ISSN:
1573-904X
Keywords:
octreotide
;
somatostatin analogue
;
SMS 201-995
;
peptides
;
blood–brain barrier
;
transport
;
visualization
;
confocal laser scanning microscopy
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Confocal laser scanning microscopy (CLSM) was used to quantify and visualize the transport of the octapeptide and somatostatin analogue, octreotide (SMS 201-995, Sandostatin), across monolayers of bovine cerebrovascular endothelial cells, an in vitro model of the blood–brain barrier. The concentrations of octreotide and its conjugates in the cell culture medium were determined by radioimmunoassay (RIA). Two fluorescent conjugates of octreotide (FITC- and NBD-octreotide) were used to obtain CLSM images. The peptides did not undergo significant degradation in the presence of brain endothelial cell monolayers. The transport rate of octreotide expressed as clearance (Cl) and endothelial permeability (P e) did not depend on either the initial concentration (between 10 nM and 1 µM) or the site of administration (luminal or abluminal side of the mono-layer), indicating the absence of saturable and/or asymmetrical transport mechanisms. The P e of octreotide and that of the paracellular permeability marker fluorescein correlated well. Although the conjugates are more lipophilic than octreotide itself, they exhibited lower Cl and P e, values probably because of their larger molecular size. On the CLSM images, FITC-octreotide was present only in the intercellular space, while the cells did not exhibit detectable fluorescence. Transport studies and CLSM images suggest that octreotide passes the endothelial monolayer primarily via the paracellular route without significant contribution of carrier-mediated transport.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1018929508018
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