Bone marrow adipocytes: a neglected target tissue for growth hormone

Bone marrow (BM) contains numerous adipocytes. These share a common precursor with osteoblasts and chondrocytes, but their function is unknown. It is unclear what regulates the differentiation of these three different cell types, though their subsequent metabolic activity is under hormonal regulation. GH and estrogen stimulate bone growth and mineralization, by direct effects on chondrocytes and osteoblasts. GH also stimulates lipolysis in subcutaneous and visceral adipocytes. However, adipocytes in BM have largely been ignored as potential targets for GH or estrogen action. We have addressed this by measuring BM adipocyte number, perimeter and area as well as bone area and osteoblast activity in GH-deficient dwarf (dw/dw), normal, or ovariectomized (Ovx) rats, with or without GH, IGF-1, PTH, or estrogen treatment or high fat feeding. Marrow adipocyte numbers were increased 5-fold (P < 0.001) in dw/dw rats, and cell size was also increased by 20%. These values returned toward normal in dw/dw rats given GH but not when given IGF-1. Cancellous bone area and osteoblast number were significantly (P < 0.005) lower in dw/dw rats, though alkaline phosphatase (ALP) activity in individual osteoblasts was unchanged. GH treatment increased % osteoblast covered bone surface without affecting individual cell ALP activity. Ovariectomy in normal or dw/dw rats had no affect on marrow adipocyte number nor size, although estrogen treatment in ovariectomized (Ovx) normal rats did increase adipocyte number. Ovx decreased tibial cancellous bone area in normal rats (64%; P < 0.05) and decreased osteoblast ALP-activity (P < 0.01) but did not affect the percentage of osteoblast-covered bone surface. Estrogen replacement reversed these changes. While treatment with PTH by continuous sc infusion decreased cancellous bone (P < 0.05) and high fat feeding increased the size of BM adipocytes (P < 0.01), they did not affect BM adipocyte number. These results suggest that GH has a specific action on BM adipocytes that is not simply due to altered bone or fat metabolism. We conclude that the marrow adipocyte lineage is an important and specific target for GH action. The inverse relationship between adipocyte number and osteoblast covered bone surface, together with the well-known effects of GH on epiphysial chondrocytes leads us to propose that GH plays two important roles on cells of all three lineages. During differentiation, it regulates the numbers of each cell type that are maintained from the common precursor lineage. Subsequently it has cell-specific effects on the metabolic activities of the differentiated cells. In the case of marrow adipocytes, GH-dependent lipolysis could provide an important hormonally regulated local high energy source in bone.     

Mechanism of action of estrogen on intramembranous bone formation: regulation of osteoblast differentiation and activity.

Dynamic bone histomorphometry, [3H]thymidine radioautography, and Northern analysis for bone matrix proteins and insulin-like growth factor-I (IGF-I) were performed in calvariae of ovariectomized (OVX) and estrogen-treated OVX rats. Treatment of OVX rats with diethylstilbestrol (DES) for 2 weeks reduced the periosteal mineral apposition rate, osteoblast number, and osteoblast size in calvarial periosteum. DES treatment also reduced the number of preosteoblasts in the S phase of the cell cycle, suggesting that the decrease in osteoblast number was due in part to inhibition of proliferation of osteoprogenitor cells. One week after ovariectomy, there were small increases in mRNA levels for pre pro-alpha 2 (I) subunit of type I collagen (collagen), osteocalcin, and osteonectin and a large increase in the mRNA level for IGF-I. DES treatment resulted in rapid decreases (3 h) in the mRNA levels for osteonectin, osteocalcin, and IGF-I. In contrast, mRNA levels for collagen were virtually unchanged after short term DES treatment. Uterus and liver served as positive and negative control tissues, respectively, for the effects of DES on IGF-I mRNA levels in OVX rats; mRNA levels were increased in uterus and decreased in liver after hormone treatment. We conclude from these studies that estrogen reduces periosteal bone formation by inhibiting both the differentiation and activity of osteoblasts. Furthermore, down-regulation of mRNA levels for IGF-I and bone matrix proteins precedes the changes in dynamic bone histomorphometry.     

