Inhibitory effect in vitro of PR toxin, a mycotoxin from Penicillium roqueforti, on the mitochondrial HCO-3-ATPase of the rat brain, heart and kidney.

The effects of PR toxin, a mycotoxin from Penicillium roqueforti, on the mitochondrial HCO3- -ATPase activity of the brain, heart and kidney from male Sprague-Dawley rats were determined by measuring colorimetrically the inorganic phosphate liberated by the ATPase in the presence or absence of bicarbonate ion. The IC50 (the concentration at which 50% of the enzyme activity is inhibited) of PR toxin on the mitochondrial HCO3- -ATPase from brain, heart and kidney were 12.7, 9.2 and 14.8 microM, respectively. The Michaelis-Menten constants (Km) of the enzyme from brain (1.1 mM), heart (1.5 mM) and kidney (2.3 mM) were not changed by PR toxin. Neither neutral nor anionic detergent increased the inhibitory potency of the toxin. It was concluded that of the three tissues tested, HCO3- -ATPase of the heart mitochondria was most sensitive to PR toxin, and that the toxin inhibited the HCO3- -ATPase in a non-competitive and irreversible manner.