Institute of Pharmacology, Pharmacy and Toxicology, Faculty of Veterinary Medicine, University of Leipzig, D-04103 Leipzig, Germany.
Clinic for Birds and Reptiles, Faculty of Veterinary Medicine, University of Leipzig, D-04103 Leipzig, Germany.
Poult Sci. 2018 Mar 1;97(3):1041-1049. doi: 10.3382/ps/pex362.
In conventional meat-type (British United Turkey (B.U.T.) Big 6) turkey hearts, it has been shown that all cardiac chambers exhibit down-regulation of the β1-adrenoceptors (β1-AR) and concomitantly cAMP accumulation with increasing age regardless of sex. In this study we proved the hypothesis that breed differences exist in age-dependent alterations in the β1-AR system. Right (RA) and left (LA) atrial as well as right (RV) and left (LV) ventricular tissues were collected from male and female Cröllwitzer "wild-type" turkey poults of increasing age (6 wk, 12 wk, 16 wk, 21 wk). The β1-AR density and function were quantified by (-)-[125I]-iodocyanopindolol (ICYP) radioligand binding analysis in cell membranes from 4 cardiac chambers. Basal and stimulated cAMP production was determined as indicator of the receptor function. Wild-type turkeys showed significantly higher heart to body weight ratio than the meat-type B.U.T. Big 6 turkeys. In both sexes of Cröllwitzer turkey hearts, the β1-AR density decreased with age but significance was reached in male cardiac chambers. The receptor affinity (KD) and subtype distribution were not altered. Sex had no effect on age-related decrease in receptor density but had an effect on adenylate cyclase (AC) activity and subsequently cAMP production. In male Cröllwitzer turkey hearts of all ages, cAMP remained at same level, whereas this was even increased in female cardiac chambers. Thus, breed affected age-related receptor-, G-protein and AC-stimulated cAMP formation in normal ventricles and atria, with females exhibiting pronounced increase with age. This suggests that the receptor signaling in wild-type turkey hearts is not as blunted as in hearts of meat-type turkey poults in which stressful farming conditions and fast growing lead to receptor down-regulation.
在传统的肉用型（英国联合火鸡（B.U.T.）Big 6）火鸡心脏中，已经表明所有的心脏腔室都表现出β1-肾上腺素能受体（β1-AR）的下调，并且随着年龄的增长，cAMP 积累增加，而与性别无关。在这项研究中，我们证明了这样一个假设，即在依赖于年龄的β1-AR 系统改变方面存在品种差异。从雄性和雌性 Cröllwitzer“野生型”火鸡雏鸡中收集右心房（RA）和左心房（LA）以及右心室（RV）和左心室（LV）组织，年龄逐渐增加（6 周、12 周、16 周、21 周）。通过细胞膜中（-）-[125I]-碘氰基苯并吲哚（ICYP）放射性配体结合分析来定量β1-AR 密度和功能。作为受体功能的指标，测定基础和刺激的 cAMP 产生。野生型火鸡的心脏重量与体重比明显高于肉用型 B.U.T. Big 6 火鸡。在 Cröllwitzer 火鸡心脏的两种性别中，β1-AR 密度随年龄而降低，但在雄性心脏腔室中达到显著性。受体亲和力（KD）和亚型分布没有改变。性别对与年龄相关的受体密度降低没有影响，但对腺苷酸环化酶（AC）活性和随后的 cAMP 产生有影响。在所有年龄的雄性 Cröllwitzer 火鸡心脏中，cAMP 保持在相同水平，而在雌性心脏腔室中甚至增加。因此，品种影响正常心室和心房中与年龄相关的受体、G 蛋白和 AC 刺激的 cAMP 形成，而雌性随着年龄的增长表现出明显的增加。这表明，与肉用型火鸡雏鸡的心脏相比，野生型火鸡心脏的受体信号传导并没有那么迟钝，在肉用型火鸡雏鸡中，应激性的饲养条件和快速生长导致了受体下调。
