生长激素释放因子(GRF)在动物肌肉组织的表达

向大鼠后肢小腿前部注射生长激素释放因子 ( GRF)的表达质粒 pc DNA3 -GRF4 0 μg,于注射后 2 d开始 ,每隔 5d杀 2只取样 ,提取 RNA和 DNA,用 PCR和 RT-PCR检测质粒及其表达。结果表明 ,在 3 0 d时仍为阳性结果。注射部位肌肉组织免疫组化检测结果表明 ,在部分大鼠 ( 1 4/ 2 4 )的肌肉组织中检测到了 GRF分子。给家兔注射 pc DNA3 -GRF质粒 1 0 0μg(第 组注射质粒 ,第 组注射含 1 0 %甘油的质粒 ) ,于注射后 1 d开始采血分离血清 ,用 RIA法测定血清生长激素 ( GH)的水平。结果表明 ,第 组在 5d时 ,GH水平上升2 7.1 %( P <0 .0 5)。本研究结果表明 ,外源 GRF在肌肉组织可获得表达 ,并能提高动物体内的 GH水平     

活体电穿孔方法提高外源GRF基因在小鼠肌肉组织中的表达

向小鼠后肢小腿肌注pGRF表达质粒并加以电穿孔条件,注射剂量分别为5,10,50μg,于注射前及注射后10,20,30d测体质量,并采血分离血清测血清GRF水平。结果显示,5μgpGRF质粒电穿孔组注射后10dGRF分别比对照组、5μgpGRF质粒组升高44.73%(P0.05),12.86%(P0.05);血清中GRF水平升高。30d累积增重,5μgpGRF质粒电穿孔组分别比对照组、5μgpGRF质粒组高11.46%,6.75%(P0.05);10μgpGRF质粒组分别比对照组和10μgpGRF质粒电穿孔组高19.52%(P0.05),19.42%(P0.05)。50μgpGRF质粒组45d累积增重分别比对照组、pGRF质粒电穿孔组高14.00%,12.00%(P0.05)。结果表明,电穿孔处理可提高GRF基因在小鼠肌肉中的表达。     

肌注猪促生长激素释放因子(pGRF)基因质粒后猪神经内分泌生长轴激素的变化规律

试验探讨pGRF基因质粒在猪体内的表达效应及作用机理。将10头体重相近([15.24±0.53)kg]、遗传基础相似的健康杜×长×大三元杂交阉公猪安装颈静脉血导管,随机分成2组。试验开始时,试验组每头猪左侧臀部肌肉注射4.5mgpGRF基因质粒,第30d时,试验组每头猪右侧臀部肌肉注射相同剂量pGRF基因质粒,对照组两次分别注射2ml生理盐水。测定采样血浆中GRF、SS、GH及IGF-I的浓度。结果表明:①第一次注射pGRF基因质粒8d时,试验组GH的水平较对照组有显著提高(P<0.05),第12dGH水平达最高,为对照组的157%(P<0.01);第8、12、17、22d的IGF-I水平分别为对照组的185%(P<0.01)、237%(P<0.01)、200%(P<0.01)、131%(P<0.05);第12d试验组的SS水平较对照组有明显下降(P<0.05),其余时间无明显变化;GRF的水平在第12d分泌量达到最高,为对照组的143%(P<0.01),17d为对照组的133%(P<0.05),此后逐步下降又上升,与对照组的水平差异不显著。②在此试验条件下,基因质粒在5～8d开始缓释表达,12d左右达到表达高峰,其有效剂量持续时间在20d以上。③第二次注射基因质粒后,试验组第33d以后GH的水平逐渐升高,到45dGH水平达到峰值,为对照组的144%(P<0.05);第39、45、60d的IGF-I水平分别为对照组的166%(P<0.05)、173%(P<0.05)、117%(P<0.05);GRF的水平在45d分泌量达到最高,为对照组的138%(P<0.05),其余时间无明显变化;SS水平较对照组无显著差异。④相关分析表明:注射基因质粒后,试验组GH与GRF的相关系数为0.81(P<0.01),与SS的相关系数为-0.65(P>0.05);GH、GRF与IGF-I存在着正相关,SS与IGF-I存在负相关性,除GH与IGF-I的相关系数为0.67,达到显著正相关水平(P<0.05),其余指标与IGF-I均未有显著相关。     

