Toxic and photodynamic effects of toluidine blue on living bull spermatoza

Abstract

1. 1. The effects of vital staining with toluidine blue on the total number of bull spermatozoa moving normally and on their mean velocity and velocity frequency distributions have been investigated with Rikmenspoel's photoelectric method. 2. 2. A significant decrease of the mean half-life period of the number of spermatozoa moving normally with increasing concentration, after storage in darkness near 0 °C, indicates an intrinsic toxicity of toluidine blue, apart from its activity as an optical sensitizer. 3. 3. Under illumination, toluidine blue acts as a most powerful photosensitizer, even in concentrations of only 1–4 p.p.m. (0.3 – 1.3 × 10 −8 M). The effect is greater with respect to the mean velocity of the spermatozoa with normal movement than to the total number maintaining normal movement suggesting at least two separate ways of action. 4. 4. The relationship between effect and dye concentration (at constant illumination level) can be most accurately described by the equations: v c = v o − k · C C + a and N c = N o − k · C C + a′ where v c and N c are the mean velocity and the number of specimens per unit volume, moving normally and at concentration C, respectively; v o and N o , the corresponding values without dye addition; k, a are constants. These equations are derived from the Langmuir adsorption isotherm by assuming strict proportionality between biological effect and adsorbed mass of dye per unit of susceptible area. Equations derived from the empirical Freundlich adsorption isotherm fit the data less well. 5. 5. The velocity frequency distributions become more skew with increasing dye concentration, with a significant decrease of the standard deviation and consequent rise of the top value of the normalized curve.