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1.
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.  相似文献   


2.
采用ELISA方法检测了3个不同体重梯度(90、110和130 kg)的川藏黑猪配套系和DLY猪血清中生长激素(GH)和生长激素释放激素(GHRH)的含量变化,并分析了其与肌纤维面积(CSA)和肌内脂肪(IMF)含量的关系。结果显示,90、110和130 kg体重梯度川藏黑猪配套系和DLY猪血清中GH含量分别为14.25、14.61、14.11及17.86、16.98、16.77 μg/L,GHRH含量分别为22.88、23.98、24.33及27.72、27.47、28.39 μg /L,除DLY猪90和130 kg血清中GH含量差异显著(P<0.05)外,品种内不同体重梯度间差异均不显著(P >0.05);不同猪种间,除110 kg梯度GHRH水平差异不显著(P >0.05)外,其余川藏黑猪配套系均显著低于DLY猪(P< 0.05)。相关性分析结果显示,GH、GHRH水平与CSA呈显著正相关(P< 0.05),与IMF含量呈极显著负相关(P< 0.01)。结果表明GH和GHRH可能通过血液对猪肌纤维的生长和肌内脂肪的沉积进行调控。  相似文献   

3.
The growth hormone (GH) and growth hormone releasing hormone (GHRH) contents in serum of 3 weights (90,110 and 130 kg) of Chuanzang Black swine hybrid and DLY pigs were detected by enzyme-linked immune sorbent assay (ELISA),their relationship with cross sectional area of muscle fiber (CSA) and intramuscular fat (IMF) content were also analyzed.The results showed that the GH contents of Chuanzang Black swine hybrid and DLY pigs of 3 weights were 14.25,14.61,14.11 and 17.86,16.98,16.77 μg/L,respectively,while the GHRH contents of which were 22.88,23.98,24.33 and 27.72,27.47,28.39 μg/L,respectively.There was no significant difference in different weight of the same breeds (P >0.05) except the significant difference between 90 and 130 kg of DLY pigs (P<0.05).The GH and GHRH contents of Chuanzang Black swine hybrid were both significant lower than DLY pigs of the same bodyweight (P< 0.05) except GHRH content of 110 kg weight (P >0.05).Relevance analysis showed that GH and GHRH contents had a significant positive correlation with CSA (P< 0.05),and an extremely significant negative correlation with IMF content (P< 0.01),which prompted that GH and GHRH might regulate the growth of muscle fiber and IMF deposition through blood.  相似文献   

4.
A combined anterior pituitary (CAP) function test was assessed in eight healthy male beagle dogs. The CAP test consisted of sequential 30-second intravenous administrations of four hypothalamic releasing hormones in the following order and doses: 1 μg of corticotropin-releasing hormone (CRH)/kg, 1 μg of growth hormone-releasing hormone (GHRH)/kg, 10 μg of gonadotropinreleasing hormone (GnRH)/kg, and 10 μg of thyrotropin-releasing hormone (TRH)/kg. Plasma samples were assayed for adrenocorticotropin, cortisol, GH, luteinizing hormone (LH), and prolactin (PRL) at multiple times for 120 min after injection. Each releasing hormone was also administered separately in the same dose to the same eight dogs in order to investigate any interactions between the releasing hormones in the combined function test.Compared with separate administration, the combined administration of these four hypothalamic releasing hormones caused no apparent inhibition or synergism with respect to the responses to CRH, GHRH, and TRH. The combined administration of these four hypothalamic releasing hormones caused a 50% attenuation in LH response compared with the LH response to single GnRH administration. The side effects of the combined test were confined to restlessness and nausea in three dogs, which disappeared within minutes after the administration of the releasing hormones. It is concluded that with the rapid sequential administration of four hypothalamic releasing hormones (CRH, GHRH, GnRH, and TRH), the adenohypophyseal responses are similar to those occurring with the single administration of these secretagogues, with the exception of the LH response, which is lower in the CAP test than after single GnRH administration.  相似文献   

