A comparison of two cytochemical methods used to determine lysosomal function in cultured endothelial cells.

Two cytochemical methods were used to study the activation of acid phosphatase caused by acid incubation in intact cultured human endothelial cells. Using the Gomori lead capture method, there is a lag phase before enzyme activation, whereas using Barka & Anderson's diazonium salt simultaneous coupling method, there is not. As the lag period is due to the gradual loss of membrane restraint and indicates the original fragility of the membrane, this indicates that although the Barka & Anderson method is useful for studying the localization of lysosomal enzymes, the Gomori method should be used to study lysosomal membrane function. Pre-treatment with 100 microM histamine was found to increase lysosomal activation. The mechanism is not clear, but involves a labilizing effect on the membrane, indicted by a decreased lag time in the Gomori method.