Effects of melatonin on the process of apoptosis in rat thyroid follicular cells.

OBJECTIVES: Apoptosis, or programmed cell death, is a normal component in the development of multicellular organisms and is essential for many physiological processes. Apoptosis is a process in which cells play an active role in their own death (apoptosis is often referred to as "cell suicide"). Disturbances of apoptosis regulation can result in many diseases. Certain substances (for example--aflatoxin B1; AFB1) can induce apoptosis in various organs and tissues. Melatonin (Mel) is a hormone (indoleamine) which has antioxidant, antiproliferative and, potentially, anticancerogenic activities. The aim of our study was to examine the influence of late-afternoon (1600-1800) intraperitoneal (i.p.) Mel injections, administered for 3 weeks, on the process of apoptosis in male Wistar rat thyroid follicular cells (TFC); Mel was injected alone or together with AFB1 (i.p., also once daily for 3 weeks).

METHODS: In order to assess the process of apoptosis, evaluated in microscopic preparations of rat thyroids, an In Situ Cell Death Detection, POD Kit [Roche, GER] and the DAKO Liquid DAB Substrate-Chromogen System [DakoCytomation, USA] were employed.

RESULTS: Aflatoxin B1 increased the apoptotic index (I(apopt)) in rat TFC, in comparison to controls (p<0.001). The I(apopt) value in the rats, receiving Mel and AFB1 injections, was statistically lower, as compared to the value of the examined index in the group of AFB1-treated animals (p<0.001). No statistically significant differences of I(apopt) value were observed between the Mel-treated group of animals and the controls.

CONCLUSION: Melatonin can assumingly regulate the growth of cells and tissues by influencing the process of apoptosis.