Analysis of molecular mechanism on the training effects using adrenergic receptor agonists

在这项研究中，我们试图研究纵向抑制生长的影响，克伦特罗（β-2肾上腺素能受体激动剂）使用逆转录聚合酶链反应（RT-PCR）分析的培养破骨细胞来自小鼠骨髓细胞与骨化三醇（10 nM）和地塞米松（10 nM）。在前破骨细胞向成熟破骨细胞分化的过程中，给予克伦特罗。克伦特罗增加破骨细胞的数量。妥洛特罗和异丙肾上腺素也能增加破骨细胞。但选择性β 2受体拮抗剂丁恶胺和蛋白激酶A抑制剂H89可抑制破骨细胞的增加。提示破骨细胞的增加可能是由cAMP的增加引起的，而PGE_2促进破骨细胞的形成是众所周知的。PGE 2合成酶考克斯-2的mRNA表达也随着克伦特罗、妥布特罗和异丙肾上腺素的处理而增加。克伦特罗还能增加骨吸收细胞因子IL-1β和IL-6的mRNA表达，从而通过激活成骨细胞促进骨形成。结果表明，盐酸克伦特罗对破骨细胞形成系统的影响较强，而对成骨细胞的影响较小。这意味着这些药物对各种细胞都有激活作用，但整体效果是复杂的。我们证实，克伦特罗可增加UCP 3和MyoD mRNA的表达，UCP 3可促进脂肪分解，MyoD是核调节因子。他们认为，克伦特罗增加MyoD作为生肌的主调节剂，并可能诱导肌肉肥大和从慢肌到快肌的转变。

In this study, we tried to examine the longitudinal inhibitory growth effects on bone of clenbuterol (beta-2 adrenergic receptor agonist) using reverse-transcription polymerase chain reaction (RT-PCR) analysis of the cultured osteoclast cells derived from mouse bone marrow cells with calcitriol (10 nM)and dexamethasone (10 nM). During the differentiation process from preosteoclasts into the matured osteoclasts, the clenbuterol were administered into the culture system. Clenbuterol increased the number of osteoclasts. The both of tulobuterol and isoproterenol also increased the osteoclasts. But the selective beta-2 antagonist (butoxamine) and H89 (protein kinase A inhibitor) inhibited the increased osteoclasts. It suggested the increased osteoclasts might be induced by the increased cAMP.It is well known that the PGE2 accelerate the forming of osteoclasts. The mRNA expression of COX-2 which is PGE2 synthetase also increased with the treatments of clenbuterol, turobuterol, and isoproterenol. Furthermore, the mRNA expression of bone resorptive cytokines, IL-1β and IL-6 were increased by clenbuterol, which also accelerated the bone forming by the osteoblasts activation... These results suggested that this clenbuterol affected more strongly on osteoclast forming system but a little on osteoblast. It means that these drugs have the activating action on various cells but the whole effects are complicated. Therefore, the using of these drugs should be careful.We confirmed that clenbuterol increased the expression of mRNAs of UCP3 which increases lipolysis and MyoD which is nuclear regulatory factor. They suggested that clenbuterol increased the MyoD as the myogenic master regulator and might induce the muscle hypertrophy and the transformation from slow-to fast-twitch muscle.