The overall objective of this project is to develop cell model systems with which to study hormone synthesis by endocrine cells in culture. The hormone-producing cells to be utilized include the JEG lines of human choriocarcinoma cells which produce the steroid hormone, progesterone, and which convert appropriate 19-carbon precursors to estradiol. These cells also synthesize the glycoprotein hormone, chorionic gonadotropin, and another protein hormone, chorionic somatomammotropin. Rat pituitary tumor cells which synthesize growth hormone in culture will also be used for these studies. New cell strains from hormone-synthesizing tissue will be developed. Two major techniques will be used to modify hormone production by the cells in culture. 1) Cell hybridization between hormone-producing cells and non-endocrine cells will be accomplished by fusing the cells and placing them in special selective medium for the development of hybrid strains. 2) Treatment with mutagenic agents will also be used to alter hormone production. The modified strains will be examined for hormone synthesis by using new chromatographic and immunological assays for hormones and hormone subunits. Steroid synthesis will be examined by radioimmunoassay, conversion of specific labeled precursors into steroids, and by complementation techniques for correction of enzyme deficiencies in the pathways of steroid synthesis. The chromosomes of the various cell strains will be identified by special staining techniques and specialized functions correlated with the presence or absence of specific chromosomes. The hormone-producing cell strains will be used to assign genes coding for synthesis of specific hormone subunits or enzymes required for hormone synthesis to specific chromosomes. The control and process of hormone synthesis will be examined in the modified cell strains.