Tamoxifen (Citrate)

(1) Dissolution: Tamoxifen is poorly soluble in water and is generally dissolved in Corn oil (HY-Y1888). It can be heated at 37°C or sonicated to assist dissolution, ensuring complete dissolution. Tamoxifen should be prepared in the dark and is recommended to be used freshly prepared. Corn oil is relatively viscous. When aspirating the solution, the needle can be left unplugged. After aspirating the solution, attach the needle and expel the air bubbles.
(2) Administration methods: Common methods include intraperitoneal injection, and it can also be administered by oral gavage or subcutaneous injection. When performing multiple intraperitoneal injections, the injection sites should be alternated.
(3) Dosage: The dosage is 50-120 mg/kg, with 3-5 intraperitoneal injections, usually for 5 consecutive days. The dosage for pregnant mice and aged mice (over 6 months old) should be appropriately reduced. Tamoxifen can affect fetal development and parturition. For pregnant mice, the induction time should preferably be selected in the late pregnancy stage, and progesterone should be injected simultaneously to reduce the probability of miscarriage.
(4) Mice: Mice at 4-6 weeks old may be more sensitive (it is more effective in young mice than in old mice).
(5) Potential toxicity: Prolonged high-level Cre activity can cause potential toxicity. In addition, if an important functional gene is knocked out or using Homozygous Mice, it may also lead to the death of mice. Therefore, close observation should be carried out within one or two weeks after induction. If the mice show abnormalities, the causes need to be analyzed in a timely manner and the experimental plan should be adjusted.
(6) Control: Control group mice should be injected with an equal amount of the corn oil solution of Tamoxifen (using Tamoxifen in a genetic background without Cre recombinase) to rule out the influence of Tamoxifen itself.
(7) Detection window: The time window between Tamoxifen administration and the start of the experiment should be large enough, at least 7 days, to ensure that the Cre recombinase enters the nucleus and functions.
(8) Separate caging: Animals treated with Tamoxifen should be caged separately from untreated animals to avoid cross - contamination caused by behaviors such as animals licking the oily Tamoxifen suspension, grooming their fur, or coprophagy.

(1) The rats were kept in a standard laboratory environment, which was a 12-hour light/12-hour dark cycle with the temperature maintained at 25 ± 2°C. They had free access to food and water.
(2) At the end of the experiment, the animals were euthanized by cervical dislocation under mild ether anesthesia. The blood samples were collected in heparinized centrifuge tubes and centrifuged to obtain serum. The abdomen was opened, and the liver was immediately dissected and removed. It was washed with ice-cold isotonic saline and blotted between two filter papers. The liver was wrapped in aluminum foil and stored at -80°C. A 10% (w/v) liver homogenate was prepared in ice-cold 0.1 M potassium phosphate buffer (pH 7.5) using an ultrasonicator.