Parathyroid hormone (PTH) has been shown to modify Ca2+ and Na+ transport in several
epithelia. The molecular mechanisms of these effects are poorly understood. We investigated
here whether PTH may modify Na+ and K+ transport across the human red blood cell membrane
in vitro and ex vivo. Fourteen patients with severe primary or secondary hyperparathyroidism
and hypercalcemia were studied before and 5-7 days after surgical parathyroidectomy.
Erythrocyte ouabain-sensitive as well as furosemide-sensitive Na+ efflux rates of
the patients were comparable to that of healthy volunteers and remained unchanged
after parathyroidectomy. Moreover, erythrocyte Na+ fluxes of control subjects remained
unchanged when red blood cells were incubated in the presence of 1.0 IU/ml of bovine
PTH (1-85). However, erythrocytes from hyperparathyroid patients showed a significant
increase in passive K+ permeability when compared to that of healthy controls (p <
0.05). This abnormality could be corrected in vivo after parathyroidectomy and in
vitro using quinine, respectively. It is concluded that hyperparathyroidism induces
a moderate increase in Ca2+ dependent K+ permeability of erythrocytes (“Gardos effect”)
which is reversible after parathyroidectomy.
Erythrocytes
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Na and K Transport
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Parathyroid Hormone
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Hyperparathyroidism