淫羊藿总黄酮对去卵巢大鼠骨髓间充质干细胞成骨和成脂分化中DKK1蛋白动态表达的影响

目的观察DKK1在淫羊藿总黄酮调控去势雌性大鼠骨髓间充质干细胞成骨和成脂分化平衡过程中的动态表达,为进一步阐明淫羊藿总黄酮治疗绝经后骨质疏松症的作用机制提供实验依据。方法体外分离培养去势雌性大鼠来源骨髓间充质干细胞,分别在成骨诱导液和脂肪诱导液条件下连续培养15 d,并在此基础上添加剂量为10μg/mL的淫羊藿总黄酮。采用ALP染色、ALP活性测定、油红O染色以及荧光定量PCR技术,观察淫羊藿总黄酮对骨髓间充质干细胞成骨和成脂分化的影响。用酶联免疫法(ELISA)检测淫羊藿总黄酮处理过程中DKK1蛋白的动态表达,观察DKK1蛋白在淫羊藿总黄酮调控去势雌性大鼠骨髓间充质干细胞成骨和成脂分化平衡过程中的作用。结果淫羊藿总黄酮能显著增加骨髓间充质干细胞ALP的表达以及成骨早期分化因子Runx2 mRNA的表达,显著下调骨髓间充质干细胞中脂肪形成关键基因PPARγ-2mRNA的表达,从而抑制脂滴的形成。在成骨诱导条件下,EFs呈时间依赖性下调DKK1的表达;在脂肪诱导条件下,EFs呈时间依赖性抑制DKK1蛋白的上调。结论通过抑制DKK1蛋白的表达调控去势雌性大鼠BMSCs成骨和成脂分化平衡,可能是淫羊藿总黄酮治疗绝经后骨质疏松症的分子机制之一。     

去卵巢大鼠骨形成参数和血清碱性磷酸酶的相关性研究

目的　观察去卵巢大鼠骨组织形态计量学参数和血清碱性磷酸酶 (ALP)之间的相关性。方法　 4个半月龄 SD大鼠双侧卵巢去除术后预防用药 90 d。用骨组织形态计量学方法测定大鼠胫骨组织近端松质骨形态计量学参数 ,并测定血清 ALP含量。结果　去卵巢组大鼠血清 ALP含量增加 ,骨形成参数增加 (P<0 .0 5)。去卵巢组和预防用药组骨形成参数与 ALP测量值之间有相关性 (P<0 .0 5)。去卵巢组的骨组织形态计量学参数与 ALP测量值之间的相关系数大于预防用药组。结论　去卵巢大鼠血清 ALP与骨形成参数之间存在相关性 ,这种相关性在给药后下降。     

Modulation of the prolactin response to thyrotropin releasing hormone by ovarian steroids in ovariectomized turkeys (Meleagris gallopavo)

The effect of thyrotropin releasing hormone (TRH) administered intramuscularly (im) on serum levels of prolactin (Prl) in ovariectomized (ovx) adult turkeys before and following the onset of photostimulation, before and during daily administration (im) of progesterone (P; 0.1, 0.4, or 1.0 mg/kg), estradiol benzoate (EB; 0.01, 0.1, or 0.2 mg/kg), or their combination (1.0 mg/kg EB + 0.1 mg/kg P) were studied. Ovariectomy reduced Prl levels in the serum of photostimulated turkeys, and blunted the Prl response to TRH administration. Progesterone treatment had no effect on basal serum Prl levels but the Prl response to TRH was higher in P-treated turkeys than in non-treated ovx turkeys. Basal serum Prl levels were higher (P less than 0.05) in the EB-treated ovx turkeys than in the untreated birds. The Prl response to TRH in ovx EB-treated turkeys was greatly increased (P less than 0.05). Progesterone treatment of EB-primed ovx turkey did not alter the basal levels of serum Prl or the Prl response to TRH administration. These results suggest that ovarian steroids may be responsible for the increased Prl secretion in the female turkey associated with laying.     

