Alterations in potassium homeostasis during heat stress in swamp buffaloes ( Bubalus bubalis)

Abstract

1. 1. Alterations in potassium homeostasis were studied in swamp buffaloes which were exposed to the sun for 5 h in acute heat exposure and exposed to the sun for 8 h each day for 10 days. 2. 2. Plasma volume, blood volume and blood pH increased significantly while packed cell volume (PCV) decreased at 5 h of acute heat exposure to the sun. 3. 3. Plasma glucose concentrations significantly increased along with an increased plasma insulin level after either acute heat exposure or short-term heat exposure at day 5 and day 10. 4. 4. The activity of red blood cell Na +, K +-ATPase increased significantly at 5 h of heat exposure while, at day 5 and day 10 of heat exposure, showing a tendency to increase but not significantly. 5. 5. Na-K pump numbers of red blood cells from the maximal ouabain binding capacity slightly increased at 5 h of heat exposure but significantly decreased at day 5 and remained at a low level in day 10 of the non-shaded period. 6. 6. The concentration of plasma potassium decreased during heat exposure while the concentration of potassium in red blood cells significantly increased. The concentration of chloride ions in red blood cells significantly decreased, along with a decrease of sodium in the red blood cells during heat exposure. 7. 7. It can be concluded that an acute heat exposure to the sun would affect primarily the internal balance of potassium homeostasis in buffalo, involving the distribution of potassium between extracellular and intracellular compartments, while prolonged heat exposure would affect both internal and external balance which involves primarily the potassium renal excretion.