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Imaging of Beta-Receptors in the Heart
Published in Robert J. Gropler, David K. Glover, Albert J. Sinusas, Heinrich Taegtmeyer, Cardiovascular Molecular Imaging, 2007
Jeanne M. Link, John R. Stratton, Wayne C. Levy, Jeanne Poole, James H. Caldwell
The adrenergic system plays the major role in modulation of heart rate and contractility (1). Adrenergic signaling is initiated by the binding of the adrenergic agonists, norepinephrine, and epinephrine, to adrenergic receptors. Three types of adrenergic receptors, alpha 1, alpha 2, and beta receptors, are known, and each of these has three subtypes. (β-ARs also have a fourth “putative” subtype. All the types of adrenergic receptors are found in the heart, but the ratio of β to α receptors in the heart is 10:1 (1,2) and approximately 75% to 80% of the cardiac β-AR are the β1 subtype. Binding of adrenergic agonists to the active β-AR (β1 and β2) on the outer surface of the sarcolemma causes a conformational change in the transmembrane receptor G-coupled protein that initiates a series of secondary intracellular molecular interactions. Specifically, cyclic AMP production and a number of cellular events including phosphorylation of the calcium channel and the release of calcium by the sarcoplasmic reticulum (2–4). In the healthy heart, the β-AR are part of an exquisitely balanced and complex regulatory system. While we are far from understanding all the details, in addition to contraction, the system includes myocyte growth and apoptosis (2). The β-AR are the receptors with the greatest effect on augmenting or maintaining contractility; despite the need for a maximal response from all of the available β-AR to induce the required inotropic response (1–3).
Recognition of the prioritized types and individual of pharmaceuticals and personal care products (PPCPs) in the drinking water of Shanghai and a health risk assessment
Published in Human and Ecological Risk Assessment: An International Journal, 2019
Guoqiang Gu, Haowen Yin, Qing Zhu, Lu Shen, Kun Zhang, Min Liu, Qiang Wu
Veterinary drugs may be an important component of overall pollution from PPCPs due to their heavy use in China. For example, β-adrenergic agonists (β-AAs) are primarily used to treat bronchial asthma. However, they may promote the growth of lean muscle and decrease the fat content of edible animals, a secondary use for which they have been employed since 1980, and are therefore known as “brown meat essence” in meat products in China. Therefore, typical β-AAs were selected for detection. As shown in Table 1, the maximum detection frequency was found for clorprenaline (48.6%), followed by clenbuterol (34.3%), and ractopamine (25.7%). The detection frequencies of other β-AAs were not more than 20%, which is reflective of the rate of consumption. Three generations of β-AAs have been developed and marketed to evade imposed controls. Clenbuterol, ractopamine, and clorprenaline are the representative drugs of each generation. Regulations were successively issued that prohibited the feeding or detection of clenbuterol, ractopamine, and clorprenaline in meat in 2002, 2003, and 2010, respectively (Announcement of the Ministry of Agriculture, Health, and State Food and Drug Administration 2002; Letter of animal husbandry, medicine 2003; Announcement of the Ministry of Agriculture 2010). As a result, it is not surprising that among the three, clorprenaline had the highest detection frequency and concentration in drinking water. Fortunately, the detected concentrations of β-AAs were negligible due to effective supervision, as shown in Figure 4. Even for clorprenaline, the maximum concentration was only 0.83 ng/L. Thiabendazole is also used as a veterinary drug. Compared with β-AAs, thiabendazole has low toxicity, and the maximum residue limit for the compound is 100 μg/kg in meat and milk (Announcement of the Ministry of Agriculture 2002). Its high detection frequency of 77.1% is consistent with national regulations. The detected concentrations of thiabendazole were low and ranged from 0.01 ng/L to 0.28 ng/L, as shown in Figure 4. Thiabendazole was previously found at concentrations ranging from undetectable to 10.8 ng/L in raw water in the United States (Stackelberg et al. 2004; Fram and Belitz 2011), while its concentration was less than the detection limit in drinking water (Stackelberg et al. 2004).