Role of glomerular prostanoid in control of glomerular filtration rate in rats

The role of cystatin C (Cys-C) as a marker of glomerular filtration rate (GFR) in pregnancy is undetermined. Measurements of Cys-C and creatinine (Cr) were taken at 14–17+6, 18–23+6, 27–31+6 weeks' gestation, at delivery and 2–6 weeks postpartum in a prospective observational study of 27 women. There was no difference between Cys-C levels in early and late second trimester, but they were significantly higher in early third trimester ( P < 0.001) than second trimester, despite no concurrent increase in Cr. Cys-C was also significantly higher at delivery than at all other times in pregnancy ( P < 0.001) and fell to postpartum values higher than second trimester measurements ( P < 0.01), but lower than delivery ( P<0.001). In conclusion, changes in Cys-C may be influenced by pregnancy-related changes in glomerular filtration and therefore we would advise against their use as a marker of GFR in pregnancy.

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Increased tubuloglomerular feedback activity in Milan hypertensive rats

AJP Renal Physiology ◽

10.1152/ajprenal.1986.250.6.f967 ◽

1986 ◽

Vol 250 (6) ◽

pp. F967-F974 ◽

Cited By ~ 5

Author(s):

U. Boberg ◽

A. E. Persson

Keyword(s):

Glomerular Filtration Rate ◽

Glomerular Filtration ◽

Filtration Rate ◽

Tubuloglomerular Feedback ◽

Spontaneously Hypertensive ◽

Arterial Blood ◽

Single Nephron ◽

Flow Pressure ◽

Normotensive Strain

Studies of whole-kidney function and micropuncture measurements in superficial nephrons were performed to investigate the role of the tubuloglomerular feedback (TGF) in the excretion of salt and water in hydropenic and volume-expanded rats of the spontaneously hypertensive Milan strain (MHS). The rats were 3.5-5 and 5-7 wk old, and age-matched animals from the Milan normotensive strain (MNS) served as controls. There was no difference in mean arterial blood pressure (Pa) between the 3.5- to 5-wk-old prehypertensive MHS (MHSp) and MNS rats, but the glomerular filtration rate (GFR) was higher in MHSp than in MNS [1.35 vs. 0.80 ml X min-1 X g kidney wt (KW)-1, P less than 0.01]. The distal single-nephron glomerular filtration rate (SNGFR) was also higher in MHSp than in MNS (28.6 vs. 20.2 nl X min-1 X g KW-1, P less than 0.05). TGF was determined from both stop-flow pressure response and proximal and distal SNGFR. It was found that MHSp exhibited essentially no TGF response. During development of hypertension 5- to 7-wk-old MHS (MHSd) had a higher Pa than MNS (120 vs. 98 mmHg, P less than 0.01). Normally GFR and SNGFR increase with age, and such was the case with MNS (0.8 to 1.02 ml X min-1 X g KW-1 and 20.2 to 23.4 nl X min-1 X g KW-1), but in MHSd there was a decrease in both GFR and SNGFR with age (1.35 to 1.10 ml X min-1 X g KW-1 and 28.3 to 18.3 nl X min-1 X g KW-1).(ABSTRACT TRUNCATED AT 250 WORDS)

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The potential role of the eGFR in differentiating between true and pseudohyperkalaemia

Annals of Clinical Biochemistry International Journal of Laboratory Medicine ◽

10.1177/0004563220966858 ◽

2020 ◽

Vol 57 (6) ◽

pp. 444-455

Author(s):

Thomas G Morris ◽

Sushmita Lamba ◽

Thomas Fitzgerald ◽

Gary Roulston ◽

Helen Johnstone ◽

...

Keyword(s):

Renal Function ◽

Glomerular Filtration Rate ◽

Glomerular Filtration ◽

Filtration Rate ◽

Blood Count ◽

Potential Role ◽

Estimated Glomerular Filtration Rate ◽

Full Blood Count ◽

Cut Points

Background Differentiating between true and pseudohyperkalaemia is essential for patient management. The common causes of pseudohyperkalaemia include haemolysis, blood cell dyscrasias and EDTA contamination. One approach to differentiate between them is by checking the renal function, as it is believed that true hyperkalaemia is rare with normal function. This is logical, but there is limited published evidence to support it. The aim of this study was to investigate the potential role of the estimated glomerular filtration rate in differentiating true from pseudohyperkalaemia. Methods GP serum potassium results >6.0 mmol/L from 1 January 2017 to 31 December 2017, with a repeat within seven days, were included. Entries were retrospectively classified as true or pseudohyperkalaemia based on the potassium reference change value and reference interval. If the initial sample had a full blood count, it was classified as normal/abnormal to remove blood cell dyscrasias. Different estimated glomerular filtration rate cut-points were used to determine the potential in differentiating true from pseudohyperkalaemia. Results A total of 272 patients were included with potassium results >6.0 mmol/L, with 145 classified as pseudohyperkalaemia. At an estimated glomerular filtration rate of 90 ml/min/1.73 m2, the negative predictive value was 81% (95% CI: 67–90%); this increased to 86% (95% CI: 66–95%) by removing patients with abnormal full blood counts. When only patients with an initial potassium ≥6.5 mmol/L were included (regardless of full blood count), at an estimated glomerular filtration rate of 90 ml/min/1.73 m2, the negative predictive value was 100%. Lower negative predictive values were seen with decreasing estimated glomerular filtration rate cut-points. Conclusion Normal renal function was not associated with true hyperkalaemia, making the estimated glomerular filtration rate a useful tool in predicting true from pseudohyperkalaemia, especially for potassium results ≥6.5 mmol/L.

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