A decrease in opioid tone amplifies the luteinizing hormone surge in estrogen-treated ovariectomized rats: comparisons with progesterone effects

It is well known that the estrogen-induced LH surge in ovariectomized (ovx) rats is invariably far less in magnitude than the preovulatory LH surge or that induced by progesterone (P) in estrogen-primed ovx rats. Recent studies show that a decrease in hypothalamic inhibitory opioid tone by the neural clock (NC) is responsible for the induction of the preovulatory LH surge on proestrus. Therefore, we hypothesized that the diminished LH response in estrogen-treated ovx rats may be due to an inadequate reduction in opioid tone. To test this hypothesis the effects of transiently decreasing the opioid tone with an opiate receptor antagonist, naloxone (NAL), on LH secretion in estrogen-primed, short term (5 days) and long term (4 weeks) ovx rats were examined. NAL (2 mg/h) was infused iv from 1100-1400 h on day 2 in rats receiving either sc implants (two, 15 mm each) filled with 17 beta-estradiol (300 micrograms/ml in oil) or sc estradiol benzoate (EB; 10 micrograms/rat) injections at 1000 h on day 0. For comparison of NAL- and P-induced LH responses, EB-primed short and long term ovx rats received P injection (2 mg/rat, sc) instead of NAL infusion at 1100 h. Estrogen treatment alone induced a spontaneous rise in plasma LH on the afternoon of day 2, with peak LH levels ranging between 1.5-2.4 ng/ml. NAL infusion markedly enhanced the LH surge in both groups of ovx rats. In short term ovx rats NAL-induced peak LH levels (5-6 ng/ml) were less than those observed in rats receiving supplemental P treatment or that observed previously on proestrus (10-15 ng/ml). However, in long term EB-primed ovx rats, NAL infusion evoked LH surges equivalent to those observed after P injection. In addition, analysis of the episodic LH secretion pattern showed that NAL infusion accelerated the frequency and amplitude of LH discharge and significantly changed the contour of LH episodes. These results show that a transient decrease in inhibitory opioid tone before a spontaneous LH rise in estrogen-treated ovx rats can accelerate episodic LH secretion to culminate in LH surges that resemble those induced by P and the preovulatory LH surge. Therefore, these observations are in accord with the view that the NC-induced curtailment in the inhibitory opioid tone may be inadequate in estrogen-treated rats; NAL infusion and P treatment intensify decrements in inhibitory opioid tone to reinstate the preovulatory-type LH surge in these rats.     

葛根素对去卵巢大鼠机体骨代谢影响的观察

目的 观察葛根素对去卵巢大鼠机体骨代谢的影响,探讨其对雌激素缺乏引起的骨质疏松症的治疗作用.方法 3月龄清洁级SD大鼠60只,背驮式切除双侧卵巢后每日灌胃葛根素5 mg/kg(P-5组),10 mg/kg(P-10组)和20 mg/kg(P-20组),并设假手术组(Sham),模型组(OVX)和己烯雌酚阳性对照组(E).3个月后处死动物,测定大鼠胫骨干重、灰分重量和矿物质含量,胫骨Ca、P含量以及血清相关骨代谢指标.结果 与OVX组相比,葛根素各组的胫骨矿物质含量(mg/g)均有增加(574±17,590±22和597±18),其中P-20组差异显著(P＜0.05);葛根素各组的胫骨Ca含量(mg/g)高于OVX组 (132±10,222±7,228±8),其中P-10,P-20两组差异显著(P＜0.05,P＜0.01),说明服用葛根素后大鼠骨量得到增加;同时,葛根素各组的碱性磷酸酶(U/L)与OVX组有所降低(101±26,90±20,71±15),其中P-10,P-20两组差异显著(P＜0.05,P＜0.01),说明去卵巢大鼠骨的高转换状态得到改善.结论 葛根素能抑制去卵巢大鼠骨量的丢失,对骨代谢有较好的调节作用,对雌激素缺乏引起的骨质疏松症有一定的治疗作用.     

