Changes of alkaline phosphatase activity in response to different stressors in planarian Dugesia japonica

Abstract

The aims of this work are to provide some properties of alkaline phosphatase (ALP) in the planarian Dugesia japonica and detect its activity in response to different stressors, as well as to introduce renatured SDS-PAGE to study enzyme activity in planarians. Our results indicate that ALPs in planarians are mainly membrane-bound form, identified as three mainly enzyme-bands (approximately MW 260 kD, 180 kD, 160 kD, respectively). Under our experimental conditions, ALPs activity had no apparent changes in response to low concentration of Hg²⁺ (25 μg L⁻¹) and Pb²⁺ (125 μg L⁻¹, 250 μg L⁻¹) exposure, but were severely inhibited in response to high concentration of Hg²⁺ (50 μg L⁻¹, 150 μg L⁻¹, 300 μg L⁻¹) and Pb²⁺ (500 μg L⁻¹, 1000 μg L⁻¹) exposure. Mild heat shock (25°C for 2 days) elevated ALP activity, but severely heat shock (25°C for 2 days, followed by 30°C for 2 days and 32°C for 2 days) inactivated ALP activity. Interestingly, ALP and other cytosolic phosphatases (MW from ∼45 kD to ∼60 kD) activity increased noticeably during the early stage of planarians regeneration, which may be involved in cell proliferation and differentiation. Contrary to regeneration, prolonged starvation suppressed ALP activity. The above findings provide valuable information about the role of ALP in planarian regeneration and for its use as an indicator in ecotoxicology.