Pyrene strain effects

The effect of curvature on the aromatic character of polyaromatic hydrocarbons (PAHs) can be studied by comparing planar PAHs and their curved analogues. In order to address this issue a variety of [n](2,7)pyrenophanes (n = 7-10) in which the pyrene (22) moiety is strongly distorted from planarity have been synthesized and studied45. The degree of distortion from planarity and therefore the strain in these systems is controlled by the length and type of the tether that connects the two remote ends (positions 2 and 7) of 22. 

Benzo[a]pyrene-induced skin tumors were decreased in diet restricted ABC, C57, and Swiss strains of mice. Interestingly, it was demonstrated that the decrease in tumor incidence is independent of any particular source of calories. Contrary to the popular belief of low-fat or low-carb diets, it was demonstrated that decrease in cancers following DR depends mainly upon reduction in the total number of calories rather than decrease in calories coming from either only fat or carbohydrates. Since the first reports in the 1940s to 1950s, the anticarcinogenic effect of DR on chemical-induced tumors has been extensively studied in various tissues and after exposure to a variety of chemicals. 

No studies were located regarding reproductive effects in humans following oral exposure to the PAHs discussed in this profile. Three animal studies were located that evaluated the reproductive effects of benzo[a]pyrene in animals. The results of two oral studies in mice (Mackenzie and Angevine 1981 Rigdon and Neal 1965) and one in rats (Rigdon and Rennels 1964) indicate that benzo[a]pyrene induces reproductive toxicity in animals. The incidence and severity of these effects depends on the strain, method of administration, and dose levels used. In one study,... 

In mice, the tumorigenic dose of benzo[a]pyrene is dependent on the strain. For example. Habs et al. (1980) tested 1.7-4.6 pg benzo[a]pyrene (0.016-0.04 mg/kg/day) in order to determine its dose-response relationship as a carcinogen when topically applied to the backs of NMRI mice throughout their lifetimes. A clear-cut dose-response relationship was seen for benzo[a]pyrene and the induction of tumors. The lowest dose at which skin tumors appeared was 1.7 pg (0.016 mg/kg/day). This strain of NMRI mice also has a high (70%) background incidence rate of systemic tumors, so an evaluation of the effects of benzo[a]pyrene on any organ other than the site of administration was not possible. 

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