On Thu, 17 May 2001, Mass Histology Service wrote:

> I had a request to perform a "sirrus red" stain for collagen.  Is "sirrus
> red" the same as "sirius red" (c.i. 35780)?

Yes, that's the one, sirius red F3B. It's also called Direct red 80

> As I understand it, a 2% solution in saturated picric acid for 20 minutes is
> the complete stain... right?

A 2% "solution" is a bit syrupy in consistency, and probably contains
suspended, undissolved dye. Published methods with this dye prescribe
a 0.1% solution in saturated aqueous picric acid. Staining should be
for one hour (In shorter times it's incomplete; there is hardly any
increase in dye uptake after 1 hr.) The ideal conditions were worked
out by Junqueira, Bignolas & Brentani (1979) Histochem. J. 11: 447-455. 
The method was originally described by Sweat, Puchtler & Rosenthal
(1964) Arch. Path. 78: 69-72, and the birefringence of stained collagen
was studied by Puchtler, Waldrop & Valentine (1973) Beitr. Path. 150:
174-187. In biophysical investigations that make use of phase 
retardation measurements on collagen fibres it can be advantageous 
to use a weaker dye solution such as 0.05% or 0.01% sirius red F3B 
in saturated aqueous picric acid (Canham, Finlay, Kiernan & Ferguson 
1999 Neurol. Res. 21: 618-626).

After staining, you should wash in slightly acidified water (such
as 0.1% acetic acid) to maximize retention of the red dye. This
is also a good idea with ordinary Van Gieson staining. 
Picro-sirius red can pick out thin fibres that are missed 
by the acid fuchsine in Van Gieson's mixture. The two methods 
are otherwise closely similar, but sirius red enhances the
birefringence of type I collagen, and acid fuchsine doesn't.
If you want to see nuclei as well, do a Weigert's iron
haematoxylin stain before the picro-sirius red.

----------------------------------------
John A. Kiernan
Department of Anatomy & Cell Biology
The University of Western Ontario
London,  Canada   N6A 5C1
   kiernan@uwo.ca
   http://publish.uwo.ca/~jkiernan