The In Vivo Effect of Angiotensin on the Proximal Tubular Reabsorption of Salt in Rat Kidneys

The purpose of the investigation presented in this report was to study the effect of angiotensin on the rate of proximal tubular reabsorption of filtrate in mammalian kidneys as evaluated from registration of the occlusion time, which is the time required from abruption of the renal circulation until the proximal tubules have completed reabsorption of the luminal filtrate. A direct momentary and rapidly reversible inhibitory effect of angiotensin is demonstrated the maximally depressed proximal reabsorption rate corresponding to the lowest rate observed in spontaneous variations of the glomerular filtration. The results indicate that a further depression of the glomerular filtration rate, below that corresponding to the. maximum effect of angiotensin, is caused by a reduction in the number of nephrons participating in urine formation. It is concluded that angiotensin, besides its vasoconstrictive effect, has a direct tubular inhibitory action, thus providing the two primary effects required for a hormonal regulator of renal blood flow, proximal reabsorption rate, and thereby of glomerular filtration rate.