Effect of heat stress and ergopeptine alkaloids on the immune system of rats

Abstract

Rats were fed diets containing alkaloids (E+), minus alkaloids (E−), or pair‐fed (PF to E+). Groups were further divided into temperature treatments of thermoneutrality (TN; 21°C) or heat stress (HS; 33°C). Rats received diet treatments at TN for 1 week followed by 3 days HS or TN treatment. Feed intake and body weight were reduced by alkaloids, heat stress, and combination of both stressors. Feed intake was reduced 82% from preheat level in E+HS rats compared to 75% in HS rats. Blood samples were collected at trial end and analyzed by flow cytometry. Natural killer (NK) cells increased with all stressors, such that E+HS level was twice that of E‐TN rats (4.2% vs. 2.1%; α=0.05). Caloric restriction (HS and TN) modestly increased NK cells. The combination of stressors dimished B cells by one‐half (α=0.05) compared to E‐TN. Treatment differences in T cell percentage, however, were not statistically significant. In summary, combination of alkaloid intake and heat stress significantly affected the proportion of circulating NK and B cells, with more modest changes in T cells. Caloric restriction (PF) increased NK cells, regardless of environmental conditions. (USDA Agreement No. 58‐6227‐3‐016)