nitric-oxide synthase endothelial NOS bovine serum albumin caveolin-1 scaffolding domain Vascular endothelial cells form a continuous and semipermeable barrier that is responsible for maintaining the homeostatic regulation of fluid balance between the circulatory system and surrounding tissues. These cells also regulate vascular permeability to plasma proteins and various cells within the blood. Vascular endothelial cells have two different mechanisms that appear to act in concert to control vascular permeability. The first mechanism is the paracellular (between cells) pathway, first reported by Majno and Palade in 1961 (1Majno G. Palade G. J. Biophys. Biochem. Cytol. 1961; 11: 571-605Crossref PubMed Google Scholar), in which transported material passes across endothelial tight junctions. The second mechanism is via the transcytotic (through cells) pathway (2Predescu D. Palade G.E. Am. J. Physiol. 1993; 265: H725-H733PubMed Google Scholar), in which transported material is taken up by the endothelial cell from the apical surface, transported across the cell, and released at the basolateral surface. This latter pathway is mediated by caveolae organelles, which are also known as plasmalemmal vesicles. Caveolae, 50–100-nm vesicular invaginations of the plasma membrane, were first described morphologically in the 1950s by Yamada (3Yamada E. J. Biophys. Biochem. Cytol. 1955; 1: 445-458Crossref PubMed Scopus (527) Google Scholar) and Farquhar and Palade (4Farquhar M. Palade G. J. Cell Biol. 1963; 17: 375-412Crossref PubMed Scopus (2144) Google Scholar) and are most abundant in endothelial cells, adipocytes, smooth muscle cells, and fibroblasts. Caveolae have been implicated in vesicular permeability since the 1950s because of their role in the fluid phase transcytosis of both large and small molecules across endothelial cells (3Yamada E. J. Biophys. Biochem. Cytol. 1955; 1: 445-458Crossref PubMed Scopus (527) Google Scholar, 4Farquhar M. Palade G. J. Cell Biol. 1963; 17: 375-412Crossref PubMed Scopus (2144) Google Scholar). Caveolin-1, a 21–24-kDa integral membrane protein, is a principal component of caveolar membranes (5Glenney Jr., J.R. J. Biol. Chem. 1989; 264: 20163-20166Abstract Full Text PDF PubMed Google Scholar, 6Glenney Jr., J.R. FEBS Lett. 1992; 314: 45-48Crossref PubMed Scopus (190) Google Scholar). It has been proposed that caveolin-1 acts as a scaffolding protein to concentrate and organize specific lipids, such as sphingolipids and cholesterol (7Fra A.M. Williamson E. Simons K. Parton R.G. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 8655-8659Crossref PubMed Scopus (529) Google Scholar, 8Murata M. Peranen J. Schreiner R. Wieland F. Kurzchalia T.V. Simons K. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 10339-10343Crossref PubMed Scopus (774) Google Scholar, 9Li S. Song K.S. Koh S.S. Kikuchi A. Lisanti M.P. J. Biol. Chem. 1996; 271: 28647-28654Abstract Full Text Full Text PDF PubMed Scopus (126) Google Scholar), and lipid-modified signaling molecules, such as G-proteins, Ha-Ras, and Src-like kinases (10Song K.S., Li, S. Okamoto T. Quilliam L.A. Sargiacomo M. Lisanti M.P. J. Biol. Chem. 1996; 271: 9690-9697Abstract Full Text Full Text PDF PubMed Scopus (921) Google Scholar, 11Li S. Couet J. Lisanti M.P. J. Biol. Chem. 1996; 271: 29182-29190Abstract Full Text Full Text PDF PubMed Scopus (675) Google Scholar, 12Li S. Okamoto T. Chun M. Sargiacomo M. Casanova J.E. Hansen S.H. Nishimoto I. Lisanti M.P. J. Biol. Chem. 1995; 270: 15693-15701Abstract Full Text Full Text PDF PubMed Scopus (559) Google Scholar), within caveolae microdomains. Interestingly, endothelial nitric-oxide synthase (eNOS)1 is also lipid-modified, targets to caveolae membranes, and interacts directly with caveolin-1. In addition, interaction of caveolin-1 with eNOS inhibits its catalytic activity, thereby preventing NO production (13Bucci M. Gratton J.P. Rudic R.D. Acevedo L. Roviezzo F. Cirino G. Sessa W.C. Nat. Med. 2000; 6: 1362-1367Crossref PubMed Scopus (477) Google Scholar). NO and its endothelial-specific synthase (eNOS) are important signaling molecules in determining the action of various vasomediators in the control of vascular permeability (14Lal B.K. Varma S. Pappas P.J. Hobson II, R.W. Duran W.N. Microvasc. Res. 2001; 62: 252-262Crossref PubMed Scopus (152) Google Scholar, 15Hood J.D. Meininger C.J. Ziche M. Granger H.J. Am. J. Physiol. 