Studies of cholinesterase activity. VI. The depression of serum cholinesterase activity by a locally implanted human tumor in the guinea pig.

The study of glioblastoma multiforme in the anterior chamber of the guinea pig eye provided an unusual opportunity to observe the effect of a malignant but locally confined neoplasm on a serum enzyme system. Biochemically, these tumor-bearing guinea pigs were distinguishable from normal controls by a significant depression of serum cholinesterase activity. This observation substantiated the previously reported clinical phenomenon that many human patients with nonhepatic carcinoma had lowered cholinesterase activity in the absence of lowered serum albumin. The implications of this observation are discussed.