Localization of Tamm-Horsfall glycoprotein in the normal rat kidney and the effect of adrenalectomy on its localization in the hamster and rat kidney.
Immunofluorescence and immunoperoxidase techniques were used to study the localization of Tamm-Horsfall glycoprotein in the normal rat kidney. In the fluorescence microscopical preparations, the glycoprotein was observed in the thick ascending limbs of the loops of Henle and distal convoluted tubules and was thus, in general, similar to our earlier observations on the hamster and man. The situation in the maculae densae was, however, somewhat different, for in the rat the majority of them were seen to possess Tamm-Horsfall glycoprotein on the luminal surfaces of their cells and only a small proportion resembled the hamster and man in lacking it. These observations were confirmed by the immuno-electron microscope technique. Furthermore, it was shown that in the thick ascending limbs and distal convoluted tubules, Tamm-Horsfall glycoprotein is associated with the total plasma membrane systems of its cells. Thus it appears that Tamm-Horsfall glycoprotein is confined to that part of the nephron responsible for the process of urine dilution. As this function is, at least in part, regulated by adrenal cortical hormones, the effect of adrenalectomy on the distribution of the glycoprotein was studied. The results obtained showed varying degrees of disappearance of Tamm-Horsfall glycoprotein in the kidneys of adrenalectomized hamsters, initially from the distal convoluted tubules and later from the thick ascending limbs. In the rat, on the other hand, the effect of adrenalectomy on Tamm-Horsfall glycoprotein was much less pronounced, possibly due to the presence of secondary adrenal tissue. The possible physiological significance of these findings is discussed.