Effect of parathyroid hormone on the fragility and enzyme activities of red blood cells from young and mature rabbits.

The effect of parathyroid hormone on erythrocytes from newborn and adult rabbits was studied in relation to the fragility pattern in hypotonic salt solutions and the activities of Ca- and Mg-dependent ATPases. Median osmotic fragility of red blood cells from newborn rabbits was significantly higher than in red blood cells from mature rabbits. Parathyroid hormone increased the mean osmotic fragility of red blood cells from newborn and adult rabbits, but showed the greater effect on those from newborns. Similarly, the hormone stimulated to a much greater extent the Ca-ATPase, but not the Mg-ATPase in red blood cells from the newborn rabbits, in comparison with red blood cells from adult rabbits. Parathyroid hormone, which is greatly elevated in the blood of patients with chronic renal failure, may be one cause for the anaemia seen in these patients, and its effect, which is mediated by Ca-ATPase activity, is stronger on young red blood cells. Significant morphological changes in the young red blood cells, observed by scanning electron microscopy, were caused by parathyroid hormone.