Pineal modulation of ACTH 1-17 effect upon murine corticosterone production

In tests of Corticosterone production in vitro, aqueous pineal homogenate (APH) modulates the effect of a short-chain ACTH analogue, ACTH 1-17, added to adrenals from different circadian stages. Adrenal and pineal glands from female B6D2F₁ mice, standardized on staggered LD 12:12 regimens, were obtained at the same clock-hour from each room, in order to cover 6 different circadian stages. Adrenals from each circadian stage were bisected and incubated with APH from the same circadian stage (isophasic incubation) or from one of the other 5 circadian stages (heterophasic incubation). ACTH 1-17 (0.05 IU) was added to each incubation medium. After 4 hours of incubation at 37°C with 95% O₂ and 5% CO₂, the media were stored at -20°C until Corticosterone RIA were done. APH was found to have a statistically significant modulatory effect upon the stimulation by ACTH 1-17 of adrenal Corticosterone production in vitro. This APH effect changed rhythmically as a function of circadian stage from amplification over no effect to attenuation, as a so-called feed-sideward.