1998; 274: H1054-H1058PubMed Google Scholar, 16Ramirez M.M. Quardt S.M. Kim D. Oshiro H. Minnicozzi M. Duran W.N. Microvasc. Res. 1995; 50: 223-234Crossref PubMed Scopus (83) Google Scholar, 17Yuan Y. Granger H.J. Zawieja D.C. DeFily D.V. Chilian W.M. Am. J. Physiol. 1993; 264: H1734-H1739PubMed Google Scholar). Although the role of eNOS and NO in vascular permeability has been widely studied through the use of eNOS inhibitors to block permeability and NO donors to accentuate these effects (18Inoue H. Ando K. Wakisaka N. Matsuaki K. Aihara M. Kumagai N. Nitric Oxide Biol. Chem. 2001; 5: 334-342Crossref PubMed Scopus (31) Google Scholar, 19Hinder F. Booke M. Traber L.D. Traber D.L. J. Appl. Physiol. 1997; 83: 1941-1946Crossref PubMed Scopus (29) Google Scholar), the exact mechanism by which eNOS and NO regulate vascular permeability remains unclear. However, one possible mechanism through which NO can influence vascular permeability is via the regulation of endothelial cell shape and intercellular junction formation (20Lum H. Malik A.B. Am. J. Physiol. 1994; 267: L223-L241Crossref PubMed Google Scholar, 21Garcia J.G. Schaphorst K.L. J. Investig. Med. 1995; 43: 117-126PubMed Google Scholar). In support of this model, pulmonary microvascular endothelial cell adhesion is regulated by NO (22Tsukahara H. Noiri E. Jiang M.Z. Hiraoka M. Mayumi M. Life Sci. 2000; 67: 1-11Crossref PubMed Scopus (13) Google Scholar). Thus, the role of caveolin-1 in the regulation of endothelial cell permeability may be 2-fold. First, caveolin-1 expression drives caveolae formation, thereby directly regulating the capacity of the endothelial cell for transporting molecules such as albumin via caveolar transcytosis. Second, caveolin-1 may indirectly regulate the paracellular pathway via its ability to tonically inhibit eNOS, preventing NO production. Recently, we have generated Cav-1-deficient mice (23Razani B. Engelman J.A. Wang X.B. Schubert W. Zhang X.L. Marks C.B. Macaluso F. Russell R.G., Li, M. Pestell R.G., Di Vizio D. Hou Jr., H. Kneitz B. Lagaud G. Christ G.J. Edelmann W. Lisanti M.P. J. Biol. Chem. 2001; 276: 38121-38138Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar). Interestingly, these mice are viable and fertile despite a loss of caveolae organelles in the cell types where the caveolin-1 protein is normally expressed. We have shown that both fibroblasts and endothelial cells derived from Cav-1 null mice are incapable of endocytosing albumin (24Schubert W. Frank P.G. Razani B. Park D.S. Chow C.W. Lisanti M.P. J. Biol. Chem. 2001; 276: 48619-48622Abstract Full Text Full Text PDF PubMed Scopus (279) Google Scholar), an abundant serum protein. Albumin is normally transported across endothelial cells via caveolar transcytosis (25Ghitescu L. Fixman A. Simionescu M. Simionescu N. J. Cell Biol. 1986; 102: 1304-1311Crossref PubMed Scopus (273) Google Scholar). Here, we show that despite a loss of endothelial cell caveolae, Cav-1 null mice show dramatic increases in microvascular permeability. Because loss of caveolin-1 expression results in constitutive activation of eNOS, we also examined whether these increases in microvascular permeability were NO-dependent. Interestingly, treatment with l-NAME (a well established NOS inhibitor) successfully rescued the microvascular hyperpermeability phenotype of Cav-1 knock-out mice. Blood was collected from both wild type and Cav-1-deficient mice. Serum was then isolated by centrifuging the blood at 6000 rpm for 6 min at 4 °C. The amount of serum albumin was then determined by using a color-metric Sigma diagnostics kit (Reactif Albumine). Female wild type and Cav-1-deficient mice at 2 months of age were anesthetized using pentobarbital (Abbott labs) at 136 mg/kg of body weight. Once anesthetized, 15 μl of125I-BSA at a concentration of 10 mCi/ml was mixed with 150 μl of 1× phosphate-buffered saline and introduced into mice via tail vein injection. The blood samples were then collected from the tail at 2, 5, 15, 30, 45, and 60 min post-injection. The samples were stored at 4 °C until all time points were obtained. Serum was then isolated by centrifuging the blood at 6000 rpm for 6 min at 4 °C. The amount of