飼糧粗蛋白質(zhì)水平對豬胃腸道鈣敏感受體基因表達、胃腸激素分泌及胃功能性酶活性的影響

縣怡涵 趙秀英 丁立人 孟祥龍 王 超 朱偉云 杭蘇琴

(南京農(nóng)業(yè)大學(xué)消化道微生物研究室，南京210095)

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飼糧粗蛋白質(zhì)水平對豬胃腸道鈣敏感受體基因表達、胃腸激素分泌及胃功能性酶活性的影響

縣怡涵 趙秀英 丁立人 孟祥龍 王 超 朱偉云 杭蘇琴*

(南京農(nóng)業(yè)大學(xué)消化道微生物研究室，南京210095)

本試驗旨在研究不同飼糧粗蛋白質(zhì)水平對豬胃腸道鈣敏感受體(CaSR)基因表達、胃腸激素分泌及胃功能性酶(H+-K+-ATP酶、胃蛋白酶)活性的影響，探討小腸CaSR基因表達量與血清胃腸激素濃度以及胃CaSR基因表達量與H+-K+-ATP酶和胃蛋白酶活性的關(guān)系。選擇35日齡、初始體重為(9.57±0.64) kg的“杜×長×大”雜交斷奶仔豬18頭，隨機分為3組，分別為NP組(NRC標準粗蛋白質(zhì)水平組)、MP組(較標準蛋白質(zhì)水平組降低3%粗蛋白質(zhì)水平)和LP組(較標準粗蛋白質(zhì)水平組降低6%粗蛋白質(zhì)水平)，每組6個重復(fù)，每個重復(fù)1頭仔豬。根據(jù)豬不同生長階段的營養(yǎng)需要，分別于仔豬階段(35～80日齡)飼喂粗蛋白質(zhì)水平為20%(NP組)、17%(MP組)和14%(LP組)的飼糧，生長豬階段(81～110日齡)飼喂粗蛋白質(zhì)水平為18%(NP組)、15%(MP組)和12%(LP組)的飼糧，肥育豬階段(111～160日齡)飼喂粗蛋白質(zhì)水平為16%(NP組)、13%(MP組)和10%(LP組)的飼糧，平衡飼糧的賴氨酸(Lys)、蛋氨酸(Met)、蘇氨酸(Thr)和色氨酸(Trp)水平，試驗期125 d。試驗結(jié)束后采集前腔靜脈血液，屠宰全部試驗豬后取胃食糜、胃、十二指腸、空腸和回腸組織及黏膜，測定血清胃腸激素濃度、胃食糜中胃蛋白酶和胃黏膜中H+-K+-ATP酶活性以及胃腸道各段組織中CaSR基因表達量。結(jié)果表明：1)LP組豬胃CaSR基因表達量顯著高于NP和MP組(P<0.05)，MP和LP組十二指腸及空腸CaSR基因表達量均顯著低于NP組(P<0.05)，而各組回腸CaSR基因表達量無顯著差異(P>0.05)。2)與NP組相比，MP和LP組豬血清酪酪肽(PYY)和葡萄糖促胰島素肽(GIP)濃度顯著降低(P<0.05)，MP組血清膽囊收縮素(CCK)濃度顯著升高(P<0.05)，LP組胃黏膜中H+-K+-ATP酶與胃食糜中胃蛋白酶活性顯著升高(P<0.05)。3)胃CaSR基因表達量與胃黏膜中H+-K+-ATP酶和胃食糜中胃蛋白酶活性均呈顯著正相關(guān)(P<0.05)；十二指腸CaSR基因表達量與血清GIP濃度呈顯著正相關(guān)(P<0.05)，與血清PYY濃度呈顯著正相關(guān)趨勢(0.05≤P<0.10)；空腸CaSR基因表達量與血清GIP和PYY濃度均呈顯著正相關(guān)(P<0.05)；回腸CaSR基因表達量與血清PYY濃度呈顯著正相關(guān)趨勢(0.05≤P<0.10)。綜上所述，飼糧粗蛋白質(zhì)水平降低影響豬胃腸道CaSR基因的表達，從而影響胃功能性酶活性及胃腸激素分泌。