注射pGRF基因质粒对猪血清生长轴激素变化规律的影响

本研究旨在探讨注射pGRF基因质粒在猪体内的表达效应及作用规律.试验选择8头体质量相近((15 0.43)kg)的健康长白×大白二元杂交阉公猪,随机分成2组.试验组颈部肌肉注射含4.5 mg pGRF基因质粒的注射液2 mL,对照组注射生理盐水2 mL.于处理后第1、4、7、11、16、21、26、31天空腹采血样制备血清,测定血清中生长激素(GH)、类胰岛素生长因子(IGF-I)、生长激素释放因子(GRF)、生长抑素(SS)的含量.结果表明:试验组在注射pGRF基因质粒后第7天,血清GH含量达峰值,比对照组高了113.47%,差异极显著(P<0.01);然后逐渐下降.到第11天时,比对照组高47.09%,差异显著(P<0.05).到第31天时,与对照组基本一致.试验组血清IGF-I和GRF含量虽然提高幅度不大,但其变化与GH含量存在着显著相关性,均在注射pGRF基因质粒后第7天达到峰值,然后降至对照组水平,其相关系数分别为0.589(P<0.05)和0.678(P<0.05).与对照组相比,试验组血清SS含量在11 d前一直呈下降趋势,第11天时降至最低点,但差异不显著.到第16天时2组均有所上升,21 d后缓慢下降,第31天时与对照组趋于一致.血清SS含量与GH、GRF的含量分别存在显著和极显著负相关,相关系数分别为-0.689(P<0.05)和-0.777(P<0.01).由此可见,pGRF基因质粒在体内快速表达并作用于机体,主要通过提高GRF的含量而促使GH的分泌,同时抑制SS的分泌,一定程度阻止其对GRF和GH的抑制作用,从而达到有效的促生长作用.同时本试验发现,虽然采用了颈静脉导管方法,猪血液中生长轴激素测定值变异仍较大,加强护理和增加测试猪的数量是取得更为客观结果的必要条件.     

仔猪骨骼肌注射pGRF基因质粒的促生长及代谢调控效应研究

给体重约 5 0kg的长白×太湖仔猪以 0 2 5、0 5、1 0、2 0mg剂量半腱肌部位注射 pGRF基因的表达质粒 ,5～ 10kg阶段终体重分别比 0mg组增加 4%、17%、2 0 %和 16 % ,日增重增加 8%、37%、43%和 36 % ,采食量提高 17%、2 7%、2 3 %和 11% ;耗料增重比 ,0 5mg组、1 0mg组及 2 0mg组分别比 0mg组降低 8%、14%和 18%。1 0mgpGRF基因质粒使血液中生长激素释放因子 (GRF)比对照组升高 1 6倍 (P <0 0 5 )、生长激素 (GH)升高2 5倍 (P <0 0 1)、类胰岛素生长因子 (IGF Ⅰ )升高 2 3倍 (P <0 0 1) ,血液中尿素浓度降低 2 0 % (P <0 0 5 ) ,血液中甘油三酯浓度 (TG)明显下降 (P <0 0 5 )。试验研究还证明生长抑素 (SS)分泌的增加是限制 pGRF基因质粒高用量时正效应发挥的重要因素 ,1mg为 5～ 10kg阶段仔猪注射 pGRF基因质粒的适宜剂量。     

饲养水平对注射生长激素的肉牛生长性能、血清胰岛素样生长因子、胰岛素样生长因子结合蛋白的影响

本研究旨在测定饲养水平及生长激素水平对架子牛生长性能、饲料转化率 (增重∶饲料为 G∶ F) ,胴体成分 ( BC)、血清生长激素 ( ST)、IGF 和 IGF结合蛋白 ( BP)的影响。为期 2年的试验中 ,40头架子牛按体重(平均体重 BW为第 1年为 3 1 6kg,第 2年 3 0 5 kg)采用 2× 2拉丁方试验设计 ,主因子为 b ST( 0或 3 3μg/kg BW.d) ,饲养水平为自由采食 ( AL )或限制饲喂 ( 0 .75 AL)。注射 b ST日增重 ( ADG)为 1 .2 5 kg/d,比非注射组 ( 1 .1 4kg/d)提高 9.6% ( P<0 .0 5 ) ;自由采食组 ( AL)日增重1 .3 9kg/d比 0 .75 AL组 ADG提高 3 9% ( P<0 .0 5 ) ,且饲料转化率 G∶ F提高 8.1 % (由 1 2 .3提高到 1 3 .3 g/kg,P<0 .0 5 )。 b ST和饲养水平具有互作效应 ( P=0 .0 1 ) ,注射b ST的自由采食 ( AL)组日增重 ( 1 0 .6% )高于 0 .75 AL组 ADG( 7.8% ) ( P=0 .1 0 ) ,0 .75 AL 组肉牛的血清生长激素 ( ST)水平 ( 1 3 .0 ng/ml)高于 AL组 ( 8.6ng/ml) ( P<0 .0 5 ) ,b ST处理组血清生长激素 ( ST)水平 ( 1 6.3 ng/ml)高于 b ST未处理组 5 .2 ng/ml( P<0 .0 5 )。由于 b ST×饲养水平的互作效应 ,外源 b ST对提高 0 .75 AL组血清ST的作用大于 AL组 ( P<0 .0 1 ) ,b ST处理组与未处理组相比 ,血清 IGF- 、IGFBP-3升     

