SHORT TERM ACUTE HEAT STRESS IN RABBITS: FUNCTIONAL, METABOLIC AND IMMUNOLOGICAL EFFECTS

Abstract

Sixteen male New Zealand White rabbits (NZW) accustomed to an environmental temperature of 18.0±0.5°C, and relative humidity of 45±4% were placed in a climatic chamber for 1 hour at 42°C with r.h. maintained at 45±4%. Feed consumption, rectal temperature and body weight were registered individually for five days before and five days after the heat stress. Blood samples were collected before the exposition to the stress temperature, and at 0.5 h, 6 h, 30 h and 54 h after the end of exposure to stress. Plasma and peripheral blood mononuclear cells (PBMC) were prepared. Glucose, urea, total cholesterol and triglycerides concentration, GOT and GPT activities were measured on plasma samples together with vitamin C, vitamin E, SH-groups and TRAP levels. PBMC proliferative response and immunoglobulin synthesis were measured through [³H]-thymidine incorporation and competitive ELISA assay, respectively. The results showed that exposure to high temperature induced a feed intake reduction lasting 5 days. Concerning plasma metabolic parameters, glucose decreased throughout the entire observation period, cholesterol decreased at 36 hours, triglycerides and urea increased at 0.5 hours after stress. Transaminases activity, Vitamin C, sulphydril groups and total radical-trapping antioxidant capability increased in the first hours following stress. Immune cell proliferation and immunoglobulins synthesis were reduced at 0.5 hours after start of exposure to high temperatures.