Abstract. Using a continuous Percoll density gradient, endocrine cells of the anterior pituitary were separated. The cells were obtained from adult female Sprague-Dawley rats which had been ovariectomized for 7 days. The gradient revealed two equally sized populations of cells with densities of about 1.02 and 1.09 g/ml. Ninety-two per cent of the cellular GH content, 64% of LH, and 60% of TSH were found in the high density peak. Sixty-one per cent of the cellular Prl appeared in the low density peak. Immunocytochemical staining of the LH containing cells showed that 74% of the gonadotrophs were in the high density peak. After separation, the cells retained their responsiveness to LRH, TRH and GRF. Culture conditions influenced stimulated hormone release. Before stimulation, the cells were cultured either in tissue culture flasks (attached cells) or in Petri dishes (cells in suspension) for 3 days. After TRH-stimulation, suspended thyrotrophs released more TSH than attached thyrotrophs. Comparing the cells of both peaks, attached thyrotrophs of the high density peak showed higher stimulated TSH-release than those of the low density peak. The response of the gonadotrophs and somatotrophs to stimulation did not differ when culture conditions were changed. The present results demonstrate that the secretory activity of endocrine cells is influenced by culture conditions and should be evaluated fore each cell type.
A novel approach to stabilize fetal cell-free DNA fraction in maternal blood samples for extended period of time