THE QUESTION OF WATER REABSORPTION BY THE RENAL TUBULE AND ITS BEARING ON THE PROBLEM OF TUBULAR SECRETION

Abstract

The head of pressure in the glomerular capsules of Necturus calculated by Poiseuille''s equation was found to agree substantially with the observed intracapsular pressure. The conclusion is drawn that there is no significant exchange of water between the tubule wall and lumen. The propulsive action of the cilia lowers the intracapsular pressure by only 12-23% Since the phosphate concentration of the bladder urine may be several times that of the glomerular fluid it is concluded that the tubule cells secrete phosphate. Reabsorption of water is not essential to a reabsorption of glucose or chloride. The loop of Henle is probably the chief site of water reabsorption in the mammalian tubule.