INCORPORATION BY THE KIDNEY OF FLUORESCENT PITUITARY HORMONES

Several Armour and NIH pituitary hormone preparations as well as other homologous serum protein fractions were labeled with fluorescent dyes (sulphorhodamine B, C.I. 45100, and fluorescein isothiocyanate). Rats were injected intravenously with the different labeled proteins and the animals killed at various intervals from 3 minutes to 10 days. Sections of the kidneys were studied under ultraviolet light (3,900 Å). It was observed that all the labeled proteins passed the glomerular filter and were accumulated by the cells of the proximal convoluted tubules. Labeled pituitary hormones were, in addition, reabsorbed by the thin limb and collecting tubules and appeared in the lumen of bladder. Filtration and reabsorption of proteins by the kidney can proceed independently of their nature and origin. All the proteins were reabsorbed with the same sequence, but pituitary hormones appeared faster and in larger amounts in the same sites of the nephron. They were also detected in the lumen of the ureter and in the bladder. It is assumed that the molecular weight of the proteins may play an important role, since the hormones' molecules were significantly smaller. It is remarkable that although the different hormones showed a preferential accumulation in the vessels of the corresponding target glands, they behave similarly in the kidney.