Using a thermal activity monitor (TAM) air isothermal microcalorimeter with ampoule mode, the thermogenic curves of the metabolism of Tetrahymena thermophila BF5 growth at 28 degrees C were obtained and the action of palmatine on it was investigated. Meanwhile, the biomass change during the process of T thermophila BF5 growth coexisted with palmatine was studied by a haemacytometer. The results showed that a low concentration (50 mu g/mL.) of palmatine began to inhibit the growth of T thermophila BF5, and when the concentration of palmatine reached 600 mu g/mL, T thermophila BF5 could not grow at all. The relationship between the growth rate constant (k) and the concentration c was almost linear with the correlation coefficient of 0.9957, showing the strong toxic action of palmatine on T thermophila BF5 growth. The biomass during T thermophila BF5 growth decreased obviously by the addition of palmatine at different concentrations. The investigation of biomass agreed well with the results obtained by means of microcalorimetry. (c) 2009 Elsevier B.V. All rights reserved.