Ultracytochemical localization of calcium ions in the pineal organ of the domestic turkey Ultracytochemiczna lokalizacja jonów wapniowych w szyszynce indyka
Calcium ions are involved in several processes occurring in the avian pineal, including
the regulation of melatonin secretion. The aim of study was to investigate distribution of
calcium ions in the pineal organ of domestic turkey at the level of electron microscopy.
The study was performed on 12 female turkeys housed in a cycle of 12L : 12 D (light
intensity 300 lux; 07:00 – 19:00), starting from the third week of life. At the age of 12 weeks,
the birds were anesthetized with halothane and sacrificed by decapitation at 14:00
and at 02:00 (in darkness). The pineals were fixed using the potassium pyroantimonate
method, which enables visualization of calcium ions in the form of electron dense precipitates.
Extremely numerous, large precipitates of calcium pyroantimonate were observed between
collagen fibres of the connective tissue surrounding the pineal follicles. The number
of precipitates in the follicles was much lower than in the neighbouring stroma. Precipitates
were numerous in intercellular spaces between cells forming the follicular wall. In contrast,
they were infrequently observed in the follicular lumen. In pinealocytes, large amounts
of precipitates were present in the nucleus, mitochondria and short, wide cisterns
of the smooth endoplasmic reticulum. Precipitates were sparse in the apical prolongations
of rudimentary-receptor pinealocytes. The content of precipitates did not differ prominently
between individual pinealocytes. Precipitates in the cytosol of both rudimentary-receptor
pinealocytes and secretory pinealocytes were much more numerous in the organs taken
ex vivo during nighttime than during daytime. Supporting cells contained much fewer
precipitates than pinealocytes.
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