豬；粗蛋白質(zhì)水平；鈣敏感受體；胃腸激素；H+-K+-ATP酶；胃蛋白酶

胃腸道不僅可以消化和吸收飼糧中的營養(yǎng)物質(zhì)，還可以分泌胃腸激素，對維持機體的消化功能和穩(wěn)態(tài)有重要作用。胃腸道散在分布多種內(nèi)分泌細胞，包括胃壁細胞、D細胞及胃竇G細胞等[1]，這些細胞能表達多種營養(yǎng)素感應(yīng)受體[2]，對糖類、脂肪酸、氨基酸及肽等營養(yǎng)素進行感應(yīng)，調(diào)控胃腸激素的分泌，進而影響胃腸道的消化和吸收功能[3]。鈣敏感受體(calcium sensing receptor，CaSR)基因能夠感應(yīng)氨基酸和多肽，尤其是芳香族L-氨基酸[如L-苯丙氨酸(L-Phe)和L-色氨酸(L-Try)][4-8]，且在胃腸內(nèi)分泌細胞中有廣泛的表達[3-4]。CaSR基因和H+-K+-ATP酶在胃壁細胞中均有表達，且H+-K+-ATP酶的活性受CaSR基因調(diào)控。Busque等[9]研究發(fā)現(xiàn)，大鼠胃壁細胞的CaSR基因能介導(dǎo)氨基酸，從而增強與胃酸分泌相關(guān)的H+-K+-ATP酶活性。Mace等[10]試驗發(fā)現(xiàn)，L-氨基酸能激活CaSR基因，從而促進體外培養(yǎng)的大鼠小腸葡萄糖促胰島素肽(glucose insulinotropic peptide，GIP)、酪酪肽(peptide tyrosine tyrosine，PYY)和胰高血糖素樣肽-1(glucagon-like peptide-1，GLP-1)的分泌。Liou等在研究小鼠I細胞[11]和Hira等[12]在研究小鼠STC-1細胞時均發(fā)現(xiàn)，L-Phe能夠激活CaSR基因，從而促進膽囊收縮素(cholecystokinin，CCK)的分泌。目前為止，關(guān)于蛋白質(zhì)及氨基酸對胃腸道中CaSR基因的表達及功能影響的研究主要集中在人、小鼠和大鼠等，且主要為體外試驗，而在豬的體內(nèi)研究尚未見報道。鑒此，本試驗設(shè)計了不同粗蛋白質(zhì)水平的飼糧，對豬進行長期飼喂，研究其對豬胃腸道CaSR基因表達、胃腸激素分泌及胃功能性酶活性的影響。

1 材料與方法

1.1 試驗動物與試驗設(shè)計

選擇35日齡、初始體重為(9.57±0.64) kg的“杜×長×大”雜交斷奶仔豬18頭，根據(jù)飼糧粗蛋白質(zhì)水平隨機分為3組，分別為NP組(NRC標準粗蛋白質(zhì)水平組)、MP組(較標準粗蛋白質(zhì)水平組降低3%蛋白質(zhì)水平)和LP組(較標準粗蛋白質(zhì)水平組降低6%蛋白質(zhì)水平)，每組6個重復(fù)，每個重復(fù)1頭仔豬，單欄飼養(yǎng)，自由飲水和采食。根據(jù)NRC標準(2012)配制玉米-豆粕型基礎(chǔ)飼糧，正式試驗前預(yù)飼3 d；預(yù)飼結(jié)束后，分別于仔豬階段(35～80日齡)飼喂粗蛋白質(zhì)水平為20%(NP組)、17%(MP組)和14%(LP組)的飼糧，生長豬階段(81～110日齡)飼喂粗蛋白質(zhì)水平為18%(NP組)、15%(MP組)和12%(LP組)的飼糧，肥育豬階段(111～160日齡)飼喂粗蛋白質(zhì)水平為16%(NP組)、13%(MP組)和10%(LP組)的飼糧，平衡賴氨酸(Lys)、蛋氨酸(Met)、蘇氨酸(Thr)和Trp，試驗期125 d。試驗飼糧組成及營養(yǎng)水平見表1。試驗于中國農(nóng)業(yè)科學(xué)院亞熱帶農(nóng)業(yè)研究所豬代謝室進行。試驗前對豬舍環(huán)境、用具等進行清洗、熏蒸、浸泡消毒處理。試驗期間按時進行消毒、驅(qū)蟲、免疫等工作。