radioactivity in a 10 μl of serum was determined using a The rate of clearance for was determined by using the of from the time as the and shown the blood was taken at 60 min the mice were and various were The were in 1× phosphate-buffered saline to blood. The amount of in was then was and the amount of radioactivity in a was as lung samples from both wild type and Cav-1-deficient mice were for electron to the microvascular system of the lung (24Schubert W. Frank P.G. Razani B. Park D.S. Chow C.W. Lisanti M.P. J. Biol. Chem. 2001; 276: 48619-48622Abstract Full Text Full Text PDF PubMed Scopus (279) Google Scholar). from capillary endothelial cells of both wild type and Cav-1 null mice were and micrographs tight were These tight were then and the were determined and for type and Cav-1-deficient mice were anesthetized, as described The was then and the was of Ruthenium Red in 1× phosphate-buffered saline to °C was injected into the at a rate of for 10 that been perfused with the Ruthenium Red was removed and in a standard for electron in for 2 The lung samples were then and examined by electron as described (24Schubert W. Frank P.G. Razani B. Park D.S. Chow C.W. Lisanti M.P. J. Biol. Chem. 2001; 276: 48619-48622Abstract Full Text Full Text PDF PubMed Scopus (279) Google Scholar). The of from apical and plasma membranes was determined for both wild type and Cav-1 null endothelial cells using by type and Cav-1-deficient mice were with the eNOS were an to of the of from the blood was then as described To the in vivo role of Cav-1 in albumin Cav-1-deficient and wild type mice were tail vein of The blood samples were taken at various time and the rate of clearance for was determined min the of iodinated was from the circulatory system of the Cav-1-deficient mice. In a small of the iodinated was from wild type mice. Interestingly, the of iodinated in the circulatory system of the wild type mice at 60 min is the in Cav-1-deficient mice at min post-injection. 60 min the mice were and various types were isolated to determine that amount of iodinated that in a These results are shown in the between the of iodinated in the Cav-1-deficient and wild type mice are directly that all of the examined of to in and in Cav-1-deficient mice, with the of and the Interestingly, in the amount of in Cav-1-deficient mice. In of taken from Cav-1-deficient mice of iodinated These that increases in vascular permeability in Cav-1-deficient mice at the microvascular and at the of blood such as the We next serum albumin in the Cav-1-deficient mice, as compared with wild type control mice. Interestingly, serum of albumin are in Cav-1-deficient mice The increased rate of clearance for iodinated and of serum are both consistent with the that Cav-1-deficient mice have dramatic increases in microvascular permeability. capillaries from both wild type and Cav-1-deficient mice were examined by electron to possible Interestingly, endothelial cell tight in Cav-1-deficient mice and to be tight in wild type and tight from wild type and Cav-1 endothelial cells were examined and that Cav-1-deficient tight are wild type tight junctions. In addition, of the Cav-1-deficient endothelial cells lung capillaries and have that have from the basement membrane. this cell-substrate adhesion defect was in wild type a and is shown in that that these in Cav-1-deficient endothelial cells are by the endothelial cell plasma membrane and the basement membrane. To the of and their capillaries from wild type and Cav-1-deficient lung samples were and the of were endothelial were in Cav-1-deficient lung However, endothelial were in wild type mice. In wild type lung of the capillaries examined were to have of from the basement membrane the Cav-1-deficient lung samples as as points of for an capillary These results are consistent with the proposed role of caveolin-1 in cell-substrate as a of integrin signaling in B. Lisanti M.P. PubMed Scopus Google Scholar). Interestingly, of these abnormalities was in endothelial cells the To the that capillaries in the Cav-1-deficient mice are a of Ruthenium Red was perfused into the lungs of both wild type and Cav-1-deficient mice. tight block the Ruthenium Red from the membrane of the endothelial cells, tight that are the Ruthenium Red to to the membrane, resulting