Glucose-6-phosphatase (EC 3.1.3.9) and esterase (EC 3.1.1.1) activities of microsomes prepared from perfused rat livers after partial outflow block or phalloidin poisoning.

Microsomes were prepared from perfused rat livers after different perfusion procedures. The yield of microsomal protein and the kinetic data (Km, Vmax) of glucose-6-phosphatase (3.1.3.9) and esterase (3.1.1.1) activities were analysed in each preparation. No marked differences were detected between conventionally prepared liver microsomes and those from livers perfused 1 hr with an erythrocytes-free medium under the conditions of open outflow. If the outflow pressure was increased artificially, the yield of microsomal protein decreased. The Vmax of both enzymes was markedly increased, whereas the Km values remained unchanged. The same microsomal alterations occurred when perfused rat livers were poisoned with phalloidin in vitro under the condition of open outflow. Our findings indicate that microsomal alterations in livers from poisoned animals might be due to microcirculatory disturbances, and not primary effects of the toxin on the endoplasmatic reticulum.