生长肥育猪骨骼肌注射表达pGRF基因质粒的效应研究

将猪的GRF基因表达质粒注射于猪的骨骼肌后,研究其促生长效应与机理。选用始重6.3kg的44头去势长白×太湖仔猪,分6组,采用2×3因子安排的完全随机区组设计,按6～10kg、10～20kg、20～50kg、50～100kg4个阶段饲养。4个饲养阶段的饲粮低蛋白水平分别是20.70%,17.90%,15.03%,13.00%;高蛋白水平分别是23.70%,20.90%,18.02%,16.00%。pGRF基因质粒注射剂量设0mg、0.5mg、1.0mg3个水平,于试验开始与试验猪体重达60kg时共注射基因质粒2次。测定各阶段日增重,饲料消耗量,耗料增重比以及30、70、100kg时血液中GH、GRF、IGF-I的浓度。100kg时屠宰进行胴体品质测定。结果表明:饲粮蛋白水平对各阶段及全期试验猪日增重均有显著影响(P<0.05或P<0.01),对50～100kg阶段与全期日采食量和耗料增重比有显著影响(P<0.05或P<0.01)。注射pGRF基因质粒对各阶段及全期日增重均有显著影响(P<0.05),对6～10kg、10～20kg、50～100kg3阶段及全期日采食量有显著影响(P<0.05),对6～10kg阶段、50～100kg阶段及全期耗料增重比有显著影响(P<0.05)。注射pGRF基因质粒对30kg及70kg体重时猪血液中GRF、GH、IGF-I浓度均有显著影响(P<0.05)。提高饲粮蛋白水平与注射pGRF基因质粒均可明显降低超声波测膘厚及屠宰测膘厚、增大眼肌面积(P<0.05)。     

原生质体介导的外源性GRF基因对小鼠增重的研究

生长激素释放因子 (GRF)是由动物下丘脑合成并分泌的一种多肽激素 ,能特异性的诱导生长激素的合成与分泌 ,提高体内生长激素的水平 ,从而促进动物的生长。本实验是将含GRF重组质粒的 JM1 0 9菌株大量培养 ,制备原生质体 (所含质粒进行定量 ) ,用 1 0 m L / L的戊二醛处理后 ,注射于小鼠后肢胫骨部肌肉 ,给予电刺激。与含有 GRF基因的裸质粒注射组对比观察对小鼠增长的影响。研究结果表明 :原生质体能够与小鼠肌肉细胞融合 ,同时 ,以原生质体介导的外源性 GRF基因可以提高小鼠的增长速度 ,其效果与裸质粒无显著差别。 1 0 0 V,50ms的低压、短脉冲电刺激对 GRF在动物体内的表达量上无显著差异     

表达PRRSV E基因重组质粒在小鼠诱导的体液免疫应答

利用 PCR技术对猪繁殖与呼吸综合征病毒 (PRRSV) BJ- 4株的 E基因进行修饰和改造 ,在 E基因上游加入 Kozak序列 ,扩增并克隆 E基因。将 E基因 c DNA亚克隆至真核表达载体 pc DNA3.1( )中 ,构建了真核重组表达质粒 pc DNA- E。用pc DNA- E免疫小鼠 ,经免疫荧光抗体试验检测结果表明 ,重组质粒 pc DNA- E经 3次免疫后 ,所有小鼠血清抗体均为阳性 ,说明pc DNA- E在小鼠体内可诱导特异性的体液免疫应答反应。     

