Studies on the binding of3H-dihydroalprenolol (3H-DHA) to astrocytes from cerebra of normal and hypothyroid rats show that hypothyroidism results in a decline in the β-adrenergic receptors. Ontogenic studies indicated that in normal, euthyroid rats, the maximum binding capacity (Bmax) for3H-DHA progressively increased with age while the affinity (Kd) remained unaltered. In astrocytes prepared from hypothyroid rats, total number of binding sites for3H-DHA also increased with age, however, at a given age, the number was significantly lower than that for corresponding euthyroid animals while the affinity for3H-DHA remained unaffected. Correspondingly, primary cultures of astrocytes from normal and hypothyroid brain when maintained in TH-deficient serum, display a similar reduction of3H-DHA binding. In the case of astrocytes from hypothyroid brain cultured in TH-dfficient serum, the decline can be largely restored by supplementing with normal serum. Results suggest that thyroid hormones (TH) directly or indirectly regulates the level of β-adrenergic receptors in astrocytes from developing rat brain. © 1994.
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