RESUMO
Objectives: Aim of the current study was to evaluate the stress-protective effect of oligopeptides-homologues of the adrenocorticotropic hormone (ACTH) fragment 15-18 on morphogenetic signs of stress reaction of the adrenal glands under acute cold exposure (CE) in rats. Materials and Methods: The acute cold stress was reproduced by placing random-bred male rats in a freezer at a temperature of -18°C for 2 hours. The peptides-homologous of ACTH15-18 acetyl-(D-Lys)-Lys-Arg-Arg-amide (KK-1) and acetyl-(D-Lys)-Lys-(D-Arg)-Arg-amide (KK-5) and the reference medicine (Sema) were administered intranasally in a dose of 20 mg/kg 30 minutes before and after CE. Rectal temperature was measured before and 10 min after CE. Zona glomeruloza, zona fasciculata, zona reticularis, and the area of cells and nuclei of adrenocorticocytes of the zona fasciculata were measured. Results: KK-1 significantly prevented structural changes in the adrenal cortex and medulla and stabilized the secretory activity of glucocorticoid-producing cells. However, the congestion of the capillaries of the zona fasciculata and zona reticularis remained in some locations. Zona fasciculata cells had a marked tendency to decrease, and the area of nuclei significantly decreased (p<0.05) recovering the width to control animals' markers. KK-5 had a more marked recovery of the adrenal glands (a greater saturation of cytoplasm of adrenocorticocytes of zona glomerulosa and zona fasciculata). The number of chromaffin cells at rest was increased in the adrenal medulla. KK-5 statistically significantly normalized both the area of cells (p<0.05) and the area of nuclei (p<0.05) of the zona fasciculata, unlike KK-1, which reliably restored only the marker of the nuclei area. Some morphometric parameters of acute stress hypertrophy remained in the adrenal glands of rats receiving Sema. Conclusion: KK-1 and KK-5 prevented the manifestation of acute stress reactions in the adrenal cortex of rats. KK-5 had a more marked stress-protective effect compared with the peptide KK-1. Both study substances exceeded the reference medicine Sema. KK-5 is a promising stres-sprotector and frigoprotector.
RESUMO
NSAIDs are promising agents for preventing cold injury (frigoprotectors). The influence of prophylactic administration of the non-selective COX inhibitor diclofenac sodium (7 mg/kg) and the highly selective COX-2 inhibitor etoricoxib (5 mg/kg) on cyclooxygenase pathway biomarkers was studied on the model of acute general cooling (air hypothermia at -18 °С for 2 hours). Diclofenac completely prevented a decrease in body temperature, surpassing etoricoxib. In the liver of the rats immediately after cold exposure, the content of COX-1 was increased moderately and the content of COX-2 highly significantly. Very significantly, the level of PGE2 decreased, and the levels of PGF2α, especially PGI2 and TXB2, were elevated. In the blood serum, the level of COX-1 was decreased, and the changes in COX-2 and prostaglandins levels were similar to those in the liver. Diclofenac exerted a moderate effect towards the normalization of both COX isoforms in the liver, moderately increased the content of PGE2, and decreased - PGF2α and TXB2 without changing the level of PGI2. In serum, diclofenac reduced COX-1 level to subnormal values, and its effect on other biomarkers was similar to that in the liver, except for a moderate decrease in PGI2. Thus, diclofenac was inferior to etoricoxib, which normalized COX-1, COX-2, PGE2, and PGI2 in the liver and reduced the content of PGF2α and TXB2 in the liver to subnormal values. At the same time, in the blood serum, it decreased COX-1, COX-2, and PGE2 to subnormal values, normalized PGF2α, and PGI2, and significantly reduced TXB2. The opposite degree of intensity of the influence of diclofenac and etoricoxib on the cyclooxygenase pathway and body temperature indicates a dissociation of anti-inflammatory and frigoprotective activity. Inhibition of oxidative stress is not determinative for the frigoprotective activity of NSAIDs since diclofenac, despite the weaker influence on the content of 8-isoprostane in the liver, still exerts the maximum frigoprotective activity.
