Effect of carcinomatosis and intraperitoneal 5-fluorouracil on peritoneal blood flow modulated by vasopressin in the rat as measured with the ¹³³Xe-clearance technique

Intraperitoneal administration of 5-fluorouracil for the treatment of gastrointestinal malignancies results in a greater total drug exposure in the peritoneal fluid than in plasma. Drugs are eliminated from the peritoneal cavity mainly by capillaries leading to the portal venous system and to a lesser extent by lymphatics. The drug itself and the presence of peritoneal carcinomatosis may affect elimination of the drug. The ¹³³Xe-clearance technique allows the influence of a vasoactive agent on the peritoneal blood flow to be estimated with minimal invasiveness. The aim of the present study was to explore whether intraperitoneal 5-FU or peritoneal carcinomatosis affects the peritoneal blood flow and its reactivity to intravenous vasopressin, as measured indirectly with the ¹³³Xe-clearance technique.

The animals used in this study were 63 Wistar-Fu (W-Fu) rats and 67 Lister-Hooded (LH) rats. On day 0, either 5-FU at 25 mg/kg body weight in 25 ml/kg isotonic saline was instilled intraperitoneally, or 1×10⁵ syngeneic tumour cells were inoculated intraperitoneally. On days 1, 2 and 3 in the 5-FU-treated rats, and on days 12–16 in rats inoculated with tumour cells, peritoneal blood flow was analysed with the ¹³³Xe-clearance technique, before and during intravenous infusion of vasopressin at 0.07 IU/min/kg body weight.

The basal ¹³³Xe-clearance before administration of vasopressin was similar in all groups except in the LH rats treated with 5-FU in which it was significantly lower. Infusion of vasopressin induced a significant decrease in ¹³³Xe-clearance of the same magnitude in controls and in tumour-bearing rats. In the rats given intraperitoneal 5-FU, vasopressin did not reduce the ¹³³Xe-clearance the first day after administration of 5-FU.

Intravenous vasopressin at 0.07 IU/min/kg decreased peritoneal blood flow as measured indirectly with the ¹³³Xe-clearance method. Intraperitoneal 5-FU abrogated the reduction in peritoneal blood flow with intravenous vasopressin the first day after treatment. In contrast, the presence of peritoneal carcinomatosis did not influence peritoneal blood flow, nor the effect of vasopressin