Tong Wang, Tommy Liu, Shuhua Xu, Gustavo Frindt, Alan M Weinstein, Lawrence G Palmer
{"title":"膳食中摄入大量 K+ 会抑制近端肾小管的转运。","authors":"Tong Wang, Tommy Liu, Shuhua Xu, Gustavo Frindt, Alan M Weinstein, Lawrence G Palmer","doi":"10.1152/ajprenal.00013.2023","DOIUrl":null,"url":null,"abstract":"<p><p>The impact of chronic dietary K<sup>+</sup> loading on proximal tubule (PT) function was measured using free-flow micropuncture along with measurements of overall kidney function, including urine volume, glomerular filtration rate, and absolute and fractional Na<sup>+</sup> and K<sup>+</sup> excretion in the rat. Feeding animals a diet with 5% KCl [high K<sup>+</sup> (HK)] for 7 days reduced glomerular filtration rate by 29%, increased urine volume by 77%, and increased absolute K<sup>+</sup> excretion by 202% compared with rats on a 1% KCl [control K<sup>+</sup> (CK)] diet. HK did not change absolute Na<sup>+</sup> excretion but significantly increased fraction excretion of Na<sup>+</sup> (1.40% vs. 0.64%), indicating that fractional Na<sup>+</sup> absorption is reduced by HK. PT reabsorption was assessed using free-flow micropuncture in anesthetized animals. At 80% of the accessible length of the PT, measurements of inulin concentration indicated volume reabsorption of 73% and 54% in CK and HK, respectively. At the same site, fractional PT Na<sup>+</sup> reabsorption was 66% in CK animals and 37% in HK animals. Fractional PT K<sup>+</sup> reabsorption was 66% in CK and 37% in HK. To assess the role of Na<sup>+</sup>/H<sup>+</sup> exchanger isoform 3 (NHE3) in mediating these changes, we measured NHE3 protein expression in total kidney microsomes as well as surface membranes using Western blots. We found no significant changes in protein in either cell fraction. Expression of the Ser<sup>552</sup> phosphorylated form of NHE3 was also similar in CK and HK animals. Reduction in PT transport may facilitate K<sup>+</sup> excretion and help balance Na<sup>+</sup> excretion by shifting Na<sup>+</sup> reabsorption from K<sup>+</sup>-reabsorbing to K<sup>+</sup>-secreting nephron segments.<b>NEW & NOTEWORTHY</b> In rats fed a diet rich in K<sup>+</sup>, proximal tubules reabsorbed less fluid, Na<sup>+</sup>, and K<sup>+</sup> compared with those in animals on a control diet. Glomerular filtration rates also decreased, probably due to glomerulotubular feedback. These reductions may help to maintain balance of the two ions simultaneously by shifting Na<sup>+</sup> reabsorption to K<sup>+</sup>-secreting nephron segments.</p>","PeriodicalId":7588,"journal":{"name":"American Journal of Physiology-renal Physiology","volume":null,"pages":null},"PeriodicalIF":3.7000,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10396284/pdf/","citationCount":"0","resultStr":"{\"title\":\"High dietary K<sup>+</sup> intake inhibits proximal tubule transport.\",\"authors\":\"Tong Wang, Tommy Liu, Shuhua Xu, Gustavo Frindt, Alan M Weinstein, Lawrence G Palmer\",\"doi\":\"10.1152/ajprenal.00013.2023\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p><p>The impact of chronic dietary K<sup>+</sup> loading on proximal tubule (PT) function was measured using free-flow micropuncture along with measurements of overall kidney function, including urine volume, glomerular filtration rate, and absolute and fractional Na<sup>+</sup> and K<sup>+</sup> excretion in the rat. Feeding animals a diet with 5% KCl [high K<sup>+</sup> (HK)] for 7 days reduced glomerular filtration rate by 29%, increased urine volume by 77%, and increased absolute K<sup>+</sup> excretion by 202% compared with rats on a 1% KCl [control K<sup>+</sup> (CK)] diet. HK did not change absolute Na<sup>+</sup> excretion but significantly increased fraction excretion of Na<sup>+</sup> (1.40% vs. 0.64%), indicating that fractional Na<sup>+</sup> absorption is reduced by HK. PT reabsorption was assessed using free-flow micropuncture in anesthetized animals. At 80% of the accessible length of the PT, measurements of inulin concentration indicated volume reabsorption of 73% and 54% in CK and HK, respectively. At the same site, fractional PT Na<sup>+</sup> reabsorption was 66% in CK animals and 37% in HK animals. Fractional PT K<sup>+</sup> reabsorption was 66% in CK and 37% in HK. To assess the role of Na<sup>+</sup>/H<sup>+</sup> exchanger isoform 3 (NHE3) in mediating these changes, we measured NHE3 protein expression in total kidney microsomes as well as surface membranes using Western blots. We found no significant changes in protein in either cell fraction. Expression of the Ser<sup>552</sup> phosphorylated form of NHE3 was also similar in CK and HK animals. Reduction in PT transport may facilitate K<sup>+</sup> excretion and help balance Na<sup>+</sup> excretion by shifting Na<sup>+</sup> reabsorption from K<sup>+</sup>-reabsorbing to K<sup>+</sup>-secreting nephron segments.