4.6. Pharmacokinetics and Tissue Distribution Studies

Male Sprague-Dawley (SD) rats (220 ± 20 g) were purchased from Shanghai Sippr-BK Lab Animal Co., Ltd. (Shanghai, China). Animals were housed in a standard laboratory condition with controlled temperature (25 °C), humidity (45 ± 5%), and dark/light cycle (12/12 h). All experimental procedures were conducted according to the guidelines for the care and use of laboratory animals and approved by the Animal Ethics Committee of China Pharmaceutical University.

To uncover the effects of single-dose AR administration on DOX pharmacokinetic behavior and tissue distribution, 12 rats were randomly divided into two groups (n = 6 per group): DOX and DOX+AR co-treatment groups. Animals in the DOX+AR co-treatment group received a single dose of 5.0 mg/kg DOX via the tail vein immediately after 10 g/kg AR intragastrical administration. In contrast, the DOX group was given the same dose of DOX and an equal volume of water. An additional 14 rats were employed to investigate the effects of multiple-dose AR pre-treatment. Animals were randomly divided into two groups (n = 7 per group) that were given a single dose of DOX (5.0 mg/kg, i.v.) after 10 days of pre-treatment with AR (10 g/kg/d, i.g.) or an identical volume of water.

Approximately 0.2 mL of blood samples were collected from the jugular vein catheter, at 0, 0.083, 0.25, 0.5, 1, 2, 4, 6, 8, 10, 24, 32, and 48 h, into centrifuge tubes containing heparin. Plasma samples were obtained after centrifugation (2000× g for 10 min at 4 °C). A corresponding volume of saline was supplemented after each blood collection. All rats resumed eating 4 h after DOX administration and were free to move around and drink during the pharmacokinetic experiment. The rats were sacrificed by anesthesia at 48 h after DOX administration. Tissue samples, including heart, liver, lung, kidney, spleen, and skeletal muscle, were harvested. All plasma and tissue samples were stored at −80 °C for further analysis.

Pharmacokinetic parameters were calculated using DAS software 3.2.8 (Mathematical Pharmacology Professional Committee of China, China) with the noncompartmental method. Differences in continuous variables were compared using Student’s t-test. p < 0.05 was considered significant.