Escape from the Sodium-Retaining Action of Intrarenal Angiotensins II and III in the Conscious Dog*

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Abstract
The maximum amounts of angiotensin II and III that were confined to the kidney during intrarenal arterial administration in conscious dogs were determined to be 2 and 12 pmol/kg .cntdot. min, respectively. These dogs were infused chronically intrarenally to uninephrectomized dogs. A significant reduction in urinary volume and excretion of sodium was observed at 24 h of the intrarenal peptide infusions. These excretory effects were more marked with angiotension III than with angiotensin II. Escape from the antidiuretic and antinatriuretic effects of angiotensin II and III was observed after 24 h in spite of continuous administration of the peptides. To define the role of reduced intrarenal angiotensin concentration in the physiological phenomenon of escape from the sodium-retaining action of mineralocorticoids, angiotensin II or III at the above dose was administered intrarenally together with 11-deoxycorticosterone acetate. No delay in escape from the sodium-retaining effects of the mineralocorticoid was noted as a result of concurrent intrarenal angiotensin administration. In conclusion, both angiotensin II and angiotensin III have direct sodium- and volume-retaining effects on the kidney. These renal effects are abolished within 48 h, either due to tachyphylaxis to angiotensins or by other mechanisms overriding the actions of angiotensins. No association was demonstrated between suppression of the renin-angiotensin system and escape from mineralocorticoid-induced sodium retention.