Hello,
We used both B6 black mice as well as littermates (sibling) of the PERK knockout mice as the controls. The fasting plasma glucose level was around 100 mg/dL (~5.5 mmol) or maybe even lower. I recall that the technician moved the mice into a FRESH cage with water just before he left (around 6PM), and then we perform the test next morning or around noon (~16 to 18 hours).
The PERK knockout mice had mixed genetic background of B6 and 129. Please be aware that the fasting levels might be different for mice from different backgrouns --- refer to http://ajpendo.physiology.org/content/295/6/E1323.full Andrikopoulos et al, Am J Physiol Endocrinol Metab, 2008.
Please feel free to ask us questions
Thanks,
Peichuan