表1 試驗飼糧組成及營養(yǎng)水平(飼喂基礎(chǔ))

續(xù)表2項目Items飼糧粗蛋白質(zhì)水平Dietarycrudeproteinlevel/%仔豬階段Weanedpigsperiod201714生長豬階段Growingpigsperiod181512肥育豬階段Finishingpigsperiod161310蘇氨酸Thr0.090.210.330.010.140.260.060.19色氨酸Try0.010.040.080.020.070.010.06磷酸氫鈣CaHPO40.000.741.150.690.780.900.500.550.65石粉Limestone0.520.700.790.870.890.900.550.550.55食鹽NaCl0.300.300.300.300.300.300.300.300.30預(yù)混料Premix1)1.001.001.001.001.001.001.001.001.00合計Total100.00100.00100.00100.00100.00100.00100.00100.00100.00營養(yǎng)水平Nutrientlevels2)消化能DE/(MJ/kg)14.6014.6014.6014.2014.2014.2014.2014.2014.20粗蛋白質(zhì)CP20.0517.0914.0918.2715.1612.3516.3013.1710.26賴氨酸Lys1.251.251.250.970.970.940.720.720.73蛋氨酸+半胱氨酸Met+Cys0.620.630.620.560.560.540.500.420.42蘇氨酸Thr0.760.750.760.610.600.600.560.500.49色氨酸Try0.200.200.200.170.170.170.170.130.13精氨酸Arg1.090.930.701.080.820.570.940.700.44組氨酸His0.440.370.300.410.330.250.390.310.22異亮氨酸Ile0.700.590.450.640.490.350.600.450.30亮氨酸Leu1.521.321.111.351.140.941.321.130.91苯丙氨酸Phe0.810.700.560.770.620.460.710.570.41纈氨酸Val0.720.640.540.660.560.440.610.500.36必需氨基酸EAA8.117.386.497.226.265.266.525.434.41非必需氨基酸NEAA8.727.475.988.977.265.498.026.334.61必需氨基酸/總氨基酸EAA/TAA0.480.500.520.450.460.490.450.460.49

1)預(yù)混料為每千克飼糧提供 Premix provided the following per kg of diets：VA 10 800 IU，VD34 000 IU，VE 40 IU，VK34 mg，VB16 mg，VB212 mg，VB66 mg，VB120.05 mg，生物素 biotin 0.2 mg，葉酸 folic acid 2 mg，煙酸 nicotinic acid 50 mg，D-泛酸鈣D-calcium pantothenate 25 mg，F(xiàn)e (as FeSO4) 100 mg，Cu (as CuSO4) 150 mg，Mn (as MnO2) 40 mg，Zn (as ZnO) 100 mg，I (as KI) 0.5 mg，Se (as Na2SeO3) 0.3 mg。

2)消化能、粗蛋白質(zhì)為計算值，其他營養(yǎng)水平為實測值。DE and CP were calculated values, while other nutrient levels were measured values.

