The relationship between the plasma potassium concentration and renal potassium excretion in the adrenalectomized rat.
The purpose of this study was to evaluate the renal mechanisms which lead to a high urine [K+] in adrenalectomized (ADX) rats devoid of aldosterone. By dividing the urine [K+] by the urine to plasma osmolality ratio the [K+] in the cortical collecting duct luminal fluid can be estimated; dividing this value by the plasma [K+] yields an index of the transtubular [K+] gradient (TTKG) in vivo. The TTKG was close to 7 in aldosterone deficient ADX rats while on a normal K+ diet and fell towards unity when amiloride or a low K+ diet was administered to these rats. With a longer time on a low K+ diet, the TTKG was less than 1 in ADX rats. This suggests that K+ was reabsorbed in the medullary collecting duct under these conditions. Hyperkalaemia appears to have an 'aldosterone-like' action in the cortical collecting duct in vivo in the absence of aldosterone in ADX rats. This action of hyperkalaemia permits normal K+ excretion rates despite the absence of mineralocorticoids.
D000315:Adrenalectomy; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D006947:Hyperkalemia / Q000378:metabolism*; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D011188:Potassium / Q000652:urine*; D051381:Rats; D011919:Rats, Inbred Strains
D000584:Amiloride; D011188:Potassium