5.
The effects of intravenous (IV) and intracerebroventricular (ICV) administration of either bovine growth hormone releasing hormone (GRF) or thyrotrophin releasing hormone (TRH) on plasma growth hormone (GH) and glucose levels have been examined in sheep. Intravenous GRF 1-29NH2 at 3 and 30 micrograms stimulated an increase in GH levels in a dose-dependent fashion; administration of GRF into a lateral cerebral ventricle, however, produced a smaller GH response which was similar at these two doses. Evaluation of somatostatin levels in petrosal sinus blood (which collects pituitary effluent blood) showed that ICV administration of GRF stimulated a release of somatostatin into the blood. Furthermore, concurrent administration of GRF and a potent anti-somatostatin serum ICV resulted in a much enhanced release of GH which was similar to that obtained with a comparable dose of GRF given IV. TRH (as another putative GH-secretagogue) was also administered both IV and ICV. When given IV, 200 micrograms (but not 100 micrograms) TRH produced an elevation in GH levels. By contrast, when 5 micrograms TRH was given ICV there was a decrease in circulating GH levels, but no change in plasma somatostatin concentrations. These results indicate that the smaller GH response to ICV- compared with IV-administered GRF is due to the release of somatostatin within the brain. In addition, it would seem that TRH is not a physiological GH-secretagogue in sheep.  相似文献   

6.
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  相似文献   

7.
The aim of the present study was to clarify the effects of hypothalamic dopamine (DA) on the secretion of growth hormone (GH) in goats. The GH‐releasing response to an intravenous (i.v.) injection of GH‐releasing hormone (GHRH, 0.25 μg/kg body weight (BW)) was examined after treatments to augment central DA using carbidopa (carbi, 1 mg/kg BW) and L‐dopa (1 mg/kg BW) in male and female goats under a 16‐h photoperiod (16 h light, 8 h dark) condition. GHRH significantly and rapidly stimulated the release of GH after its i.v. administration to goats (P < 0.05). The carbi and L‐dopa treatments completely suppressed GH‐releasing responses to GHRH in both male and female goats (P < 0.05). The prolactin (PRL)‐releasing response to an i.v. injection of thyrotropin‐releasing hormone (TRH, 1 μg/kg BW) was additionally examined in male goats in this study to confirm modifications to central DA concentrations. The treatments with carbi and L‐dopa significantly reduced TRH‐induced PRL release in goats (P < 0.05). These results demonstrated that hypothalamic DA was involved in the regulatory mechanisms of GH, as well as PRL secretion in goats.  相似文献   

8.
Genetic variations in plasma GH concentrations before and following thyrotropin-releasing hormone (TRH) stimulation and in IGF-I concentrations were studied in 11-mo-old Polish Friesian cattle (104 heifers and 110 bulls). A possible association between stimulated GH release, IGF-I, and the polymorphism in the GH gene causing substitution of leucine-Leu to valine-Val at amino acid position 127 of the protein was also investigated. The GH concentrations were determined in serial plasma samples collected every 15 min from 15 min before to 135 min after intravenous administration of 0.15 microg TRH/kg live weight. The analysis was performed on three variables: baseline (mean of samples at -15 and 0 min), peak (sample at 15 min after injection) and rate (peak minus sample at 60 min, divided by 45 min). The IGF-I concentrations were measured in plasma samples taken before the TRH stimulation. Additionally, first lactation records from the 75 cows earlier tested for GH release and IGF-I were used to study a possible association of milk production traits with GH genotypes. The data were analyzed by multivariate mixed linear models. The heritability of IGF-I reached a higher value (0.35) than variables baseline, peak, and rate (0.02, 0.14, and 0.14, respectively). The GH variables were positively genetically correlated with each other (0.22 to 0.93), whereas they had negative genetic correlations with IGF-I (-0.26). The Val/Val genotypes reached the highest peak value compared with other GH genotypes (P > 0.01), whereas the Leu/Leu genotypes had the highest IGF-I concentrations (P < or = 0.05). Moreover, the Leu/Val heterozygotes were superior to others in milk and protein yields, whereas the Leu/Leu homozygotes reached the highest fat yield (P > or = 0.01). We conclude that GH peak, GH rate, and IGF-I are heritable traits in young dairy cattle and are affected by the Leu/Val polymorphism in the GH gene.  相似文献   

