Abstract
Follicle-stimulating and luteinizing hormones were labeled with fluorescein isothiocyanate, rhodamine B and ferritin. The histologic distribution of labeled hormones, injected intravenously into adult rats, was studied by means of fluorescence microscopy and Prussian blue reaction for ferritin-conjugated products. As controls, rats were injected with free labels, denatured labeled hormones and unlabeled hormones mixed with labels. As a result of labeling, a variable loss in biologic activity occurred. After injection of labeled hormones a fluorescent or blue colored material appeared in testicular and epididymal tissue, but was absent in other endocrine glands. Macrophages in the organs studied and kidney tubular cells showed accumulations of the same material. Five minutes to 3 hr after injection, labeled products were seen in vessels and extravascular connective tissue of the testis. Labeled follicle-stimulating hormone appeared in the tubule wall, in a few Leydig cells, in Sertoli cells and in some spermatogonial cells, while labeled luteinizing hormone was selectively localized in Leydig cells and fibroblast-like cells of the tubule wall. Control experiments revealed the presence of similar material in the vessels of testis and in Leydig cells and macrophages of other organs. Specificity based upon the heterologous origin of hormones, partial denaturation by tagging, the role of Sertoli cells in the accumulation of proteins and the phagocytic properties of Leydig cells is discussed.