Effects of Low-Potassium Diet on N-Ethylmaleimide-Sensitive ATPase in the Distal Nephron Segments

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Abstract
The present study was undertaken to investigate whether or not potassium deficiency influences N-ethylmaleimide (NEM)-sensitive ATPase in the distal nephron segments of the rat. One group of animals was fed a low-K diet, whereas the normal K-group was given the same diet after supplementation with KCl. The nephron segments examined were: the medullary and cortical thick ascending limbs, the distal convoluted tubule, and the cortical, outer and inner medullary collecting ducts. NEM-sensitive ATPase activity in microdissected segments was measured by a fluorometric microassay. The plasma K+ concentration in the low-K group was 3.1 ± 0.3 mEq/l compared with 4.2 ± 0.1 mEq/1 in the normal-K group. NEM-sensitive ATPase activity in the outer medullary collecting duct of low-K diet animals was significantly greater than in normal-K animals. There was no significant difference in NEM-sensitive ATPase activity between the two groups of animals in the other nephron segments examined. It is suggested that NEM-sensitive H-ATPase activity in the outer medullary collecting duct is modulated by the potassium status of the animal.