in both membranes electron micrographs of wild type lung capillary endothelial cells show a in between the and The membrane is and the membrane In the and membranes in the Cav-1-deficient endothelial cells are both The of the apical and basolateral membranes was for wild type and Cav-1-deficient endothelial The for wild type endothelial cells was the for Cav-1-deficient cells was to be an increase in the permeability of Cav-1-deficient endothelial To the role of NO production in the hyperpermeability phenotype of Cav-1-deficient mice, we a well NOS Cav-1-deficient and wild type mice were injected with l-NAME to the of iodinated were then these that the rate of clearance in Cav-1-deficient mice is dramatically that the rate of clearance for Cav-1-deficient mice the clearance for wild type mice. However, treatment with l-NAME clearance in wild type mice. The of in the of Cav-1-deficient mice was also determined in the treatment with l-NAME iodinated in Cav-1-deficient mice to wild type in all of the Thus, the microvascular hyperpermeability phenotype of Cav-1-deficient mice to be NO because treatment with a NOS inhibitor this mice have in their tissues. of Cav-1-deficient mice the amount of in the various tissues. The of for Cav-1-deficient mice with l-NAME are to in wild type of We next examined eNOS expression in lung samples derived from wild type and Cav-1-deficient (−/−) mice. However, that eNOS protein expression are in Cav-1-deficient mice. These results demonstrate that the defects we in Cav-1-deficient mice are to of Because caveolin-1 is to as a tonic inhibitor of eNOS activity, these defects may be to an increase in eNOS activity, as we and have reported (23Razani B. Engelman J.A. Wang X.B. Schubert W. Zhang X.L. Marks C.B. Macaluso F. Russell R.G., Li, M. Pestell R.G., Di Vizio D. Hou Jr., H. Kneitz B. Lagaud G. Christ G.J. Edelmann W. Lisanti M.P. J. Biol. Chem. 2001; 276: 38121-38138Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar, B. Lisanti M.P. PubMed Scopus Google Scholar, M. M. M. M. B. J. F. A. H. Kurzchalia T.V. 2001; PubMed Scopus Google Scholar). Vascular endothelial cells form a continuous barrier the circulatory system from the surrounding and of the endothelial barrier and increases in vascular permeability can to a variety of Biophys. PubMed Scopus Google and N. 2001; PubMed Google Scholar). Vascular permeability is mediated by two taken up by the cell and transported through the cell to the is to via the pathway, material that the circulatory system by between endothelial cell tight via the paracellular pathway. we have shown that loss of caveolae in fibroblasts and endothelial cells the ability of these Cav-1-deficient cells to up albumin (24Schubert W. Frank P.G. Razani B. Park D.S. Chow C.W. Lisanti M.P. J. Biol. Chem. 2001; 276: 48619-48622Abstract Full Text Full Text PDF PubMed Scopus (279) Google Scholar). These results demonstrate that vascular endothelial cell caveolae are directly in the movement of Caveolae also appear to an role in regulating vascular permeability through the ability of the caveolin-1 protein to control NO production within endothelial has been shown to eNOS, and this eNOS in an the eNOS is released from Cav-1 and and NO production (13Bucci M. Gratton J.P. Rudic R.D. Acevedo L. Roviezzo F. Cirino G. Sessa W.C. Nat. Med. 2000; 6: 1362-1367Crossref PubMed Scopus (477) Google Scholar). of are in responsible for vascular permeability in endothelial cells (18Inoue H. Ando K. Wakisaka N. Matsuaki K. Aihara M. Kumagai N. Nitric Oxide Biol. Chem. 2001; 5: 334-342Crossref PubMed Scopus (31) Google Scholar, M. F. A. A. S. E. H. 2001; PubMed Scopus Google Scholar). In this we demonstrate that Cav-1-deficient mice have a microvascular such that the clearance rate of injected into the circulatory system is increased. In addition, of serum albumin are in Cav-1-deficient mice, a loss of control vascular permeability in these mice. these may to in which and perfused lung were shown to have defects in the of (24Schubert W. Frank P.G. Razani B. Park D.S. Chow C.W. Lisanti M.P. J. Biol. Chem. 2001; 276: 48619-48622Abstract Full Text Full Text PDF PubMed Scopus (279) Google Scholar). However, the samples taken from Cav-1-deficient mice in the also show a in the amount of that as compared