Circadian-Stage Dependent Acth1-17 Effect on DNA Synthesis in Murine Duodenum, Colon and Recum

Abstract

The objective was to determine the effect of adrenocorticotropin (ACTH 1-17) on the incorporation of [³H]TdR into DNA (DNA synthesis) in the duodenum, colon and rectum of CD2F, mice standardised to 12hr of light alternating with 12hr of darkness. A question asked was whether the difference in times of administration along the 24 -hr time scale influenced any response found. The response was complex as ACTH 1-17 was capable of bringing about statistically significant increases in the incorporation of [³H]TdR into DNA at certain times, decreases at other times, or no response at still another time. A generalization that can be made from all these tissues is that ACTH 1-17 had a greater influence in bringing about a decrease in DNA synthesis when it was administered around the time of transition from dark to light. A similar finding was made earlier for the ACTH 1–17 effect upon the tongue, esophagus and stomach.

A 2- and 3-way analysis of variance supports our conclusion that the kind-of-treatment, time-of-treatment and the interval-to-kill (Sampling time) as well as their interactions are important factors when determining any response of ACTH 1-17 or placebo.

Key Words:

• ACTH 1-17
• DNA
• circadian
• rhythm
• placebo
• duodenum
• colon
• rectum