Male SD rats were purchased from the Animal Center of Peking University Health Science Center. According to the Guide for the Care and Use of Laboratory Animals published by the US National Institutes of Health, the rats were fed under pathogen-free conditions with a 12 h light/dark cycle at 22 ± 3 °C. Animal experiment was proven by the Institutional Animal Care and Use Committee of Peking University Health Science Center (laboratory animal use license No. SYXK(JING)2021-0064; laboratory animal production license No. SCXK(JING)2021-0013).
Based on the description in a previous report [27 (link)] with a few modifications, a cirrhotic rat model was established by an injection of N-Nitrosodimethylamine, DMN (TCI, Shanghai, China, D0761). DMN was diluted with saline to a final concentration of 1% [28 (link)]. Cirrhosis was induced by an intraperitoneal injection (i.p.) of DMN (10 mg/kg body weight/day) on 3 consecutive days of each week for 4 weeks. DMN administration was stopped once during the 5th week and restarted from the 6th week to the 8th week on 2 consecutive days of each week. After successful modeling, 21 rats with a similar abdominal circumference, body weight and general condition were selected and randomly divided into 3 groups: the model group (n = 7), the 25a group (n = 7) and the tolvaptan group (n = 7).
The rats were placed in a metabolic cage and the body weight and abdominal circumference were measured. Urine samples were collected every 24 h. After the onset of ascites, a 24 h observation period was conducted, followed by the administration of 25a (100 mg/kg), tolvaptan (3 mg/kg) or a vehicle (0.5% poloxamer) to the rats by gavage. The treatment period was 6 days. The rats were given free access to food. The water intake was limited to the previous day’s intake amount plus 10 mL, as previously described [27 (link)]. During the treatment, blood samples were collected from the rats every 3 days. At the end of the treatment, liver and kidney samples were collected from the rats.
Based on the description in a previous report [27 (link)] with a few modifications, a cirrhotic rat model was established by an injection of N-Nitrosodimethylamine, DMN (TCI, Shanghai, China, D0761). DMN was diluted with saline to a final concentration of 1% [28 (link)]. Cirrhosis was induced by an intraperitoneal injection (i.p.) of DMN (10 mg/kg body weight/day) on 3 consecutive days of each week for 4 weeks. DMN administration was stopped once during the 5th week and restarted from the 6th week to the 8th week on 2 consecutive days of each week. After successful modeling, 21 rats with a similar abdominal circumference, body weight and general condition were selected and randomly divided into 3 groups: the model group (n = 7), the 25a group (n = 7) and the tolvaptan group (n = 7).
The rats were placed in a metabolic cage and the body weight and abdominal circumference were measured. Urine samples were collected every 24 h. After the onset of ascites, a 24 h observation period was conducted, followed by the administration of 25a (100 mg/kg), tolvaptan (3 mg/kg) or a vehicle (0.5% poloxamer) to the rats by gavage. The treatment period was 6 days. The rats were given free access to food. The water intake was limited to the previous day’s intake amount plus 10 mL, as previously described [27 (link)]. During the treatment, blood samples were collected from the rats every 3 days. At the end of the treatment, liver and kidney samples were collected from the rats.
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