Induction of Amyloidosis in Mice: Preparation of Active Azocasein (AZO) and Effect of Endotoxin (LPS).

Abstract

Frequent failure to induce amyloidosis in mice with multiple injections of casein prompted this study to compare the effectiveness of AZO prepared and sterilized by various methods. The direct effect of LPS contamination of AZO was determined by comparing four protocols all including daily subcutaneous (s.c.) injections of AZO for 20 days; a) no other injections; b) daily intraperitoneal (i.p.) injections of 10μg LPS; c) a single initial i.p. injection of 10μg LPS; and d) daily i.p. injections of 10μg LPS. Daily i.p. injections of 10μg LPS had no additional effect on amyloid induction when compared to AZO alone. With both C57B1 and CBA/J mice, daily 10μg LPS injections protected against amyloid deposition. With C57B1 mice, both severity and incidence of amyloid were reduced. With CBA/J mice, the severity of amyloid deposition was reduced, but not the incidence. The three types of casein derivatized to prepare AZO (purified grade, or technical grade with one or with two precipitations) resulted in a progressively increasing incidence of amyloidosis. After derivatization of casein to AZO and concentration by ultrafiltration, sterilization by autoclaving or filtration produced a less-effective material than sterilization by exposure to diethyl pyrocarbonate (DEP).