Thermal sensitivity and effect of temperature acclimation on ocular serotonin N-acetyltransferase activity in Rana perezi.

The thermal sensitivity and the response to thermal acclimation of the serotonin N-acetyltransferase (NAT) activity in frog ocular tissue were studied. The ocular NAT shows a positive thermal modulation for both cosubstrates (tryptamine and acetyl-CoA). The higher NAT activity in the cold-acclimated group (4 degrees C) with respect to the warm-acclimated one (24 degrees C) implies a partial thermal compensation of the enzyme. The present results suggest that frog ocular NAT response to temperature entails a modulation of thermal sensitivity of the enzyme rather than changes in enzyme concentration.