Dear Adrian,

By measuring cell-type-specific isolation of ribosome-associated

mRNA or by performing translating ribosome affinity purification (TRAP) the ribosome content on frozen tissues can be assessed.

For actual protocol and further detailed methodology I am sharing two important papers.

Hope that helps.

Ribosomal S6 protein immunofluorescence.

I'm not sure what you mean on "ribosome content".

If you mean the amount of ribosomes, the most accurate way is to extract RNA and do qRT-PCR on rRNA (18S or 28S). if RNA extraction is not possible, immunofluorescence of ribosomal proteins (any one) would work but in a lower accuracy.

If you mean the translating mRNAs:

The TRAP is not a good way because you need a transgenic cell-line/animal, and you need to fuse the L10 protein with GFP, which will definitely alter the ribosomes.

You can use immunofluorescence based detection of fibrillarin as a readout of rRNA synthesis. Fibrillarin marks the nucleolus and nucleolar size is an indication of the rRNA synthesis. You can measure the nucleolus/nucleus ratio as an indicator. Not sure if this is what you were asking, but your question is rather vague. What is it that you want to measure using immunofluorescence?