The existence of extrapineal locations for melatonin synthesis in the one-humped camel (Camelus dromedarius)

Abstract

We studied the sites of melatonin synthesis which was measured using the radioimmunoassay technique in the eye retina, skin, Harderian gland, liver tissue and jejunal mucosa in the immature and mature (non-rutting and rutting) Camelus dromedarius. For the first time, melatonin hormone was found in extrapineal sources in camel. These sites included the retina, skin, Harderian gland, liver and jejunal mucosa. The levels of melatonin in these sites reached 80.7, 33.5, 84.6, 548.9 and 2024.1 pg/mg, respectively, in the immature camel. In the mature non-rutting camel, during the non-mating season, the level of melatonin was estimated at 73.7, 41.1, 86.3, 1942.6 and 44112.0 pg/mg, respectively, giving a generally high level. In the mating rutting camel during the winter season, the melatonin level exhibited a level of 77.2, 39.5, 82.0, 930.9 and 14644.0 pg/mg, respectively, with an indication of a general decrease with the exception of the retinal melatonin when compared to the non-rutting camel. It should be noted that the finding of the melatonin hormone in the skin has never been recorded before, and has never been estimated before in other animals. The results in the present investigation also revealed that the wild plants upon which camels usually feed contain a significant amount of melatonin (838.2 pg/g in Chloris gayana and 226.6 pg/g in Anabasis setifera). This could be one of the factors causing an increase in the level of melatonin in the blood and consequently influencing testicular regression during the non-rutting season.

Keywords:

• Camelus dromedarius
• melatonin
• retina
• skin
• Harderian glands
• jejunum
• liver
• plants

Acknowledgement

This research has been funded by the General Directorates of Research Grants Programs, King AbdulAziz City For Science And Technology (KACST), Kingdom Of Saudi Arabia.