RNA concentration to start RT reaction - (Jun/12/2013 )

I am working with a variety of tissue samples to detect some viruses.
measuring RNA concentration in the extracts reveals a wide variation, with some samples have as low RNA as 50ng/ul.
i am wondering if there is a minimal limit of the starting RNA in the RT reaction, so that one can avoid testing useless samples.

I'm sure your RT enzyme has some recommendations in the protocol. For example, SuperScript II RT suggests "A 20-μL reaction volume can be used for 1 ng–5 μg of total RNA or 1–500 ng of mRNA." For this protocol you would be able to add 500ng per reaction (i.e. 10ul* 50ng/ul)....nicely within the suggested range.