The Effect of Plasma Potassium in Determining Normal Rates of Excretion of Potassium in Dogs

Abstract

Increased excretion of K was accompanied by a small increase in Na excretion.Excretion of both Cl and HCO3 increased, Cl more after KCI, and HCO3 more after KHCO3.The results indicate that within normal ranges, plasma K is an important factor determining the rate of excretion of K. Existing investigation of K excretion has led to two general conclusions:firstly, that under normal conditions the rate of excretion of K is less than 30% of the amount filtered at the glomeruli and there must therefore be proximal tubular reabsorption of K; secondly, that under abnormal conditions of K loading, renal failure, some diuretics etc., the rate of excretion of K can exceed the amount filtered and there must then be distal tubular secretion of K. Current theory proceeds further to propose that under all circumstances proximal reabsorption is nearly complete and that the K normally appearing in the urine is due to secretion in the distal tubules. The evidence for these concepts has been reviewed by Berliner and Brenner [1973] and Schultze [1973].

The Effect of the Anions, Phosphate and Sulphate, on Normal Rates of Excretion of Potassium in Dogs

“…After KH2PO2 or K2SO4, the urinary anion was P04 or SO4, instead of Cl and HCO3. Any effect of anions on K excretion was much less than the effect of increase in plasma K.At low rates of excretion of K, increased urinary excretion of impermeant anion can determine increased excretion of K. However, the effect of anion is small in comparison with the effect of increase in plasma K.In a previous paper, Baylis and O'Connor [1976] described the changes in blood and urine produced by small doses of KCI or KHCO3 given to normal conscious dogs, and reached the conclusion that, with K excretion close to normal rates, plasma K is an important determinant of K excretion. This paper is concerned with the possible effect of urinary anions in determining excretion of K. In the experiments of Baylis and O'Connor [1976], K in the urine was accompanied by Cl and HCO3.…”

“…Several authors have indicated that K excretion may be increased by impermeant anions such as ferricyanide and sulphate [Berliner, Kennedy and Hilton, 1950;Cort and McCance, 1954;Sullivan, Wilde and Malvin, 1960] but they had used large doses of the salts to produce rates of excretion far greater than occur normally. The purpose of this paper is to study the effect of SO4 and P04 on K excretion close to the normal rates of excretion of the anions and of K. The changes in plasma and urine produced by small doses of (NH 4)2 HPO4, KH2PO4 and K2SO4 have been recorded and the excretion of K compared with that observed by Baylis and O'Connor [1976] after doses of KCl 342 Baylis and O'Connor and KHCO3. Incidental to the main purpose, data was also obtained concerning the excretion of PO4 and SO4.…”

“…In a previous paper, Baylis and O'Connor [1976] described the changes in blood and urine produced by small doses of KCI or KHCO3 given to normal conscious dogs, and reached the conclusion that, with K excretion close to normal rates, plasma K is an important determinant of K excretion. This paper is concerned with the possible effect of urinary anions in determining excretion of K. In the experiments of Baylis and O'Connor [1976], K in the urine was accompanied by Cl and HCO3.…”

“…In a previous paper, Baylis and O'Connor [1976] described the changes in blood and urine produced by small doses of KCI or KHCO3 given to normal conscious dogs, and reached the conclusion that, with K excretion close to normal rates, plasma K is an important determinant of K excretion.…”

“…This paper is concerned with the possible effect of urinary anions in determining excretion of K. In the experiments of Baylis and O'Connor [1976], K in the urine was accompanied by Cl and HCO3. However, SO4 and P04 normally constitute 70 % of the anion in the urine of dogs.…”