肾上腺素能α2受体对二花脸猪生长激素分泌的作用

给 6头去势二花脸公猪一次注射肾上腺素能α2 受体激动剂可乐宁 ( Clonidine,6μg/ kg)后 ,GH总体水平、基础水平、峰强度明显升高 ,分别增加 10 4 .10 % ( P<0 .0 1)、113.4 0 % ( P<0 .0 1)和 5 4 .5 0 % ( P<0 .0 1) ,并保持脉冲式分泌 ,但峰值出现在注射后 6 0 min左右 ,明显提前。饲喂半胱胺 ( CS)后第 4天静脉注射 Clonidine,则 GH分泌比对照组显著提高 ,但与单独注射 Clonidine和单独口服 CS相比较未见有显著差异 ( P>0 .0 5 )。结果表明 ,α2 受体激动剂 Cloni-dine可促进 GH分泌 ,且峰值出现时间明显提前     

生长激素释放因子在CHO细胞的表达

在对生长激素释放因子 (GRF)基因改造和化学合成 ,并构建了其真核表达载体 pc DNA3- GRF(1- 32 )的基础上 ,用 L ipofectin将上述载体转染 CHO细胞进行瞬时表达。提取转染细胞总 RNA,用 RT- PCR和 Dot blotting检测 GRF基因的表达情况 ,用 Western blotting检测转染细胞上清液的表达产物 ,均得到了阳性结果。制备大鼠垂体单层细胞 ,测定表达产物的生物学活性 ,结果表达产物可刺激生长激素释放 ,并且比对照组提高 3.8倍。试验结果表明 ,已构建的真核表达载体 pc DNA3- GRF(1- 32 )能表达出有生物学活性的 GRF。     

生长激素释放因子肝脏定向表达复合物在家兔体内的表达

外源基因在体内的转染及表达存在转染效率低、表达时间短等缺点，利用受体介导基因转移技术，可以将基因定向转入到特定组织，并且能提高转染效率和表达时间。在本试验中，利用肝脏去唾液酸糖蛋白受体(ASGR)将生长激素释放因子(GRF)基因定向转入到家兔肝脏组织并得到了表达。首先通过DNA阻滞试验确定质粒DNA与多聚赖氨酸(poly—L—lysine，PLL)的结合比例及反应液的最佳NaCl浓度，然后将PLL与α—D-吡喃半乳糖苯基异硫氰酸盐(α—D—galactopyranosylphenyl isotlhiocyanate)(物质的量之比为8：1)在pH9．0的Na2CO3溶液中进行糖基化反应，得到糖基化的PLL(galPLL)后透析除去未反应的糖并测定反应物糖含量。将糖基化的PLL与克隆有GRF基因的pcDNA3-GRF质粒(质量比为3．16：1)在1．031mol／L的NaCl溶液中进行连接，最终得到DNA—galPLL复合物，电镜观察其结构。耳缘静脉注射质粒复合物到家兔体内(1．5mg／只)，用RT—PCR和ELISA检测不同组织的表达情况。结果注射后7d家兔的肝脏RT—PCR结果呈阳性，27d仍能检测到GRF蛋白，但同时在其他的组织也检测到表达。并且进行了增重试验，发现定向转移GRF基因到家兔的肝脏对家兔的生长有一定的促进作用。     

Effect of triglycerides on growth hormone (GH)-releasing factor-mediated GH secretion in newborn calves

The effect of triglycerides (Tg) on GRF-mediated GH secretion was examined in 2 groups of twelve ten-day old male calves. Twelve calves were intravenously infused with a lipid-heparin solution (5 mg Tg and 0.3 IU heparin/kg body wt/min for 90 min). The twelve control calves received in the same way, the same volume of saline. Thirty minutes after the start of infusion, GRF 1–29 (human amide, 0.16 μg/kg body wt) was intravenously injected in six animals of each group.

Mean plasma GH levels reached peak concentrations in the 2 groups 5 min after GRF injection. However the area under the GH response curve, when lipid-heparin was given, was significantly diminished compared to the response when saline was given. In the same time, lipid-heparin treatment increased plasma SRIF concentration. These data suggest that an increase in plasma Tg concentration, induced by lipid-heparin infusion, inhibits GRF-mediated GH secretion, possibly through stimulation of SRIF secretion.     

