Aims: 

Different response of Lewis and Fischer 344 rat strains to induction of inflammation could be affected not only by activity of hypothalamo-pituitary-adrenal axis but also by the changes in plasma levels of hormones with immunoregulatory action. The study was aimed to compare the changes in plasma hormone levels involved in the response to stress exposure in both rat strains.

Methods: 

Adult rat males of Lewis (LEW) and Fischer 344 (FIS) strain (8 animals/group) were exposed to restrain stress for 2 hours. Blood samples were collected (5, 20 and 120 min of stress) from cannulated tail artery. Control animals were without exposure to stressor. Corticosterone (CS), testosterone (TE), dehydroepiandrosterone (DHEA), 17b-estradiol (ES) and progesterone (PGS) were determined by radioimmunoassay, epinephrine (E) and norepinephrine (NE) levels by radioenzymatic method.

Results: 

The levels of plasma CS (LEW: 21.3 ± 0.7, FIS: 39.9 ± 3.2 mg/100ml; p < 0.05), E (LEW: 450 ± 50, FIS 2050 ± 650 pg/ml in 20 min stress; p < 0.05) and NE levels after stress exposure were significantly higher in FIS as compared to LEW rats. Decrease of TE levels was noted after exposure to stress. However, the difference of TE concentration in control and stressed rats were higher in LEW rats (0.90 in FIS and 3.50 ng/ml in LEW, p < 0.05). No strain differences were observed in DHEA levels. Lower levels of ES (FIS: 37 ± 2 pg/ml, LEW: 49 ± 5 pg/ml; p < 0.05) and higher values of PGS plasma levels (FIS: 3.11 ± 0.80 ng/ml, LEW: 0.29 ± 0.12 ng/ml; p < 0.05) were noted in FIS rats after stress.

Conclusion: 

These results demonstrated the differences in the response of CS, E, NE, and gonadal steroids after exposure to stress in LEW and FIS rats with lower levels of hormones with anti-inflammatory action in LEW rats.

Supported by grant APVT 21 008602.