A Gompertz age-specific mortality rate model of aging, hormesis, and toxicity: fixed-dose studies.

Based on the proposition that the logarithm of age-specific mortality rate (Gompertzian) is a linear measure of the mean intensity of injury for a homogeneous mammalian population in a uniform environment, a model was developed which characterizes mortality experience resulting from both toxic and hormetic actions. The mortality-reducing component (longevity hormesis) was assumed to be reversible; toxic effects, on the other hand, were assumed to accumulate irreversibly. Following chronic low-dose administration of selected toxic substances, it was demonstrated (in certain cases) that longevity hormesis could enhance lifespan, even in the presence of concomitant toxicity. Even when toxicity was evident, hormesis could ameliorate some of the mortality. The assumption that high-dose chronic toxicity studies can generate realistic estimates of risk at low doses is challenged.