Seasonal changes of the structure and function of prolactin cells in the pituitary gland of Vipera berus (L.).

A selective staining by the indirect immunofluorescence method has been used for prolactin cells (PRL-cells) in the pituitary gland of Vipera berus (L.). The PRL-cells showed significant seasonal changes as judged by their morphological features, their number and localization in the pars distails. In the functional cycle of the cells 4 periods could be distinguished: 1 -- spring (March --May), when the release of the hormone as well as its increasing accumulation were observed; 2 -- early summer (June -- July), when the accumulation of the hormone in the gland reached the maximum and prevailed the release; 3 -- late summer (August), when was observed a rapid PRL release with a simultaneous exhaustion of cell reserves: 4 -- autumn (September), was characterized by small PRL content in the cells and its inconsiderable release.