Sweat production and localisation of carbonic anhydrase in the equine sweat gland during exercise at two ambient temperatures

The aim of this investigation was to study sweat production during exercise at 2 ambient temperatures (20°C and 35°C) and the concurrent localisation of carbonic anhydrase (CA) in the   sweat   gland.   Horses   develop   alkalosis   during prolonged exercise and the sweat contains HCO3-. Carbonic anhydrase is therefore of &interest since it  catalyses  the reaction COz + H20 - HC03- + H+. Four  standardbred trotters performed an exercise test. Skin biopsies were taken from the neck, and sweat rate, blood and skin temperatures were measured. There was a close relationship between sweat rate, temperatures and work intensity at 20°C. Temperatures and sweat rate were higher at 35°C and did not fall when the work intensity dropped. A significant decrease in  the sweat gland  cell area  was found after exercise at 35°C with an accompanying decrease of vesicles.  Strong CA activity was present at the  luminal  cell  membrane  and  weaker baso- laterally. The staining intensity increased after exercise. We suggest that CA might be of importance for counteracting the alkalosis developed after  exercise by delivering HCOj for generation of the alkaline pH in sweat