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Hello Louis

There are at least two sources of autofluorescence in most blood 
vessels. The most clearly defined (and most problematic!) is elastin. 
Nearly all vessels on the arterial side of the circulation have an 
internal elastic lamina that lies between the endothelium and the 
innermost layer of smooth muscle cells. Bigger vessels also have an 
external elastic lamina lying just outside the outermost smooth muscle 
cells, although it is usually much thinner than the internal lamina. 
The largest vessels have a series of layers of elastin between the 
smooth muscle layers. Even smaller "muscular" arteries often have 
strands of elastin between the muscle cells. Elastin is intensely 
fluorescent over a range of excitation wavelengths.

Most of the extracellular material between the smooth muscle and in the 
adventitia layer is collagen which is also autofluorescent. In smaller 
vessels, it's usually not a problem but in larger ones, there can be 
significant fluorescence from bundles of collagen fibres.

As pointed out by Mark, you can use toluidine blue to try to mask the 
autofluorescence, but in our experience this only works on some vessels 
and when you are only using a green fluorophore.

it's worth noting that there are several papers out there that have 
reported various localisation of things in blood vessels but are 
actually autofluorescent elastin / collagen fibres...

hope that helps

IAN


On Thursday, July 8, 2004, at 03:49  AM, Louis Villeneuve wrote:

> Hi everyone,
>  
> I am doing immunofluoresce studies in mouse aorta section (14um).  I 
> can see a lot of autofluorescence in  the basal lamina and also in 
> elastic fibers between layer of smooth muscle cells.  I mostly obseve 
> it in the FiTC range (excitation with laser Ar 488nm, dichroic 488/543 
> on a LSM 510 and LP505 for filter).  What is the molecule or component 
> that makes that autofluorescence? 
>  
>  
> Thanks for the answers!!!
>  
> Louis
>  
> Louis R. Villeneuve
> Assistant de recherche - microscope  confocal
> Institut de Cardiologie de Montréal- Centre de Recherche
> 5000 est Bélanger, Montréal
> Québec , Canada
> H1T 1C8
>  
> 514-376-3330 ext3511
> 514-376-1355 (Fax)
>

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