THE CELL BLOT ASSAY IN ANALYSIS OF RAT ANTERIOR-PITUITARY CELL SECRETION

We have investigated the efficacy of the cell blot assay in analysis o f the secretion of hormones and peptides from rat anterior pituitary c ells. The dissociated cells are cultured on pieces of translucent poly vinylidene difluoride membrane, on which their secretory products are adsorbed and subsequently immunostained. The area and integrated optic al density of the stained `halo' surrounding individual cells is measu red by microscopical image processing and the values for basal secreti on of a particular hormone or peptide are compared with those after ap plication of secretagogues or inhibitors. Our experiments tested estab lished responses of dissociated rat anterior pituitary cells; in gener al, the results were as expected. Double immunoenzymatic staining coul d be used to show secretion of two products from the same or different cells in one preparation, and immunofluorescence with fluorescein- an d/or rhodamine-labelled antibodies could be used instead of enzyme-lin ked immunolabelling. Optimal dilutions of immunoreagents were much hig her than those used for immunocytochemistry on tissue sections. Althou gh the cell blot assay does not provide absolute quantification, since some of the secreted product escapes into the medium, it is a relativ ely easy and economical way for morphologists to compare secretion fro m individual cells under varying conditions.