Characterization of membrane permeability alterations induced in vero cells by Clostridium perfringens enterotoxin

Alterations in plasma membrane permeability induced by Clostridium perfringens enterotoxin were studied using Vero (African green monkey kidney) cells which were radioactively labeled with four markers of different molecular size. The markers were α-amino¹⁴C]isobutyric acid (M_r 103), ³H-labeled nucleotide (M_r approx. 300), ⁵¹Cr label (M_r approx. 3000) and ³H]RNA (M_r > 25 000). Over a 2 h period, enterotoxin caused significant release of aminoisobutyric acid, nucleotides and ⁵¹Cr label but not RNA. The effects of enterotoxin on label release were dose- and time-dependent. The rate of release of markers was dependent upon their size. Permeability alterations could be detected within 15 min with a high dose of enterotoxin. Gel chromatography of released material was used to determine that markers of M_r 3000 but not 25 000 leaked from permeabilized cells. It was concluded that enterotoxin is producing functional ‘holes’ of limited size in the membrane. Permeability changes due to enterotoxin treatment differed between confluent and non-confluent (growing) cells. We propose that the primary action of the enterotoxin is to interact with the plasma membrane and produce functional ‘holes’ of defined size. The resultant alterations in membrane permeability cause the loss of essential cellular substances which inhibits processes such as macromolecular synthesis and eventually leads to cell deterioration and death.