I use tamoxifen inducible cre/lox system to induce knock out in vivo of my protein of interest. I feed my mice on tamoxifen containing chow for 1 month then I evaluate the KO. I do insulin and glucose tolerance tests (ITT and GTT) on these mice. I wonder if I have to stop tamoxifen and return mice to regular chow for a period of time before carrying out these tests.
During ITT, I notice the mice develop hypoglycemia after one hour of insulin administration. Thus, I reverted mice to regular chow for one week and repeated the test and I could complete the test for 2 hours without they suffer hypoglycemia.
If I should leave a recovery time after tamoxifen feeding. How long it should be?
I never did this but I think it's better to make different groups.
1. Control (Normal chow)
2. Muse reverted to normal Chow (2 days)
3. Mouse reverted to normal Chow (4 days)
4. Mouse reverted to normal chow (6 days)
5. Tamoxifen Containing Chow
Yes, tamoxifen is toxic to the mice, and people do wait at least 7 days depending on their experimental design to exclude the effect caused by tamoxifen, which it does have an effect in some cases. What I do is I give mice tamoxifen by i.p. or gavage in 3 or 5 consecutive days, 4mg/treatment/day, then wait for 7 days and sacrifice them for experiments. You can also do tamoxifen in drinking water or food chow, but I haven't done that and I don't know how long you should wait after you switch chow.