<b>NEW & NOTEWORTHY</b> In rats fed a diet rich in K<sup>+</sup>, proximal tubules reabsorbed less fluid, Na<sup>+</sup>, and K<sup>+</sup> compared with those in animals on a control diet. Glomerular filtration rates also decreased, probably due to glomerulotubular feedback. These reductions may help to maintain balance of the two ions simultaneously by shifting Na<sup>+</sup> reabsorption to K<sup>+</sup>-secreting nephron segments.</p>\",\"PeriodicalId\":7588,\"journal\":{\"name\":\"American Journal of Physiology-renal Physiology\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":3.7000,\"publicationDate\":\"2023-08-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10396284/pdf/\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"American Journal of Physiology-renal Physiology\",\"FirstCategoryId\":\"3\",\"ListUrlMain\":\"https://doi.org/10.1152/ajprenal.00013.2023\",\"RegionNum\":2,\"RegionCategory\":\"医学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"2023/6/15 0:00:00\",\"PubModel\":\"Epub\",\"JCR\":\"Q1\",\"JCRName\":\"PHYSIOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"American Journal of Physiology-renal Physiology","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1152/ajprenal.00013.2023","RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2023/6/15 0:00:00","PubModel":"Epub","JCR":"Q1","JCRName":"PHYSIOLOGY","Score":null,"Total":0}
High dietary K+ intake inhibits proximal tubule transport.
The impact of chronic dietary K+ loading on proximal tubule (PT) function was measured using free-flow micropuncture along with measurements of overall kidney function, including urine volume, glomerular filtration rate, and absolute and fractional Na+ and K+ excretion in the rat. Feeding animals a diet with 5% KCl [high K+ (HK)] for 7 days reduced glomerular filtration rate by 29%, increased urine volume by 77%, and increased absolute K+ excretion by 202% compared with rats on a 1% KCl [control K+ (CK)] diet. HK did not change absolute Na+ excretion but significantly increased fraction excretion of Na+ (1.40% vs. 0.64%), indicating that fractional Na+ absorption is reduced by HK. PT reabsorption was assessed using free-flow micropuncture in anesthetized animals. At 80% of the accessible length of the PT, measurements of inulin concentration indicated volume reabsorption of 73% and 54% in CK and HK, respectively. At the same site, fractional PT Na+ reabsorption was 66% in CK animals and 37% in HK animals. Fractional PT K+ reabsorption was 66% in CK and 37% in HK. To assess the role of Na+/H+ exchanger isoform 3 (NHE3) in mediating these changes, we measured NHE3 protein expression in total kidney microsomes as well as surface membranes using Western blots. We found no significant changes in protein in either cell fraction. Expression of the Ser552 phosphorylated form of NHE3 was also similar in CK and HK animals. Reduction in PT transport may facilitate K+ excretion and help balance Na+ excretion by shifting Na+ reabsorption from K+-reabsorbing to K+-secreting nephron segments.NEW & NOTEWORTHY In rats fed a diet rich in K+, proximal tubules reabsorbed less fluid, Na+, and K+ compared with those in animals on a control diet. Glomerular filtration rates also decreased, probably due to glomerulotubular feedback. These reductions may help to maintain balance of the two ions simultaneously by shifting Na+ reabsorption to K+-secreting nephron segments.
期刊介绍:
The American Journal of Physiology - Renal Physiology publishes original manuscripts on timely topics in both basic science and clinical research. Published articles address a broad range of subjects relating to the kidney and urinary tract, and may involve human or animal models, individual cell types, and isolated membrane systems. Also covered are the pathophysiological basis of renal disease processes, regulation of body fluids, and clinical research that provides mechanistic insights. Studies of renal function may be conducted using a wide range of approaches, such as biochemistry, immunology, genetics, mathematical modeling, molecular biology, as well as physiological and clinical methodologies.