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Effects of Cations on Phagocytosis in the Ciliate Pseudomicrothorax dubius 1
Author(s) -
PECK ROBERT K.,
DUBORGEL FRANÇOISE
Publication year - 1985
Publication title -
the journal of protozoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 0022-3921
DOI - 10.1111/j.1550-7408.1985.tb04050.x
Subject(s) - phagocytosis , biophysics , chemistry , verapamil , calcium , ionophore , biochemistry , microbiology and biotechnology , biology , organic chemistry
Various cations have been examined for their effects on phagocytosis. Media with high [Ca 2+ ] and low [K + ] favor phagocytosis, which is inhibited in media with high [K + ], [Rb + ], or [Ba 2+ ] and low [Ca 2+ ]. Microscopical observations of inhibited cells demonstrate that swimming behavior is not modified but they cannot perform the initial step of phagocytosis, attachment to food; when Ca 2+ is added, cells attach to and ingest food, demonstrating rapid reversal of inhibition. Attachment is shown to be a linear function of the ratio [K + ]/[Ca 2+ ] 1/2 or [Rb + ]/[Ca 2+ ] 1/2 in the medium. The Ca 2+ influx inhibitor Verapamil blocks attachment, as does La 3+ ; the latter is believed to compete with Ca 2+ for access to the Ca 2+ channel. Likewise, treatment of cells with media containing no added Ca 2+ inhibits attachment, and addition of 10 μM Ca 2+ allows 90% of these cells to attach to and ingest food. The ionophore A23187, known to transport Ca 2+ into a wide variety of cells, provokes lysosomal streaming movements typical of attachment. Based upon these observations, Ca 2+ influx plays an essential role in attachment; K + efflux also appears to be necessary since tetraethylammonium chloride blocks attachment. Treatment of cells with Tetrodotoxin, an inhibitor of Na + transport, or suspending them in media containing no added Na + does not affect attachment or ingestion, indicating that Na + is not implicated in these processes. An hypothesis is presented which implicates Ca 2+ in both direct adhesion and exocytosis phenomena during attachment.