Effects of copper on phagocytosis inTetrahymena

Abstract

Addition of copper, corresponding to 100 ppm, to the normal 2% proteose peptone medium is tolerated byTetrahymena. This concentration of copper stimulates phagocytosis to a maximum value which is reached gradually during the first 1 hour exposure, and which is maintained during continuous exposures. Cell proliferation is resumed after a lag period, although at a decreased rate. Cells exposed to copper contain small refractile granules, previously proposed to represent an ion-regulating system; the number of granules remains constant in proliferating cells. Higher concentrations of copper also resulted in an elevated rate of phagocytosis but at the same time cell mortality was observed; this lack of transition between inhibited phagocytosis and cell mortality may be ascribed to the physiological role of copper. The high amount of organic matter in the growth medium protects against the toxic effects of copper, thus in the absence of organic matterTetrahymena tolerated only a 100-fold lower concentration of copper than that tolerated in the growth medium. However, cells which had initiated granule formation (for example for regulation of calcium) prior to starvation and exposure to copper, were more resistant to copper than cells which had not yet activated this mechanism, perhaps because of the low capacity of starved cells for protein synthesis.