Effects of ACTH and corticosteroids on phenylethanoIamine‐N‐methyltransferase (PNMT) expression as determined by immunocytochemical localization in the adrenal gland of the lizard Podarcis sicula

Abstract

This study was undertaken to investigate whether, in the lizard Podarcis sicula, the expression of adrenaline synthesizing enzyme phenylethanolamine‐N‐methyltransferase (PNMT) is influenced by variations in corticosteroid levels. Adrenal glands of specimens treated with ACTH or corticosteroids were collected and stained with avidin‐biotin complex (ABC) and immunogold techniques, for light and electron microscopical observations, respectively. In non treated specimens, positive staining was mainly confined to the catecholamine containing cells (adrenaline cells), located closer to the steroidogenic ones. In treated specimens, instead, positive staining was found in all the cells of the ehromaffin portion of the gland (adrenaline and noradrenaline cells). Immunoelec‐tron microscopy confirmed the distribution of immunoreactive cells observed at the light microscope. These results support the hypothesis that corticosteroids regulate PNMT expression in reptilian adrenal glands similarly to what occurs in mammals.

Key words:

• Mealybug
• Adrenal gland
• Phenylethanolamine‐N‐methyltransferase
• Immunocytochemistry
• ACTH
• Corticosteroids