Effect of parathyroid hormone and uremia on erythrocyte deformability

Parathyroid hormone (PTH) caused a significant decrease in human erythrocyte filtration rate (EFR). This effect was Ca2+-dependent and was partially reversed by the Ca2+ blocker verapamil. It was mimicked by the Ca2+ ionophore A-23187. Mg2+ even at high concentrations could not substitute for Ca2+. There was a dose response between the filtration rate and Ca2+ or PTH concentrations. Serum ultrafiltrate of patients with chronic renal failure and secondary hyperparathyroidism caused significant inhibition similar to that seen with PTH extract. Ultrafiltrate from patients with chronic renal failure following parathyroidectomy and from healthy individuals did not cause this phenomenon. Erythroyctes deformability in uremic patients appears to be caused by high PTH levels. Our present findings agree with ones about the toxic effects of PTH on various biological systems.