9.
The objective of this study was to determine the effect of a subtherapeutic level of chlortetracycline (CTC) fed to growing beef steers under conditions of limited and adequate dietary protein on plasma concentrations of GH, thyroid-stimulating hormone (TSH), and thyroid hormones before and after an injection of thyrotropin-releasing hormone (TRH) + GHRH. Young beef steers (n = 32; average BW = 285 kg) were assigned to a 2x2 factorial arrangement of treatments of either a 10 or 13% crude protein diet (70% concentrate, 15% wheat straw, and 15% cottonseed hulls) and either a corn meal carrier or carrier + 350 mg of CTC daily top dressed on the diet. Steers were fed ad libitum amounts of diet for 56 d, and a jugular catheter was then placed in each steer in four groups (two steers from each treatment combination per group) during four consecutive days (one group per day). Each steer was injected via the jugular catheter with 1.0 microg/kg BW TRH + .1 microg/kg BW GHRH in 10 mL of saline at 0800. Blood samples were collected at -30, -15, 0, 5, 10, 15, 20, 30, 45, 60, 120, 240, and 360 min after releasing hormone injection. Plasma samples were analyzed for GH, TSH, thyroxine (T4), and triiodothyronine (T3). After 84 d on trial, the steers were slaughtered and the pituitary and samples of liver were collected and analyzed for 5'-deiodinase activity. Feeding CTC attenuated the GH response to releasing hormone challenge by 26% for both area under the response curve (P<.03) and peak response (P<.10). Likewise, CTC attenuated the TSH response to releasing hormone challenge for area under the response curve by 16% (P<.10) and peak response by 33% (P<.02), and attenuated the T4 response for area under the curve by 12% (P<.08) and peak response by 14% (P<.04). Type II deiodinase activity in the pituitary was 36% less (P<.02) in CTC-fed steers than in steers not fed CTC. The results of this study are interpreted to suggest that feeding subtherapeutic levels of CTC to young growing beef cattle attenuates the release of GH and TSH in response to pituitary releasing hormones, suggesting a mechanism by which CTC may influence tissue deposition in cattle.  相似文献   

10.
Thyrotropin (TSH) responses were determined in eight healthy male beagle dogs after a single administration of thyrotropin-releasing hormone (TRH) and the combined administration of four hypothalamic releasing hormones, i.e., corticotropin-releasing hormone, growth hormone-releasing hormone, gonadotropin-releasing hormone, and TRH. In both tests, TRH was administered in a dose of 10 μg/kg. Basal TSH concentrations ranged form 0.07 to 0.27 μg/1(mean ± SE, 0.14 ± 0.02 μg/1). The administration of TRH, alone or in the combined test, resulted in a prompt and significant increase in TSH with mean (±SE) plasma TSH peaks of 1.26 ± 0.22 μg/1 at 10 min and 0.85 ± 0.17 μg/1 at 30 min, respectively. The area under the curve (0–120 min) was significantly lower in the combined test than in the single TRH test, whereas the increments were not significantly different. It is concluded that measurements of TSH responses to TRH alone and in combination with other releasing hormones can be used for the assessment of pituitary thyrotropic cell function. In the combined test, the TSH response is slightly lower than that in the single test.  相似文献   

