Aims: 

The avian pineal is directly photosensitive due to the presence of photopigments, among which pinopsin seems to be one of the most important and responsible for acute influence of light on the pinealocyte activity. Up till now, pinopsin has been detected in the chicken and the Japanese quail. The purpose of our study was to check the presence and distribution of pinopsin in the pineals of domestic turkeys at various stages of postembryonic life and as in cultured pinealocytes.

Methods: 

Pineals of 1-day-, 2-, 14-, 22- and 56-week-old turkeys as well as monolayer cultures of turkey pineal cells were fixed and subjected to immunohistochemical staining with primary antibody against pinopsin.

Results: 

The pinopsin-immunoreactivity was observed in apical processes of rudimentary-receptor pinealocytes limiting the follicular lumen and in short processes originating from secretory pinealocytes laying in outer layer of the follicular wall in the pineals of turkeys from 1 day to 1 year old. The number of secretory pinealocytes with pinopsin-positive processes increased with age. In monolayer cultures, the positive staining for pinopsin was observed in pinealocytes. It was especially prominent in short cytoplasmic processes originating from cytoplasmic pools of cells.

Conclusions: 

Pinopsin is present in turkey pineal glands during the whole period of postembryonic life and shows very specific distribution.