Peritoneal plasmacytomagenesis in mice: comparison of different pristane dose regimens.

Plasmacytomas were induced in inbred BALB/c pi mice by the ip injection of pristane with 4 different dose schedules. Three 0.5-ml doses (1.5 ml) given at 2-month intervals gave an average yield of 61% plasmacytomas in 6 experimental groups with a range from 51 to 71%; a single 1-ml dose gave an average yield of 42% plasmacytomas in 5 experimental groups with a range from 37 to 45%; and a single 0.5-ml dose gave an average of 22% from 3 experiments involving young mice with a range from 14 to 26%. Two 0.5-ml doses given at various intervals from 14 to 300 days gave yields of plasmacytomas that usually but not always were greater than that obtained with a single 0.5-ml dose of pristane. When the second injection of pristane was delayed as long as 180 days, a strong additive effect over that observed with 0.5 ml alone was obtained. The plasmacytomas developed in mice given the second dose 180 days after the first, with virtually the same latent period as observed with a single 1-ml dose. No plasmacytomas were found in 200 BALB/c pi mice inoculated with corn oil, aluminum hydroxide, or very small doses of pristane (i.e., 0.05 ml). The minimal latent period for plasmacytoma development is about 120 days. The median latent period ranged from 180 to 250 days in the groups of mice that received 3 0.5-ml injections of pristane. In a single experiment pristane freed of UV-absorbing materials was as potent as commercial grade pristane in inducing plasmacytomas.