Abstract
We have previously shown that erythrocytes from hyperthyroid turkeys are identical to normal turkey erythrocytes with respect to the number and affinity of β-receptors, maximal catecholamine-stimulatable adenylate cyclase activity, and cAMP accumulation. In the present study we now report that despite these similarities, the physiological responsiveness of hyperthyroid cells to catecholamines is markedly altered. Maximal catecholamine-induced stimulation of potassium ion transport in erythrocytes from hyperthyroid turkeys is significantly reduced (21.8 ± 2.4 vs. 34.1 ± 3.0 meq/liter cells-h; P < 0.005). In addition, there is a slight increase in the concentration of isoproterenol required for the induction of half-maximal stimulation (5.7 ± 0.8 vs. 3.9 ± 0.4 nM; P < 0.05). Quantitative assessment of potassium influx in relation to β-receptor occupancy by agonist indicates that despite the absence of any change in β-receptor number, the degree of stimulation of potassium transport per agonist-occupied β-re...
Published Version
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