IN T RODUC T ION Beta-agonists, or β2-adrenergic agonists are, often used as drugs to treat asthma and other pulmonary diseases. They act on the β2-adrenergic receptor and cause smooth muscle relaxation, resulting in the dilation of bronchial passages and other effects. However, some beta agonists have been used illegally in meat husbandry, since they can also promote muscle growth instead of f...

beta-Adrenergic receptor downregulation is the end result of cellular adaptation to prolonged agonist exposure. The factors mediating receptor downregulation include receptor phosphorylation, receptor movement from the plasma membrane to intracellular sites, and alterations in nascent receptor synthesis. We have previously demonstrated a downregulation of the left ventricular beta-receptor duri...

Prolonged exposure of cells or tissues to drugs or hormones such as catecholamines leads to a state of refractoriness to further stimulation by that agent, known as homologous desensitization. In the case of the beta-adrenergic receptor coupled to adenylate cyclase, this process has been shown to be intimately associated with the sequestration of the receptors from the cell surface through a cA...

The beta(3)-adrenoreceptor plays a major role in lipolysis but the role and distribution of beta(3)-receptors in other specific sites have not been extensively studied. beta(3)-adrenergic receptors are present not only in adipose tissue but also in human gall bladder, colon, prostate, and skeletal muscle. Recently, beta(3)-adrenergic receptor stimulation was shown to elicit vasorelaxation of ra...

Changes in the beta-adrenergic receptor-G protein-adenylate cyclase complex were investigated in an experimental canine model of low-output heart failure produced by chronic rapid ventricular pacing. The contractile response occurring after exposure to the beta-adrenergic agonist dobutamine, measured as peak left ventricular + dP/dt, was decreased after 3 weeks of pacing. To further characteriz...

In normal thyroid cells, the TSH-adenylate cyclase system plays a pivotal role in controlling growth and differentiation. However, the role of this system in the growth of thyroid carcinoma is not well understood. To investigate this subject, we have established four new human thyroid carcinoma cell lines, designated BHP 2-7, 7-13, 10-3, and 18-21, from different patients. Northern gel analysis...

BACKGROUND During both cardiac maturation and myopathy, elevated levels of circulating catecholamines coincide with alterations in impulse propagation. An in vitro model of cultured cardiomyocytes was used to study the effects of adrenergic stimulation on the conduction characteristics of immature heart cells. METHODS AND RESULTS Neonatal rat cardiomyocytes were cultured on preparations desig...