تأثیر تغذیه متوالی و متناوب بتاآگونیست زیلپاترول هیدروکلراید روی بیان ژن گیرنده های بتاآدرنرژیک ماهیچه در بره های نر پرواری

نوع مقاله : علمی پژوهشی- فیزیولوژی

نویسندگان

1 عضو هیأت علمی گروه علوم دامی، دانشکده کشاورزی و منابع طبیعی مغان، دانشگاه محقق اردبیلی

2 استادیار گروه علوم دامی، پردیس کشاورزی و منابع طبیعی کرج، دانشگاه تهران

3 دانشگاه محقق اردبیلی

4 پردیس کشاورزی و منابع طبیعی کرج، دانشگاه تهران

5 دانشکده علوم دامی و شیلات، دانشگاه علوم کشاورزی و منابع طبیعی ساری

چکیده

هدف از این آزمایش ارزیابی اثرات سه روش مختلف مصرف زیلپاترول هیدروکلراید به مدت 42 روز آخر دوره پرواربندی روی بیان ژن گیرنده های 1β و 2β آدرنرژیک در بره های نر پرواری لری-بختیاری بود. تغذیه متوالی زیلپاترول (روزانه)، تغذیه متناوب و به صورت یک روز در میان (1on 1 off) و تغذیه متناوب و به صورت دو روز مصرف و دو روز استراحت (2on 2off) به عنوان روش های مختلف تغذیه به کار برده شدند. تعداد 32 راس بره نر با میانگین وزن اولیه 7/4± 44 کیلوگرم براساس وزن اولیه به 4 گروه (8n=) تقسیم و تا آخر دوره پرواربندی با جیره حاوی 14 درصد پروتئین و 2/0 میلی گرم زیلپاترول به ازای هر کیلوگرم وزن زنده بره ها تغذیه شدند. جیره پایه بدون زیلپاترول به عنوان گروه شاهد در نظر گرفته شد. به منظور تعیین بیان ژن گیرنده های بتاآدرنرژیک، سه مرحله نمونه گیری به روش بیوپسی از ماهیچه ران از 3 راس بره در هر تیمار در روزهای صفر، 21 و 42 آزمایش انجام شد و نمونه ها بلافاصله در نیتروژن مایع قرار داده شدند. در آزمایشگاه پس از استخراج RNA کل از بافت ماهیچه، cDNA با استفاده از آنزیم رونوشت بردار معکوس سنتز شد. پس از طراحی آغازگرها، RT-PCR برای نمونه های cDNA ، با استفاده از دستگاه iQ5 BioRad انجام شد. نتایج این تحقیق نشان داد که اثرات اصلی و اثر متقابل مدت زمان مصرف و روش مصرف زیلپاترول روی بیان نسبی ژن گیرنده1 β و2β آدرنرژیک معنی دار نبود. همچنین در مقایسه تیمارها با گروه شاهد نیز تفاوت معنی داری در سطح 05/0 مشاهده نشد. بنابراین تغذیه متناوب زیلپاترول هیدروکلراید بیان ژن گیرنده های بتاآدرنرژیک را تحت تأثیر قرار نداد.

کلیدواژه‌ها


عنوان مقاله [English]

The Effects of Continuous and Intermittent Feeding of β-agonist Zilpaterol Hydrochloride on Muscle β-adrenergic Receptors Gene Expression in Feedlot Male Lambs

نویسندگان [English]

  • Vahid Vahedi 1
  • Mostafa sadeghi 2
  • Nemat Hedayat evrigh 3
  • Mohammad Javad Najafpanah 4
  • Essa Dirandeh 5
1 Moghan College of Agriculture and Natural Resources, University of Mohaghegh Ardabili
2 Department of Animal Science, College of Agriculture and Natural Resources, University of Tehran
3 Department of Animal Science, College of Agriculture Science, University of Mohaghegh Ardabili
4 Department of Animal Science, College of Agriculture and Natural Resources, University of Tehran
5 Department of Animal Science, Sari Agricultural Science and Natural Resources University
چکیده [English]

Introduction The compounds known as β-adrenergic agonists (β-AA) are organic molecules that have the ability to bind to β-adrenergic receptors (β-AR) and start biochemical reactions that will result in increase of accretion of skeletal muscle and reduction in accretion of fat. The anabolic responses to β-AA are temporary, with a peak time occurring during the first 14 days, after which there is a linear decline in growth response, due to either down-regulation or desensitization of the β-AR. Based on down-regulation of β-AR research, the hypothesis that intermittent feeding of β-AA could enhance response on growth performance was created. The objective of this study was therefore to ascertain the effects of continuous and intermittent use of ZH for a period of 42 d on β-AR gene expression in Lori-Bakhtiari feedlot lambs.
Materials and Methods The continuous feeding of ZH (daily regimen), intermittent 1 d feeding ZH followed by 1 d of withdrawal (1 on 1 off regimen), and intermittent 2 d feeding ZH followed by 2 d of withdrawal (2 on 2 off regimen) were employed as the different feeding methods. Thirty two Lori-Bakhtiari male lambs (initial BW=44±4.7 kg) were assigned to one of four treatments (8 lambs/treatment) based on initial BW and were fed with a diet content of 14% protein and supplemented with 0.2 mg/kg of live weight d-1ZH. The basal diet without ZH was the added control group. For evaluating gene expression, biopsy samples of the semimembranosus muscle were collected from 3 lambs per treatment before ZH supplementation on d 0, and subsequently at d 21, and d 42. Samples were rapidly frozen in liquid N2. In laboratory after total RNA isolation from muscle, the RNA was then reverse-transcribed into complementary DNA (cDNA). Real time PCR for cDNA samples was performed using an iQ5 BioRad instrument.
Results and Discussion The results of this study showed that the main effects and period × regimen interactions effect was not significant on β1 and β2-adrenergic receptors gene expression. Also there were no significant differences between treatments and control group.
Most of the physiological effects of catecholamines are due to specific interactions with β-adrenergic receptors (β -AR). The growth response to β-AA administration commonly is often reduced over time which is possibly a result of desensitization of the β-AR after chronic continuous exposure to the β-AA. The modification in the dosage of β-AA during the feeding period was previously proven to be a useful approach for compensating the reduced response in rats and lambs. Likewise, Hossner (2005) suggested that the intermittent treatment, e.g. treating for 2 days and resting for 2 days is one of the solutions for avoiding the desensitization and down-regulation of receptors. In studies evaluating mRNA responses to β-AA, no change occurred in β1-AR mRNA abundance due to β-AA treatment. Baxa et al. (2010) explained that no detectable changes of β1-AR could be attributed to generally low abundance, which results in differences hidden by sample-to-sample variation. We were unable to detect differences in the mRNA expression of β2-AR mRNA in muscle samples. The decrease in β2-AR protein expression due to ZH treatment may be in response to a posttranscriptional event.
Conclusion According to our results, it can be concluded that we could use ZH intermittently (1 on 1 off-42 d) in feedlot lambs to decrease fattening costs versus of daily administration of ZH. Further investigation is suggested to detect the alteration of β-adrenergic receptors in continuous and intermittent feeding regimens for clarifying possibly down-regulation or desensitization of them.

کلیدواژه‌ها [English]

  • β-adrenergic Receptors
  • Feedlot Lambs
  • RT-PCR
  • Zilpaterol Hydrochloride
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