11.
Serotonin stimulates secretion of growth hormone (GH) in cattle, but the mechanism is unknown. In rats, thyrotropin-releasing hormone (TRH) mediates serotonin-induced secretion of GH. We hypothesized that the same is true in cattle. Cattle were fed for 2h daily to synchronize secretion of GH, such that concentrations of GH were high before and low after feeding. Our first objective was to determine whether or not feeding suppresses serotonin receptor agonist (quipazine) induced secretion of GH. Holstein steers were injected with quipazine (0.2 mg/kg BW) either 1 h before or 1 h after feeding. Quipazine-induced secretion of GH which did not differ in magnitude before and after feeding. If TRH mediates serotonin-induced secretion of GH, then magnitude of TRH-induced secretion of GH should not be different before and after feeding (our second objective). Sixteen meal-fed Holstein steers were injected with 0.3 microg TRH/kg BW either 1 h before or 1 h after feeding. Indeed, magnitude of TRH-induced secretion of GH before and after feeding was not different. Our third objective was to inhibit endogenous TRH with 3,5,3'-triiodothyronine (T(3)) and examine basal, GH-releasing hormone (GHRH)-, TRH- and quipazine-induced secretion of GH. Sixteen Holstein steers were injected daily with either T(3) (3 or 6 microg/kg BW) or vehicle for 20 days and then challenged sequentially with vehicle or GHRH, TRH, or quipazine. T(3) did not affect basal, GHRH- or TRH-induced secretion of GH, but reduced basal secretion of thyroxine. T(3) reduced but did not completely block quipazine-induced secretion of GH. In conclusion, TRH mediates, in part, serotonin-induced secretion of GH in cattle.  相似文献   

12.
Growth hormone (GH) secretion regularity and the effects of lighting condition and GH‐releasing hormone (GHRH) on GH release were determined in steers. First, steers were kept under 12:12 L : D conditions (light: 06.00–18.00 hours). The animals were then subjected to a 1‐h advancement in lighting on/off conditions (05.00 and 17.00 hours, respectively). Blood was sampled for 24 h at 1‐h interval on the seventh day of each condition. Second, GHRH was injected intravenously (IV) at 12.00 and 00.00 hours under 12:12 L : D and blood was sampled at 15‐min interval for 4‐h (1 h before and 3 h after the injection). Plasma GH concentrations were measured by a radioimmunoassay. Periodicity of GH secretory profile was calculated by power spectrum analysis using the maximum entropy method. Plasma GH concentrations showed a characteristic pattern consisting of four distinct peaks. Mean periodicity of GH secretory profile was 5.7 h, and it was not altered by any change in lighting conditions. IV injection of GHRH increased GH secretion during the day and night. The increase in GH secretory volume after GHRH injection during the night was equal to that during the day. The present results suggest that GH secreted from the anterior pituitary have regularity in steers.  相似文献   

13.
The aim of the current study was to investigate the effects of a porcine growth hormone releasing hormone (pGHRH) gene plasmid injection in piglets on growth performance and whole body protein turnover. Sixty male Canadian Landrace × Chinese Taihu piglets were assigned to an intramuscular injection of 0 (control), 0.25, 0.5, 1 and 2 mg. All pigs were fed with the same diet (crude protein: 239.8 g/kg, digestible energy: 14.28 MJ/kg) at ad libitum intake. Protein turnover was determined on the 22nd day with a three-pool model by using a single-dosage, end-product analysis method with 15 N-glycine as a tracer. Injection of the pGHRH gene plasmid increased the piglets' growth rate, altered feed intake and decreased feed conversion ratio. It increased plasma growth hormone releasing hormone (GHRH), growth hormone (GH), insulin-like growth factor-I (IGF-I) and somatostatin but reduced serum urea and triglyceride. It reduced the urinary nitrogen excretion and led to higher nitrogen retention as well as the efficiencies of nitrogen retention and digestible N utilization. It increased the rates of protein synthesis, protein breakdown and net protein gain. Excretion of endogenous urinary nitrogen was reduced and nitrogen reutilization rate was improved. Conclusions: Injection of the pGHRH gene plasmid in skeletal muscle stimulated GHRH, GH and IGF-I excretion in piglets. Protein deposition was increased by an increase in protein synthesis and a smaller increase in protein breakdown, which was accompanied by reducing amino acid oxidation and increasing nitrogen reutilization.  相似文献   