Effect of human growth hormone-releasing factor on bone and mineral metabolism in growing pigs

Little information is available on the effects of growth hormone (GH) and growth hormone-releasing factor (GRF and GHRH) treatment on bone metabolism in pigs. Thus, tibial bending moments and ash contents were studied in 12, 6-wk-old pigs weighing 13 +/- .2 kg. Six pigs (GRF group) were injected s.c. twice daily with 75 micrograms GRF (hGRF [1-29] NH2)/kg BW for 52 d and six remained untreated (control group, C). Average daily gain was slightly (5%; P less than .10) increased in treated pigs. At slaughter, plasma measurements related to calcium homeostasis, such as concentrations of Ca, inorganic P, and vitamin D metabolites (25-OH and 1,25-(OH)2 vitamin D3), were not changed by GRF injection. At slaughter, plasma GH levels were 3.3 times greater in treated (11.3 +/- 3 ng/ml) than in untreated pigs (3.4 +/- .5 ng/ml, P less than .02), whereas those of insulin-like growth factor I were increased by approximately 38%. No difference was observed between the two groups at slaughter in tibial weight, density, bending moment, ash relative to bone volume (29 +/- 1 vs 30 +/- 2 g/100 cm3, GRF vs C), total ash content, or ash relative to dry matter in cortical or medullary bone. Our GRF treatment did not affect bone and mineral metabolism in young, growing pigs.     

Effect of daily injections of growth hormone-releasing factor and thyrotropin-releasing hormone on growth and endocrine parameters in chickens

The control of growth is a complex mechanism regulated by several metabolic hormones including growth hormone (GH) and thyroid hormones. In avian species, as well as in mammals, GH secretion is regulated by hypothalamic hypophysiotropic hormones. Since thyrotropin-releasing hormone (TRH) and growth hormone-releasing factor (GRF) are potent GH secretagogues in poultry, we were interested in determining the influence of daily intravenous administration of either peptide or both simultaneously on circulating GH and IGF-I concentrations and whether an improvement in growth rate or efficiency would be obtained.

Male broiler chicks were injected once daily for a period of 21 days with either GRF (10 μg/kg), TRH (1 μg/kg) or both GRF and TRH (10 and 1 μg/kg respectively) between four and seven weeks of age. On the last day of the experiment, following intravenous injection of TRH, GRF or a combination of GRF and TRH, plasma GH levels were significantly (P<.05) increased to a similar extent in control chicks and in those which had received daily peptide injections for the previous 21 days. Circulating GH levels between 10 and 90 min post-injection were significantly (P<.05) greater and more than additive than GH levels in chicks injected with both GRF and TRH when compared to those injected with either peptide alone. Mean plasma T₃ concentrations during that same time period were significantly elevated (P<.05) above saline-injected control chick levels in birds treated with TRH or GRF and TRH respectively, regardless of whether the chicks had received peptide injections for the previous 21 days. There was no evidence of pituitary refractoriness to chronic administration of either TRH or GRF injection in terms of growth or thyroid hormone secretion.

Despite the large elevation in GH concentration each day, growth rate, feed efficiency and circulating IGF-I concentrations were not enhanced. Thus the quantity or secretory pattern of GH secretion induced by TRH or GRF administration was not sufficient to increase plasma IGF-I concentration or growth.     

Effects of Long-term Growth Hormone-releasing Factor Administration on Plasma Growth Hormone, Luteinizing Hormone and Progesterone Profiles in Growing Female Buffaloes (Bubalus bubalis)

To investigate the effects of long-term growth hormone-releasing factor (GRF) administration on plasma growth hormone (GH), LH and progesterone and body weight gain in growing buffalo calves, 12 female Murrah buffaloes within the age group of 6-8 months of age were divided into two groups (treatment and control groups) of six each in such a way so that average body weights between the groups did not differ (p > 0.05). Control buffaloes were not given any hormonal treatment and treatment group buffaloes were treated with synthetic bovine GRF [bGRF (1-44)-NH(2)] at the rate of 10 microg/100 kg body weight intravenously at an interval of 15 days from week 6 (5-week pre-treatment period) till 18 injections were completed (week 6-42 treatment period) and thereafter, effect of exogenous GRF were observed for 10-week post-treatment period. Jugular blood samples were drawn twice a week at 3-4-day intervals for plasma GH, LH and progesterone quantification. Body weight of all animals was recorded twice a week. During pre-treatment period, mean plasma GH, LH and progesterone did not differ (p > 0.05) between the groups. But during treatment as well as post-treatment period, mean plasma GH levels were found to be significantly (p < 0.01) higher in treatment than control group of buffaloes. Administration of GRF for longer term sustained a higher level of plasma GH even after cessation of treatment. GRF-treated buffaloes attained higher (p < 0.01) body weight than the controls. Repeated GRF administration for long-term significantly (p < 0.01) increased plasma LH and progesterone. In conclusion, repeated long-term exogenous GRF administration induces and even enhances GH release without any sign of refractoriness. GRF may, therefore, be used to induce daily GH release without loss of responsiveness over an extended period of time in young growing female buffaloes and it may assist these animals to grow faster.     

