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Red blood cell calcium level in chronic renal failure: effect of continuous ambulatory peritoneal dialysis
Insights
Red blood cell calcium is elevated in chronic renal failure (CRF) due to impaired calcium extrusion and increased influx. Continuous ambulatory peritoneal dialysis (CAPD) does not significantly correct these red blood cell calcium abnormalities in CRF patients.
Area of Science:
- Nephrology
- Cellular Physiology
- Biochemistry
Background:
- Chronic renal failure (CRF) is associated with altered mineral metabolism.
- Red blood cell (RBC) calcium homeostasis may be disturbed in CRF.
Purpose of the Study:
- To investigate RBC calcium levels, influx, and extrusion in CRF patients.
- To evaluate the impact of continuous ambulatory peritoneal dialysis (CAPD) on these parameters.
- To explore the relationship between RBC calcium and Ca-stimulated, Mg-dependent adenosine triphosphatase (CaATPase) activity.
Main Methods:
- Measurement of RBC calcium content.
- Assessment of calcium-45 influx.
- Determination of CaATPase activity (basal and calmodulin-stimulated).
- Comparison between CRF patients, CAPD patients, and healthy controls.
Main Results:
- RBC calcium levels were significantly elevated in CRF and CAPD patients compared to controls.
- CaATPase activity, indicative of calcium extrusion, was suppressed in CRF and CAPD patients.
- Calcium influx into RBCs was increased in both CRF and CAPD groups.
- A strong inverse correlation was observed between RBC calcium and CaATPase activity in CRF patients.
- Elevated plasma vanadium levels were noted in hemodialysis and CAPD patients.
Conclusions:
- CRF leads to elevated RBC calcium primarily due to reduced calcium extrusion and increased influx.
- CAPD treatment does not effectively normalize these RBC calcium handling abnormalities.
- RBC calcium dysregulation is a significant feature of CRF, potentially exacerbated by dialysis treatments.
Abstract:
Red blood cell (RBC) calcium, calcium 45 influx, and calcium extrusion as indicated by Ca-stimulated, Mg-dependent adenosine triphosphatase (CaATPase) was determined in patients with chronic renal failure (CRF), patients with CRF receiving continuous ambulatory peritoneal dialysis (CAPD) treatment, and controls. Cell calcium, which in the controls was 5.5 mumol/L of cells, was elevated in patients with CRF--30.6 +/- 6.8 mumol/L of cells (p less than 0.002)--and in patients receiving CAPD-23.6 +/- 6.7 mumol/L of cells (p less than 0.02). Basal CaATPase activity in controls was 850.7 +/- 66.7 nmol inorganic phosphate per milligram of protein per hour. It was suppressed in patients with CRF and patients receiving CAPD: 504.9 +/- 34.4 nmol inorganic phosphate per milligram of protein per hour and 618.2 +/- 47.3 nmol inorganic phosphate per milligram of protein per hour, respectively (p less than 0.01). Calmodulin-stimulated CaATPase revealed a pattern similar to that of CaATPase basal activity. RBC calcium showed an inverse correlation with CaATPase activity (r = -0.935, p less than 0.005) in patients with CRF. Calcium influx was increased in patients with CRF and in patients receiving CAPD: 12.00 +/- 1.34 mumol/L of cells per hour and 13.60 +/- 1.70, respectively, compared with 4.61 +/- 0.39 mumol/L of cells per hour in controls (p less than 0.001). Patients with CRF have elevated RBC calcium levels mainly related to decreased extrusion and to increased influx. CAPD fails to improve substantially these abnormalities. Plasma vanadium levels were markedly elevated in patients undergoing hemodialysis and marginally in patients receiving CAPD.(ABSTRACT TRUNCATED AT 250 WORDS)