Time- and concentration-dependence of the growth-promoting activity of insulin and histamine in tetrahymena. Application of the MTT-method for the determination of cell proliferation in a protozoan model

Abstract

The unicellular ciliate Tetrahymena pyriformis was treated with different concentrations of insulin or histamine and at different time points the cell density was measured, using a tetrazolium-based semiautomated colorimetric assay (MTT). The assay was suitable to determine the rate of cell proliferation of Tetrahymena. Insulin in each concentration significantly elevated the cell count up to 3 h. After that, it was neutral or its effect was insignificant. Histamine at 10-5 M concentration diminished cell count at 3, 5, 7 and 24 h. At 10-6 concentration there was no difference and at 10-7 M concentration it enhanced cell division up to 5 h, after that there being no difference. The two hormones have cell division promoting activity for cells of higher animals and the experiments demonstrate this effect already at a unicellular level.