1.2 樣品采集與處理

1.2.1 血清樣品

試驗結(jié)束前所有試驗豬禁食24 h，自由飲水。試驗第125天，采集所有試驗豬的前腔靜脈血液100 mL，待血液凝固后離心取上層血清，-20 ℃保存，用于胃腸激素CCK、GIP和PYY濃度的測定。

1.2.2 胃腸道樣品

采血后處死試驗豬，剖開腹腔，立即取出整個消化道，分離、結(jié)扎各部位。將胃食糜充分混勻后盡快取出，-20 ℃保存，用于胃蛋白酶活性分析。冰上剪取胃、十二指腸、空腸、回腸組織及黏膜，在磷酸鹽緩沖液(PBS)中漂去內(nèi)容物后，放入液氮中保存，用于H+-K+-ATP酶活性分析及CaSR基因表達量檢測。

1.3 測定指標及方法

1.3.1 血清胃腸激素濃度

利用酶聯(lián)免疫吸附法(ELISA)檢測試驗豬前腔靜脈血清中胃腸激素CCK、PYY和GIP的濃度，豬CCK(FU-Z044；CCK8 antibody，orb10260，biorbyt)、PYY(FU-Z240，PYY antibody，LS-C191185-400，LifeSpan BioSciences)及GIP(FU-A192；GIP antibody GTX37687 GeneTex)檢測試劑盒均購自北京方程生物科技有限公司。

1.3.2 胃功能性酶活性

嚴格按照豬胃蛋白酶和H+-K+-ATP酶的試劑盒說明書檢測胃食糜中胃蛋白酶及胃黏膜中H+-K+-ATP酶活性，胃蛋白酶(A080-1)和H+-K+-ATP酶(A069)試劑盒均購自南京建成悅浩科技有限公司。

1.3.3CaSR基因表達量

1.4 數(shù)據(jù)統(tǒng)計與分析

試驗數(shù)據(jù)經(jīng)Excel 2010初步整理后，采用SPSS 20.0軟件中的單因素方差(one-way ANOVA)模型進行分析，S-N-K test進行差異顯著性檢驗，P<0.05為差異顯著，P<0.01為差異極顯著；采用GraphPad Prism 5分析胃腸道中CaSR基因表達量與胃黏膜中H+-K+-ATP酶、胃食糜中胃蛋白酶活性及血清中胃腸激素濃度的相關(guān)關(guān)系，P<0.05為顯著相關(guān)，0.05≤P<0.10為呈顯著相關(guān)趨勢。

2 結(jié) 果

2.1 飼糧粗蛋白質(zhì)水平對豬胃腸道CaSR基因表達量的影響

由圖1可以看出，在胃中，LP組CaSR基因表達量顯著高于NP和MP組(P<0.05)，NP與MP組差異不顯著(P>0.05)；十二指腸及空腸中，MP和LP組CaSR基因表達量均顯著低于NP組(P<0.05)，MP與LP組差異不顯著(P>0.05)；而回腸各組CaSR基因表達量無顯著差異(P>0.05)。

同一組織數(shù)據(jù)柱形標注無字母或相同字母者表示差異不顯著(P>0.05)，不同小寫字母者表示差異顯著(P<0.05)。

Data columns of the same tissue with no letter or the same letter superscripts mean no significant difference (P>0.05), while with different small letter superscripts mean significant difference (P<0.05).

圖1 飼糧粗蛋白質(zhì)水平對豬胃腸道CaSR基因表達量的影響

Fig.1 Effects of dietary crude protein level onCaSRgene expression level of gastrointestinal tract of pigs

2.2 飼糧粗蛋白質(zhì)水平對豬血清胃腸激素濃度及胃功能性酶活性的影響

由表2可以看出，與NP組相比，MP和LP組豬血清PYY和GIP濃度顯著降低(P<0.05)，MP與LP組無顯著差異(P>0.05)；MP組血清CCK濃度顯著升高(P<0.05)，LP組無顯著變化(P>0.05)；LP組胃黏膜中H+-K+-ATP酶與胃食糜中胃蛋白酶活性顯著升高(P<0.05)，MP組未表現(xiàn)出顯著變化(P>0.05)。