生长激素分泌释放的生物技术调控

生长激素是调节动物生长的众多激素中最重要的一种。调控动物生长激素分泌释放是调控动物生长的重要方式。本文综述了目前存在的运用生物技术调控动物生长激素分泌释放的方法 ,包括 :注射外源生长激素、注射外源生长激素释放因子、生长抑素免疫、转GH GRF基因动物以及GRF基因直接转移 ,并指出GRF基因直接转移是最有前途的调控动物生长激素分泌释放的方法。     

Effect of long-term administration of porcine growth hormone-releasing factor and(or) thyrotropin-releasing factor on growth hormone, prolactin and thyroxine concentrations in growing pigs

Long-term administration of porcine growth hormone-releasing factor (pGRF(1-29)NH2) and(or) thyrotropin-releasing factor (TRF) was evaluated on serum concentrations of growth hormone (GH) thyroxine (T4) and prolactin (PRL). Twenty-four 12-wk-old female Yorkshire-Landrace pigs were injected at 1000 and 1600 for 12 wk with either saline, pGRF (15 micrograms/kg), TRF (6 micrograms/kg) or pGRF + TRF using a 2 x 2 factorial design. Blood samples were collected on d 1, 29, 57 and 85 of treatment from 0400 to 2200. Areas under the GH, T4 and PRL curves (AUC) for the 6 h (0400 to 1000) prior to injection were subtracted from the postinjection periods (1000 to 1600, 1600 to 2200) to calculate the net hormonal response. The AUC of GH for the first 6 h decreased similarly (P less than .05) with age for all treatments. The GH response to GRF remained unchanged (P greater than .10) across age. TRF alone did not stimulate (P less than .05) GH release but acted in synergy with GRF to increase (P less than .05) GH release. TRF stimulated (P less than .001) the net response of T4 on all sampling days. Animals treated with the combination of GRF + TRF showed a decreased T4 AUC during the first 6 h on the last three sampling days. Basal PRL decreased (P less than .05) with age. Over the four sampling days, animals injected with TRF alone showed (P less than .01) a reduction (linear effect; P less than .01) followed by an increase (quadratic effect; P less than .05) in total PRL concentration after injection; however, when GRF was combined with TRF, such effects were not observed (P greater than .10). Results showed that 1) chronic injections of GRF for 12 wk sustained GH concentration, 2) TRF and GRF acted synergistically to elevate GH AUC, 3) TRF increased T4 concentrations throughout the 12-wk treatment period, 4) chronic TRF treatment decreased the basal PRL concentration and 5) chronic GRF + TRF treatment decreased the basal concentration of T4.     

Effects of active immunization against somatostatin (SRIF) and/or injections of growth hormone-releasing factor (GRF) during gestation on hormonal and metabolic profiles in sows.

The hormonal responses of gestating sows to immunization against somatostatin conjugated to bovine serum albumin (SRIF-IMM) and/or injections of growth hormone-releasing factor (GRF) were studied with thirty-eight second parity sows. Immunization against bovine serum albumin (BSA-IMM) was used as control. First immunizations were done on day 30 and boosters were given on days 44, 58, 72, 86 and 100 of gestation. Injections of GRF (9 mg of GRF (1-29)NH2 per injection) or saline were given at 0800, 1400 and 2000 hr daily from day 90 of gestation until parturition. Mean body weights of sows at 85 and 110 d of gestation were 196.3 and 210.5 kg, respectively (SE = 0.8). Jugular blood samples were collected from 0740 hr to 1100 hr at 20 min intervals on days 90, 101 and 112 of gestation. On day 112, additional samples were collected from 1340 hr to 1700 hr and from 2140 hr to 2300 hr. At 112 d of gestation, antibody titers against SRIF (% binding, 1:150 dilution) were higher (P less than 0.01) for SRIF-IMM (13.5%) vs BSA-IMM (0.95%) sows. There was no effect of SRIF-IMM nor was there a GRF by SRIF-IMM interaction on any variable measured (P greater than 0.05). Injections of GRF increased (P less than 0.01) the area under the curve (AUC) for growth hormone (GH; 305 vs 1623 ng/min/ml). The increase was greater as days of injection increased (P less than 0.05). Administration of GRF did not affect prolactin (Prl) AUC (P greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)