OUABAIN-BINDING SITES OF RETICULOCYTES FROM GUINEA-PIGS TREATED WITH TRIIODOTHYRONINE

To understand the mechanism of reduced number of sodium pump units (ouabain-binding sites, OBS) of erythrocytes in hyperthyroidism, OBS of reticulocytes from guinea pigs injected with triiodothyronine (T3) were measured. Reticulocytosis was induced in 16 guinea pigs by withdrawing 6 to 10 mL of blood for 5 days followed by 2 days rest. T3 ( 50 μg 100 g body weight) was injected into seven animals on days 4 and 6, and the remainder were injected with solvent for T3. Reticulocyte-rich blood was withdrawn on day 8. Oxygen consumption determined 24 hours after the first injection of T3 was 30% higher in the T3-treated animals (P < .001). OBS of reticulocytes from control animals were sixfold higher than that of mature erythrocytes. Reticulocytes from T3-treated guinea pigs had significantly lower OBS (P < .01) compared with controls. We conclude that the loss of OBS induced by thyroid hormones probably occurs during the formation of reticulocytes. © 1991.