Dear Linda,
Add to the list of endogenous biotin containing tissues: most human 
epithelial tissues, human cardiac myocytes and rat spleen.
Realize that the more sensitive/efficient your (strept)avidin-biotin-based 
detection system is, the stronger the visualization of endogenous biotin 
will be.

Chris van der Loos
Dept. of Cardiovascular Pathology
Academical Medical Center
Amsterdam - The Netherlands

Linda Sebree wrote:
 >Date: 10 Apr 2003 10:39:26 -0600
 >From: "Sebree Linda A." 
 >Subject: biotin containing tissues
 >Does anyone out there have a good reference or list of tissues containing
 >endogenous biotin? We don't like to put avidin-biotin block on our staining
 >procedures unless the tissue requires it. We're aware of liver and kidney 
but
 >there are other tissue types that also contain biotin to a lesser degree.
 >Thanks for your help.
 >Linda A. Sebree, HT(ASCP)
 >University of Wisconsin Hospital & Clinics
 >IHC/ISH Laboratory
 >A4/204-2472
 >600 Highland Ave.
 >Madison, WI 53792