Immunocytochemical demonstration of day/night changes of clock gene protein levels in the murine adrenal gland: differences between melatonin‐proficient (C3H) and melatonin‐deficient (C57BL) mice

The expression of clock gene proteins PER1, BMAL1, and CRY2 in the adrenal gland varies significantly across a 12-hr light/dark cycle.

• In C3H mice, levels of PER1 and CRY2 proteins peaked during the light phase, while BMAL1 levels peaked during the dark phase.
• The adrenal medulla of C57BL mice exhibited similar patterns of clock gene protein expression as C3H mice.
• In contrast, the adrenal cortex of C57BL mice showed consistently lower levels of clock gene proteins without time-dependent variation.
• These findings suggest that the adrenal gland functions as a peripheral oscillator in mice.
• Melatonin may play a role in modulating clock gene protein levels in the adrenal cortex.

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