Altered plasma catecholamines and numbers of α- and β-adrenergic receptors in platelets and leucocytes in hyperthyroid patients normalized under antithyroid treatment

Abstract

We measured plasma catecholamines, alpha- and beta-adrenoreceptor numbers and the accumulation of cyclic adenosine monophosphate (cAMP) in the unstimulated state and in response to 10 mumol/l (-) isoproterenol in blood cells from 29 euthyroid controls and from 18 patients with spontaneous hyperthyroidism. In the thyrotoxic patients plasma norepinephrine (1.14 +/- 0.5 nmol/l) and epinephrine (0.3 +/- 0.14 nmol/l) were significantly decreased compared with plasma norepinephrine (1.87 +/- 0.7 nmol) and epinephrine (0.41 +/- 0.19 nmol/l) in the controls (P less than 0.01 and P less than 0.05, respectively) and the values obtained in subjects rendered euthyroid by antithyroid treatment (P less than 0.001, respectively). alpha-adrenoceptor density in platelet membranes obtained from patients in the hyperthyroid state (114 +/- 38 sites per cell) was significantly decreased when compared with controls (159 +/- 48 sites per cell, P less than 0.01) and the values from patients under effective antithyroid treatment (136 +/- 35 sites per cell, P less than 0.01). On the contrary, a significant increase in beta-adrenoceptor density in mononuclear leucocyte (MNL) membranes was found in hyperthyroid patients (1751 +/- 237 sites/cell) when compared with controls (1510 +/- 351 sites/cell, P less than 0.05) and the same patients following antithyroid treatment (1455 +/- 260 sites/cell, P less than 0.001). The equilibrium dissociation constants (KD) did not change in hyperthyroidism. Basal cAMP concentrations in MNL were higher in untreated thyrotoxicosis (45 +/- 18 pmol/10(6) cells/10 min) than in patients in the euthyroid state (35 +/- 9 pmol/10(6) cells/10 min, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)