14.
本试验旨在研究壳聚糖对断奶仔猪生长性能、粪便评分及血清激素和T淋巴细胞亚群的影响。选取28日龄断奶的杜×大×长三元杂交仔猪60头,随机分为5组(每组12头):对照组饲喂基础饲粮,试验组分别饲喂在基础饲粮中添加250、500、1 000和2 000 mg/kg壳聚糖的试验饲粮。试验期14 d。结果表明:1)饲粮添加250~2 000 mg/kg壳聚糖显著提高断奶仔猪的平均日增重(ADG)(P0.05),显著降低料重比(F/G)(P0.05);2)饲粮添加250~2 000 mg/kg壳聚糖显著降低试验第11天断奶仔猪的粪便评分(P0.05);3)饲粮添加适宜剂量的壳聚糖显著提高断奶仔猪的血清促生长激素释放激素(GHRH)(250~2 000 mg/kg)、生长激素(GH)(500~1 000 mg/kg)和瘦素(LP)(2 000 mg/kg)的浓度(P0.05),显著降低血清促肾上腺皮质激素释放激素(CRH)(250~2 000 mg/kg)、促肾上腺皮质激素(ACTH)(500~1 000 mg/kg)、皮质醇(COR)(250~2 000 mg/kg)和可溶性CD8(sCD8)(500~2 000 mg/kg)的浓度(P0.05)。由此可见,饲粮中添加适宜剂量的壳聚糖能够促进断奶仔猪的生长,降低腹泻,缓解断奶应激。  相似文献   

15.
Tumor necrosis factor (TNF)‐α is a powerful macrophage cytokine released during infection, circulating in the blood to produce diverse effects in the organism. We examined the effect of recombinant bovine TNF‐α (rbTNF‐α) administration on hormone release in dairy cows during early lactation. Twelve non‐pregnant Holstein cows were treated subcutaneously with rbTNF‐α (2.5 µg/kg) or saline twice (at 11.00 and 23.00 hours). At 11.00 hours the next day, the cows were given growth hormone‐releasing hormone (GHRH, 0.25 µg/kg), thyrotrophin‐releasing hormone (TRH, 1.0 µg/kg), thyroid‐stimulating hormone (TSH, 10 µg/kg) or adrenocorticotropic hormone (500 µg/head) via the jugular vein. In the growth hormone‐releasing hormone challenge, the plasma growth hormone concentration was lower in the rbTNF‐α group than in the control (saline) group. The growth hormone and TSH responses to TRH were also smaller in the rbTNF‐α group than in the control. The plasma prolactin response to TRH was not affected by the rbTNF‐α treatment. In the TSH challenge, the rbTNF‐α‐treated cows had lower responses, as measured by plasma triiodothyronine and thyroxine, than the control cows. The rbTNF‐α treatment produced an increase in the basal plasma cortisol level, but the cortisol response to adrenocorticotropic hormone was the same level in both groups. The plasma concentrations of TNF‐α and interleukin‐1β in the cows were elevated by the rbTNF‐α treatment. The milk yield was reduced by the rbTNF‐α administration during 4 days. These data demonstrate that TNF‐α alters the secretion of pituitary and thyroid hormones in lactating cows. This effect may contribute to the suppression of the lactogenic function of the mammary gland observed in cases of coliform mastitis with high circulating TNF‐α levels.  相似文献   

16.
Abstract

Genetic variation in plasma growth hormone (GH) concentration before and after GRF (growth hormone releasing factor) stimulation was studied in young bulls (N=284) and heifers (N=212), the progeny of 53 sires of four dairy and dual-purpose breeds (Danish Jersey, Red Dane, Danish Friesian and Danish Red and White). Male and female calves were reared, fed and tested on separate experimental stations; thus sex, station and feeding were completely confounded effects. The animals were tested at about 9 months of age, after a 24 h fast. GH concentration was measured in serial plasma samples collected for 1 h before and 1 h following intravenous administration of 2.0 ug synthetic GRF(1–29)NH2/kg live weight>0.75. Prior to statistical analysis, concentrations were loge-transformed. Response variables were BASELINE (mean GH in -15, -5 and 0 min samples) and PEAK (mean GH in 10, 15 and 20 min samples). A statistical model taking at least three generations of ancestral relationships into account was used to estimate variance and covariance components for traits in male and female calves by use of restricted maximum likelihood methods.

Heritability of BASELINE was low (0.04 ± 0.12) in males but high in females (0.60 ± 0.16). The heritability of PEAK was high in both sexes (males, 0.42 ± 0.16; females, 0.60 ± 0.16). Genetic correlations between the same trait measured in males and females were low for BASELINE (r g = 0.32±0.55) but high for PEAK (r g = 0.82±0.15). Within sex, BASELINE and PEAK were both highly genetically correlated (males, r g=0.62 ± 0.40; females, r g= 1.00 ± 0.07).

