Alterations in patterns of excretion and other metabolic functions in developing fish embryos exposed to benzo(a)pyrene

Abstract

Steelhead trout(Salmo gairdneri) embryos were used as a model to study some of the physiological and biochemical changes which occur following exposure to sublethal levels of benzo(a)pyrene B(a)P, a known environmental contaminant. Embryos were exposed to B(a)P on day 1, 15, or 25 post fertilization, corresponding to the pre-blastula, eyed stage and late organogenesis stage of development. These times were chosen to determine whether the age of the embryo at the time of exposure influenced their response to this model compound. The changes which were observed were related to the age of the embryo at the time of exposure but not to the concentration of the B(a)P to which they were exposed. It was found that the longer the embryo developed, the more permeable the eggs became, taking up twice to 10 times as much B(a)P on day 25 as they did on day 1. Embryos exposed later in development were also able to excrete the metabolites of B(a)P through the egg membrane 10 times more rapidly than their counterparts which were exposed early during development. Following hatching, the larvae from those groups exposed later in development contained 2 to 5 times as much B(a)P bound to or dissolved in the tissues than did those exposed on day 1. Hatching time was also modified by the times of exposure, with those exposed on days 15 and 25 hatching later and over a longer period of time than either the untreated or DMSO controls. Although physical abnormalities were rare, there appeared to be a consistent increase in the level of teratogenesis in those groups which were exposed early during development.