2.3 豬胃腸道CaSR基因表達量與血清胃腸激素濃度和胃功能性酶活性相關(guān)性分析

由表3可以看出，胃中CaSR基因表達量與胃黏膜中H+-K+-ATP酶和胃食糜中胃蛋白酶活性均呈顯著正相關(guān)(P<0.05)；十二指腸CaSR基因表達量與血清GIP濃度呈顯著正相關(guān)(P<0.05)，與血清CCK濃度無顯著相關(guān)性(P>0.05)，與血清PYY濃度呈顯著正相關(guān)趨勢(0.05≤P<0.10)；空腸CaSR基因表達量與血清GIP和PYY濃度均呈顯著正相關(guān)(P<0.05)，與血清CCK濃度無顯著相關(guān)性(P>0.05)；回腸CaSR基因表達量與血清CCK和GIP濃度均無顯著相關(guān)性(P>0.05)，與血清PYY濃度呈顯著正相關(guān)趨勢(0.05≤P<0.10)。

表2 飼糧粗蛋白質(zhì)水平對豬血清胃腸激素濃度及胃功能性酶活性的影響

同行數(shù)據(jù)肩標相同或無字母表示差異不顯著(P>0.05)，不同小寫字母表示差異顯著(P<0.05)，不同大寫字母表示差異極顯著(P<0.01)。

In the same row, values with the same or no letter superscripts mean no significant difference (P>0.05), while with different small letter superscripts mean significant difference (P<0.05), and with different capital letter superscripts mean significant difference (P<0.01).

表3 豬胃腸道CaSR基因表達量與血清胃腸激素濃度、H+-K+-ATP酶及胃蛋白酶活性相關(guān)性分析

數(shù)據(jù)肩標*表示顯著相關(guān)(P<0.05)。

Values with * mean significant correlation (P<0.05).

3 討 論

CaSR基因在嚙齒類動物消化道諸多部位中廣泛表達，包括食管、胃、小腸[15]。本研究發(fā)現(xiàn)CaSR基因在豬胃及小腸各部位均有表達。飼糧粗蛋白質(zhì)的降解產(chǎn)物主要為小肽和氨基酸[2]，這些降解產(chǎn)物能夠激活CaSR[10,16]。Conigrave等[17-18]發(fā)現(xiàn)，細胞外鈣離子處于一定濃度下，芳香族氨基酸可以調(diào)節(jié)CaSR的活性，且隨著氨基酸濃度的升高，CaSR基因表達量也隨之升高。本研究發(fā)現(xiàn)，當飼糧粗蛋白質(zhì)水平降低時，胃CaSR基因表達量升高，這可能是因為飼糧中平衡的4種氨基酸(Lys、Met、Thr和Try)中含有可以激活CaSR基因的Try(隨著飼糧粗蛋白質(zhì)水平的降低色氨酸添加量增加)，飼糧進入胃中粗蛋白質(zhì)尚未降解為氨基酸，所以額外添加的Try含量越高，對CaSR的激活作用越強，CaSR基因表達量則越高；十二指腸和空腸的CaSR基因表達量隨飼糧粗蛋白質(zhì)水平的降低而降低，可能是由于飼糧中粗蛋白質(zhì)在胃中經(jīng)過消化后產(chǎn)生的部分肽以及氨基酸進入小腸后激活了十二指腸和空腸的CaSR基因而使其表達量升高；而回腸的CaSR基因表達量雖隨著粗蛋白質(zhì)水平的降低而略有降低，但并未表現(xiàn)出顯著變化，這可能是因為氨基酸在十二指腸和空腸中已經(jīng)被大量消化吸收，到達回腸的氨基酸濃度較低，故未能調(diào)控CaSR的基因表達量。

