Renal response of newborn dog to potassium loading

The renal response to potassium loading was studied in 14 newborn (6-20 days of age) and 14 adult mongrel dogs in order to determine the capacity of the newborn to excrete potassium load. Eight newborn and eight adult dogs were infused with 20 mueq of potassium chloride X min-1 X kg body wt-1 for 240 min. Adults excreted a significantly greater proportion of the potassium load during the 240-min infusion than did newborns (72 +/- 4 vs. 52 +/- 4%, P = 0.003). The infusion resulted in a significantly greater increase in plasma potassium concentration in the newborn (3.9 +/- 0.3 meq/liter) than in the adult (2.8 +/- 0.4 meq/liter), P = 0.05. Average potassium excretion rate per body weight was greater in the adult than newborn during potassium loading (15.0 +/- 1.0 vs. 10.4 +/- 0.7 mu eq X min-1. kg body wt-1, P = 0.003); however, average potassium excretion corrected for glomerular filtration rate was not significantly different between the adult and newborn (3.2 +/- 0.2 vs. 3.0 +/- 0.2 mu eq/ml filtered, P greater than 0.20). In another six newborn and six adult dogs, blockade of distal nephron potassium secretion with amiloride in the potassium-loaded state inhibited more than 90% of potassium excretion in both the newborn and adult.(ABSTRACT TRUNCATED AT 250 WORDS)