We conclude that growth hormone concentration is a highly heritable trait in juvenile cattle of both sexes, and that GRF stimulation is benificial to the uncovering of genetic differences among animals.  相似文献   

17.
The effect of pituitary adenylate cyclase-activating polypeptide (PACAP) on growth hormone (GH) release was compared with that of prostaglandin E2 (PGE2) and growth hormone releasing factor (GRF) from cultured bovine anterior pituitary cells in vitro. Both PACAP and PGE2 stimulated GH release at concentrations as low as 10−9 and 10−8 M, respectively, (P<0.01). However, GRF released GH at a concentration as low as 10−13 M (P<0.01). Percent increases of GH compared with controls were not significantly different among GRF, PACAP, and PGE2 at 10−7 M; however, the increases of GH by the 10−8 M GRF, PACAP and PGE2 were 196, 118, and 27%, respectively, (P<0.01), and 124, 65, and 1% in the 10−9 M media, respectively, (P<0.01). When GRF and somatostatin (SS) were added together, the GH releasing effect of GRF was blunted (P<0.01). Similar bluntness were observed in PACAP and PGE2, when SS was added. The stimulatory effects of GRF and PGE2 together were similar to that by either GRF or PGE2 alone. When GRF and PACAP were added together, the GH released by both secretagogues was greater than that by PACAP alone (P<0.01); however, a synergistic effect was not clear when compared with GRF alone.

These findings suggest that PACAP and PGE2 may modulate the release of GH in cattle.  相似文献   


18.
试验研究注射促生长激素释放肽(GHRP-2)对雅南猪生产性能、胴体性状和血液生化指标的影响。试验采用单因子试验设计,试验组隔天肌肉注射20μg/kg BW GHRP-2,对照组隔天注射同等剂量的生理盐水。试验期为4周。结果表明:与对照组相比,注射20μg/kgBW GHRP-2显著提高了蛋白质的消化利用率和血清中总蛋白的水平;有提高日增重、饲料转化率的趋势,但不影响日采食量;对猪胴体性状没有明显影响。  相似文献   

19.
To determine whether long-term administration of growth hormone (GH)-releasing factor (GRF) and(or) thyrotropin-releasing hormone (TRH) alters ovarian follicular fluid (FFL) concentrations of insulin-like growth factor-I (IGF-I), progesterone, and estradiol (E2), and follicular growth, Friesian x Hereford heifers (n = 47; 346 +/- 3 kg) were divided into the following four groups: control (vehicle; n = 11); 1 micrograms GRF (human [Des NH2 Tyr1, D-Ala2, Ala15] GRF [1-29]-NH2).kg-1 BW.d-1 (n = 12); 1 microgram TRH.kg-1 BW.d-1 (n = 12); or GRF + TRH (n = 12). Daily injections (s.c.) continued for 86 d. On d 89, heifers that had been synchronized were slaughtered and ovaries were removed. Follicles were grouped by magnitude of diameter into the three following sizes: 1 to 3.9 mm (small, n = 55), 4.0 to 7.9 mm (medium, n = 63), and greater than or equal to 8 mm (large, n = 71). Growth hormone-releasing factor and(or) TRH did not affect (P greater than .10) IGF-I concentrations in FFL of any follicle size group. Growth hormone-releasing factor increased (P less than .06) size (means +/- pooled SE) of large follicles (14.7 vs 13.0 +/- .6 mm). Growth hormone-releasing factor also increased (P less than .05) progesterone concentrations 4.4-fold above controls in FFL of medium-sized follicles but had no effect on progesterone in FFL of the small or large follicles. Thyrotropin-releasing hormone did not alter FFL progesterone or E2 concentrations in any follicle size group. We conclude that the GRF and(or) TRH treatments we employed did not affect intra-ovarian IGF-I concentrations, but GRF may alter steroidogenesis of medium-sized follicles and growth of large follicles.  相似文献   

20.
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