研究表明，CaSR基因在胃壁細胞中表達量較高[19-20]，L-芳香族氨基酸可以激活CaSR基因，從而增強H+-K+-ATP酶和胃蛋白酶活性[9,21]。本研究中，隨著飼糧粗蛋白質(zhì)水平的降低，色氨酸添加量逐漸增加，胃蛋白酶與H+-K+-ATP酶的活性升高；相關(guān)性分析顯示，隨著豬胃CaSR基因表達量的升高，H+-K+-ATP酶與胃蛋白酶活性隨之升高，二者存在顯著正相關(guān)，與上述研究結(jié)果一致。研究還發(fā)現(xiàn)，隨著粗蛋白質(zhì)攝入水平的增加，人體內(nèi)的GIP、PYY等激素的分泌增加[22]。本研究結(jié)果表明，隨飼糧粗蛋白質(zhì)水平的降低，胃腸激素PYY、GIP的分泌也降低。研究也表明，氨基酸對大鼠小腸GIP、CCK、PYY的分泌有促進作用，CaSR特異性激活劑NPS R568可以顯著增強這種作用，而CaSR特異性抑制劑Calhex 231顯著抑制這種作用[11]。據(jù)此，本試驗將豬小腸CaSR基因表達量與胃腸激素進行了相關(guān)性分析，結(jié)果顯示，除CCK外，其余胃腸激素與十二指腸和回腸的CaSR基因表達量呈顯著或趨于顯著的正相關(guān)關(guān)系。當飼糧粗蛋白質(zhì)水平降低時，小腸中蛋白質(zhì)水解產(chǎn)生的氨基酸的水平降低，使CaSR對氨基酸的敏感性降低，導(dǎo)致胃腸激素分泌量下降。以上結(jié)果初步表明，氨基酸可以通過激活CaSR調(diào)節(jié)胃腸激素分泌、胃蛋白酶及H+-K+-ATP酶活性。Shi等[23]和Leray等[24]研究表明，飼糧中粗蛋白質(zhì)水平降低會促進胃腸道CCK的釋放。本研究中，蛋白質(zhì)水平降低3%，小腸CaSR基因表達量降低，但CCK的分泌量有所升高，可能是由于營養(yǎng)攝入不足所產(chǎn)生的代償性反應(yīng)，以保證在低蛋白質(zhì)水平的情況下，機體仍能保持穩(wěn)定的狀態(tài)。目前，由于體內(nèi)環(huán)境復(fù)雜，影響因素多，有關(guān)蛋白質(zhì)及其水解產(chǎn)物與CaSR對胃腸激素分泌作用的影響在機體內(nèi)的研究甚少。鑒此，在后續(xù)研究中，課題組計劃采用體外灌流技術(shù)研究豬胃腸道CaSR基因表達量與胃腸激素分泌的關(guān)系，并利用免疫組化及免疫熒光技術(shù)探究氨基酸激活CaSR調(diào)節(jié)胃腸激素分泌、胃功能性酶活性的信號通路，揭示豬胃腸道CaSR基因表達量與胃腸激素分泌和胃功能性酶活性之間的關(guān)系及其機制。

4 結(jié) 論

綜上所述，當飼糧中粗蛋白質(zhì)水平降低時會影響豬胃腸道中CaSR基因的表達量，從而影響部分胃腸激素(GIP、PYY)的分泌以及胃功能性酶(胃蛋白酶、H+-K+-ATP酶)活性。

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*Corresponding author, professor, E-mail: suqinhang69@njau.edu.cn

(責(zé)任編輯 李慧英)

Effects of Dietary Crude Protein Level on Calcium Sensing Receptor Gene Expression of Gastrointestinal Tract, Gastrointestinal Hormone Secretion and the Activities of Gastric Function Enzymes of Pigs

XIAN Yihan ZHAO Xiuying DING Liren MENG Xianglong WANG Chao ZHU Weiyun HANG Suqin*

(Laboratory of Gastrointestinal Microbiology, Nanjing Agricultural University, Nanjing 210095, China)

