The Paradox of Renal Bicarbonate Reabsorption

Physiology ◽  
1990 ◽  
Vol 5 (1) ◽  
pp. 13-17
Author(s):  
F Kiil
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Bicarbonate Reabsorption ◽  
Main Determinants

A time-honored paradox of renal bicarbonate reabsorption can be understood by realizing that filtered bicarbonate rather than glomerular filtration rate and plasma pH rather than PCO2 are the main determinants of bicarbonate reabsorption.

MO652EFFECT OF ESTIMATED GLOMERULAR FILTRATION RATE (EGFR) ON  HEMOGLOBIN CHANGE INDUCED BY SODIUM-GLUCOSE COTRANSPORTER 2  INHIBITORS (SGLT2I)

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
Alba Maroto ◽  
Ester Domenech ◽  
Maria Marques Vidas ◽  
Paula López ◽  
Jose' M Portoles
Keyword(s):  
Chronic Kidney Disease ◽  
Renal Function ◽  
Multivariate Analysis ◽  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Estimated Glomerular Filtration Rate ◽  
Sglt2 Inhibitors ◽  
Sodium Glucose Cotransporter ◽  
Main Determinants

Abstract Background and Aims The use of sodium-glucose cotransporter 2 inhibitors (SGLT2i) is associated with increase of hemoglobin (Hb) levels and this effect has been related to improvement of tubulointerstitial hypoxia and increase on EPO production. Chronic kidney disease (CKD) associated anemia is mainly due to decreased EPO synthesis. The aim of this study was to assess if the degree of Hb increase induced by SGLT2i is higher on T2DM patients with decreased estimated glomerular filtration rate (eGFR). Method We analyzed the changes on Hb after 12 months of SGLT2i treatment in T2DM patients with different degrees of eGFR. All patients were on maximum tolerated RAA system blockade, and none was on erythropoiesis or iron therapy. Results 62 patients were include, age 67,6 ± 12,3 years, 72.6% males, eGFR CKD EPI 62,9 ± 21 (21-108) ml/min/1.73m2. Type of SGLT2i was dapagliflozin (46.8%), canagliflozin (30,5%) and empagliflozin (22,6%). 7 patients discontinued SGLT2i therapy and 62 were finally include in the analysis. Treatment with SGLT2i induced increase of Hb levels ( ΛHb 0,57 mg/dl SE 0,17 95% CI 0,25-0,93, p 0,001) independently of eGFR (aR2 0.02 p ns) In the multivariate analysis, initial eGFR, and basal Hb were the main determinants of the Hb increase induced by SGLT2i treatment (aR2 0,29). eGFR (≤60 vs >60 ml/min/173) or type of SGLT2i did not modified ΛHb Conclusion We conclude that SGLT2 inhibitors induce increase on Hb level independently of eGFR, in patients with preserved renal function, by mechanisms that are yet to be determined.

scholarly journals Tubule-vascular feedback in renal autoregulation

2019 ◽  
Vol 316 (6) ◽  
pp. F1218-F1226 ◽  
Author(s):  
Cesar A. Romero ◽  
Oscar A. Carretero
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Distal Tubule ◽  
Thick Ascending Limb ◽  
Molecular Signaling ◽  
Feedback Mechanisms ◽  
Salt Diet ◽  
Connecting Tubule ◽  
Main Determinants

Afferent arteriole (Af-Art) diameter regulates pressure and flow into the glomerulus, which are the main determinants of the glomerular filtration rate. Thus, Af-Art resistance is crucial for Na+ filtration. Af-Arts play a role as integrative centers, where systemic and local systems interact to determine the final degree of resistance. The tubule of a single nephron contacts an Af-Art of the same nephron at two locations: in the transition of the thick ascending limb to the distal tubule (macula densa) and again in the connecting tubule. These two sites are the anatomic basis of two intrinsic feedback mechanisms: tubule-glomerular feedback and connecting tubule-glomerular feedback. The cross communications between the tubules and Af-Arts integrate tubular Na+ and water processing with the hemodynamic conditions of the kidneys. Tubule-glomerular feedback provides negative feedback that tends to avoid salt loss, and connecting tubule-glomerular feedback provides positive feedback that favors salt excretion by modulating tubule-glomerular feedback (resetting it) and increasing glomerular filtration rate. These feedback mechanisms are also exposed to systemic modulators (hormones and the nervous system); however, they can work in isolated kidneys or nephrons. The exaggerated activation or absence of any of these mechanisms may lead to disequilibrium in salt and water homeostasis, especially in extreme conditions (e.g., high-salt diet/low-salt diet) and may be part of the pathogenesis of some diseases. In this review, we focus on molecular signaling, feedback interactions, and the physiological roles of these two feedback mechanisms.

Clinical Renal Function Testing by External Double Isotope Monitoring Technique

1971 ◽  
Vol 10 (01) ◽  
pp. 16-24
Author(s):  
J. Fog Pedersen ◽  
M. Fog Pedersen ◽  
Paul Madsen
Keyword(s):  
Renal Function ◽  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Plasma Flow ◽  
Filtration Rate ◽  
Renal Plasma Flow ◽  
Correlation Coefficients ◽  
Feedback System ◽  
Effective Renal Plasma Flow ◽  
Advantages And Disadvantages

SummaryAn accurate catheter-free technique for clinical determination simultaneouslyof glomerular filtration rate and effective renal plasma flow by means of radioisotopes has been developed. The renal function is estimated by the amount of radioisotopes necessary to maintain a constant concentration in the patient’s blood. The infusion pumps are steered by a feedback system, the pumps being automatically turned on when the radiation measured over the patient’s head falls below a certain preset level and turned off when this level is again readied. 131I-iodopyracet was used for the estimation of effective renal plasma flow and125I-iothalamate estimation of the glomerular filtration rate. These clearances were compared to the conventional bladder clearances and good correlation was found between these two clearance methods (correlation coefficients 0.97 and.90 respectively). The advantages and disadvantages of this new clearance technique are discussed.

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