Influence of age on isolation stress‐stimulated carcinogen‐metabolizing enzymes of rats

Abstract

Rats aged 6, 12, 24, 36, and 52 weeks were subjected to social isolation for 4 days, while littermates housed in groups of six for the same period served as controls. The isolation treatment resulted in a 2-fold increase in the serum corticosterone level of all except the youngest animals in whom the hormone level was greater than 4 times that of their agematched controls. Hepatic rnicrosomal protein was highest in the 24-week-old rats and lowest in the rats aged 52 weeks. The levels of most of the enzymes measured were lowest in the 6-and 52-week-old animals. No significant differences in microsomal protein, cytochrome P,,,, epoxide hydrolase, UDPGA transferase, or glutathione transferase were observed between the isolated and control animals. The stress treatment increased aryl hydrocarbon hydroxylase levels of the rats aged 6, 36, and 52 weeks by loo%, 50%, and 33% respectively. The microsomes prepared from livers of isolated 6-week-old animals catalyzed the binding of significantly higher amounts of pH]-benzo(a)pyrene to DNA than controls.

The influence of cold‐restraint stress on some components of the antioxidant defence system in the tissues of rats of various ages

“…Therefore, in the present experiment the stress-induced elevations in lipoperoxide and decreased GSH levels occurred, predictably, in the liver. Previous reports have indicated that the susceptibility of the P450-dependent oxidases to stress is influenced by a number of factors, in particular the age of the subject (Capel et al, 1981;Rikans and Notley, 1982). Younger animals also have greater resistance to lipoperoxide formation (Sharma, 1977;Player et al, 1977) and have higher GSH levels in many tissues (Abraham et al, 1978).…”

“…However, GSH levels also decrease with increasing age (Abraham et al, 1978). In addition, differences in the "susceptibility to stressful stimuli," resulting in quantitative differences in metabolic response, have been observed in animals of differing ages (Capel et al, 1981;Rikans and Notley, 1982). Thus, the present study was conducted with groups of rats of differing ages within the range most commonly employed in previous investigations.…”

Evidence of α2-adrenoceptor involvement in B[α]P induction processes of drug-metabolizing enzymes: the effect of stress

“…Several pathways exist for enzyme-catalyzed xenobiotic biotransformation in the liver, and these pathways are modulated by a large number of environmental and hormonal factors. Among the factors which modulate cytochromes CYP and other drug-metabolizing enzymes are psychological or physiological stress (7)(8)(9). It is noteworthy that animals exposed to conditions of psychological or physiological stress are vulnerable to different pathogenic factors such as the reactive derivatives of drugs, which can stimulate mutagenic or carcinogenic processes (10).…”