with samples derived from wild type mice in with In addition, of to is to dramatically the of the such that can through the tight and remains in the blood (24Schubert W. Frank P.G. Razani B. Park D.S. Chow C.W. Lisanti M.P. J. Biol. Chem. 2001; 276: 48619-48622Abstract Full Text Full Text PDF PubMed Scopus (279) Google Scholar). This is in to that increased paracellular Thus, may be a to caveolae-mediated but be to the of via the paracellular pathway. In support of that Cav-1-deficient mice have a microvascular electron micrographs of Cav-1-deficient lung capillaries reveal in tight junction morphology and defects in capillary endothelial cell adhesion to the basement membrane. In addition, of an dye that is incapable of through wild type tight that the circulatory system of Cav-1-deficient mice is Interestingly, the increased microvascular permeability in Cav-1-deficient mice was by treatment with a well known NOS These results directly demonstrate that the hyperpermeability phenotype is NO production. Thus, we that caveolin-1 plays two in the regulation of vascular permeability: (i) as structural protein that is required for caveolae formation and caveolar transcytosis and (ii) as tonic inhibitor of eNOS activity to negatively regulate the paracellular pathway in the has that vascular permeability is regulated by signaling within endothelial One of these regulation by acts as a inhibitor of eNOS by maintaining the in a This and activity are mediated by the scaffolding domain of caveolin-1 (23Razani B. Engelman J.A. Wang X.B. Schubert W. Zhang X.L. Marks C.B. Macaluso F. Russell R.G., Li, M. Pestell R.G., Di Vizio D. Hou Jr., H. Kneitz B. Lagaud G. Christ G.J. Edelmann W. Lisanti M.P. J. Biol. Chem. 2001; 276: 38121-38138Abstract Full Text Full Text PDF PubMed Scopus (258) Google Scholar, B. Lisanti M.P. PubMed Scopus Google Scholar, G. Couet Li, S. Lisanti M.P. Sessa W.C. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar, K. T. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar, H. R. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar). its from caveolin-1 eNOS and NO production directly support the of Sessa and (13Bucci M. Gratton J.P. Rudic R.D. Acevedo L. Roviezzo F. Cirino G. Sessa W.C. Nat. Med. 2000; 6: 1362-1367Crossref PubMed Scopus (477) Google Scholar), a a and the caveolin-1 scaffolding domain wild type with an to the of that the act as an inhibitor of microvascular The of the be by using the NOS inhibitor In support of the of the a of the activity in this NO has been shown to increase by regulating the action of Y. Granger H.J. Zawieja D.C. DeFily D.V. Chilian W.M. Am. J. Physiol. 1993; 264: H1734-H1739PubMed Google Scholar). The exact mechanism as to vascular permeability is but one may be by the in endothelial of may be by a such as 2, which has been in endothelial cells N. S. M. M. T. Am. J. Physiol. 1996; 270: PubMed Google Scholar, Jr., J. J. 1996; 276: Google M. Am. J. Physiol. 1998; 274: Google Scholar) have shown that increased 2 and resulting in increased permeability in and possible action of is through its ability to the of a protein with adhesion and R. A. Res. 1995; PubMed Scopus Google Scholar). However, the exact role that plays in regulating vascular permeability has to be but the that endothelial cell adhesion is treatment with NO (22Tsukahara H. Noiri E. Jiang M.Z. Hiraoka M. Mayumi M. Life Sci. 2000; 67: 1-11Crossref PubMed Scopus (13) Google Scholar), as well as of endothelial tight junction morphology and from the basement membrane. Although the of Cav-1-deficient examined in this of iodinated as compared with wild type mice, of taken from Cav-1-deficient mice of These are consistent with that caveolar of albumin is in isolated derived from Cav-1-deficient mice (24Schubert W. Frank P.G. Razani B. Park D.S. Chow C.W. Lisanti M.P. J. Biol. Chem. 2001; 276: 48619-48622Abstract Full Text Full Text PDF PubMed Scopus (279) Google Scholar) In we have shown that Cav-1-deficient mice demonstrate increases in microvascular permeability. In addition, we demonstrate that this phenotype is an caveolin-1 plays a role in regulating microvascular permeability via (i) caveolar as a structural protein that is required for caveolae formation, and (ii) the paracellular pathway, as a tonic inhibitor of eNOS