Effect of oligopeptides - homologues of the fragment of acth15-18 on morphogenetic markers of stress in the adrenal glands on the model of acute cold injury in rats

INTRODUCTION: The study’s aim was to evaluate stress-protective effect of oligopeptides-homologues of the ACTH fragment 15-18 on morphogenetic signs of stress reaction of the adrenal glands under acute cold exposure in rats.
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 the 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 Semax were administered intranasally in a dose of 20 mcg/kg 30 minutes before and after cold exposure. Rectal temperature was measured before and 10 minutes after cold exposure. Zona glomeruloza, zona fasciculata, zona reticularis, and the area of cells and nuclei of adrenocorticocytes of zona fasciculate were measured.
RESULTS: KK-1 significantly prevented structural changes in the adrenal cortex and medulla, stabilized the secretory activity of glucocorticoid-producing cells. However, the congestion of capillaries of 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 more marked recovery of the adrenal glands (a greater saturation of cytoplasm of adrenocorticocytes of zona glomerulosa and zona fasciculate). 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 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 Semax.
DISCUSSION AND 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 to the peptide KK-1. Both studied substances exceeded the reference medicine Semax. KK-5 is a promising stressprotector and frigoprotector.