The experiment was conducted to investigate the effects of different dietary crude protein (CP) levels on calcium sensing receptor (CaSR) gene expression of gastrointestinal tract, gastrointestinal hormone secretion and the activities of gastric function enzymes (pepsin and H+-K+-ATPase) of pigs, and to explore the relationships betweenCaSRgene expression level of small intestine and the concentration of gastrointestinal hormone in serum,CaSRgene expression level of stomach and the activities of H+-K+-ATPase and pepsin, respectively. Eighteen 35-day-old “Duroc×Landrace×Large White” crossed weaned pigs with initial body weight of (9.57±0.64) kg were randomly assigned into 3 group with 6 replicates per group and 1 pig per replicate, including NP group (NRC standard CP level group), MP group (decreased 3% CP level compared to the standard CP level group) and LP group (decreased 6% CP level compared to the standard CP level group). According to the nutrient needs of pigs in different growth periods, pigs were fed diets contained 20% (NP group), 17% (MP group) and 14% (LP group) CP levels in weaned pigs period (35 to 80 days of age), respectively; diets contained 18% (NP group), 15% (MP group) and 12% (LP group) CP levels in growing pigs period (81 to 110 days of age), respectively; diets contained 16% (NP group), 13% (MP group) and 10% (LP group) CP levels in finishing pigs period (111 to 160 days of age), respectively. The levels of dietary lysine (Lys), methionine (Met), threonine (Thr) and tryptophan (Trp) were balanced. The experimental period lasted for 125 days. Precaval vein blood were collected by the end of the experiment, then all pigs were slaughtered, and gastric chyme, stomach, duodenum, jejunum and ileum tissues and mucosa were collected, to determination of the concentration of gastrointestinal hormones in serum, the activities of pepsin of gastric chyme and H+-K+-ATPase of gastric mucosa andCaSRgene expression level of each tissues of the gastrointestinal tract. The results showed as follows: 1)CaSRgene expression level of stomach of pigs in LP group was significantly higher than that in NP and MP groups (P<0.05), andCaSRgene expression level of duodenum and jejunum in MP and LP groups was significantly lower than that in NP group (P<0.05), but no significant difference was found inCaSRgene expression level of ileum among all groups (P>0.05). 2) Compared with NP group, the concentrations of peptide tyrosine tyrosine (PYY) and glucose insulinotropic peptide (GIP) in serum of pigs in MP and LP groups were significantly decreased (P<0.05), the concentration of cholecystokinin (CCK) in serum in MP group was significantly increased (P<0.05), and the activities of pepsin of gastric chyme and H+-K+-ATPase of gastric mucosa in LP group were significantly increased (P<0.05). 3)CaSRgene expression level in stomach had a significantly positive correlations with the activities of pepsin of gastric chyme and H+-K+-ATPase of gastric mucosa (P<0.05),CaSRgene expression level in duodenum had a significantly positive correlation with the concentration of GIP in serum (P<0.05), and had a positive correlation tendency with the concentration of PYY in serum (0.05≤P<0.10),CaSRgene expression level in jejunum had a significantly positive correlations with the concentrations of GIP and PYY in serum (P<0.05), andCaSRgene expression level in ileum had a positive correlation tendency with the concentration of PYY in serum (0.05≤P<0.10). In conclusion, reduction of dietary CP level affectsCaSRgene expression of gastrointestinal tract, the activities of gastric function enzymes and gastrointestinal hormone secretion.[ChineseJournalofAnimalNutrition, 2016, 28(11)：3634-3641]

pigs; crude protein level; calcium sensing receptor; gastrointestinal hormone; H+-K+-ATPase; pepsin

2016-05-12

國家973項目(2013CB127301)資助

縣怡涵(1992—)，女，甘肅天水人，碩士研究生，從事動物營養(yǎng)與胃腸道健康方面的研究。E-mail: 2014105006@njau.edu.cn

*通信作者：杭蘇琴，教授，碩士生導(dǎo)師，E-mail: suqinhang69@njau.edu.cn

10.3969/j.issn.1006-267x.2016.11.033

S828

A

1006-267X(2016)11-3634-08