温和灸对去卵巢大鼠股骨I型胶原表达的影响及意义

目的观察去卵巢大鼠骨I型胶原表达变化及温和灸、苯甲酸雌二醇注射液（BE2）的干预效果,探讨“补虚化瘀”灸法治疗绝经后骨质疏松症（PMO）的机制。方法将50只8月龄雌性Wistar大鼠随机分为假手术组10只和去势组40只,后者行双侧卵巢切除术,并于90d后随机分为模型组、雌激素组、艾灸组和艾灸＋雌激素组各10只,其后假手术组和模型组正常饲养,雌激素组予BE2后肢肌肉注射、艾灸组按“补虚化瘀法”取穴行温和灸治疗,艾灸＋雌激素组同时给予BE2注射和艾灸治疗。疗程结合后处死大鼠,分别以免疫组化法和原位杂交法检测右股骨I型胶原mRNA表达。结果模型组大鼠右股骨I型胶原蛋白及mRNA表达均明显低于假手术组及各治疗组,各治疗组中仅艾灸＋雌激素组mRNA表达阳性反应面积明显大于艾灸组（P〈0．05或0．01）,余各指标比较无显著差异。结论温和灸可明显增强去卵巢大鼠股骨I型胶原表达（效果与BE2相似）,此可能为“补虚化瘀”灸法治疗PMO的机制之一。     

IGF-1对去卵巢大鼠骨密度及骨力学强度的影响

目的 研究外源性胰岛素样生长因子-1(IGF-1)对去卵巢(OVX)骨质疏松大鼠骨密度、骨转换率、骨力学强度等方面的影响.方法 对大鼠施行双侧卵巢摘除术,术后3个月以骨密度测定证实骨质疏松的存在后,随机分为5组,分别以生理盐水、甲状旁腺激素1-34及3种不同剂量IGF-1进行干预.同时设立生理盐水干预的假手术大鼠作为对照.8周后检测血清钙、磷、骨钙素水平及碱性磷酸酶活性;测定腰椎骨密度、股骨力学强度;组织学染色测定股骨远端骨皮质厚度.结果 IGF-1虽未提高OVX大鼠腰椎骨密度却可以显著提高其股骨力学强度.血清学检测结果表明,IGF-1可降低血清钙、磷、骨钙素水平及碱性磷酸酶活性;组织学染色显示IGF-1可显著提高OVX大鼠股骨骨皮质厚度.结论 IGF-1可增加OVX大鼠股骨的力学强度,此作用可能是通过改善骨结构而非提高骨密度所实现的.     

去卵巢大鼠骨质疏松凋亡细胞及其相关因素观察

目的　探讨去卵巢大鼠骨细胞凋亡活性及其相关因素。方法　采用3′-OH末端DNA原位标记技术观察凋亡细胞活性;采用免疫组化SABC法观察bcl-2、Fas、转化生长因子（TGF）β1的表达情况。结果　去卵巢大鼠成骨细胞的凋亡细胞活性为（40.5±5.2）%,较假手术组(24.5±3.0)%与去卵巢+尼尔雌醇/左炔诺孕酮治疗组［OVX+N/L组,（26.4±2.9)%］明显增加,差异有显著性(P＜0.01);去卵巢大鼠破骨细胞的凋亡细胞活性为（8.4±1.2）%,明显低于假手术组(24.0±2.9)%与OVX+N/L组(26.5±3.1)%,差异具有显著性(P＜0.01)。3组成骨细胞与破骨细胞内bcl-2阳性表达率均较低,差异无显著性(P值均>0.05);去卵巢大鼠组成骨细胞内Fas(80.0%)高于假手术组（40.0%）和OVX+N/L组（40.0%）,而破骨细胞内Fas(20.0%)低于假手术组(70.0%)和OVX+N/L组(73.3%),后者差异有显著性(χ2=7.94,P＜0.05),OVX组成骨和破骨细胞内TGFβ1(分别为20.0%、0),均低于其他两组,前者差异有极显著意义(χ2=13.104,P＜0.01)。结论　去卵巢大鼠骨丢失主要是由于雌激素水平低下引起破骨细胞凋亡减少、成骨细胞凋亡活性增加致骨吸收功能明显增加而超过骨形成所致;TGFβ1的分泌可能需要雌激素的刺激,TGFβ1表达可能抑制成骨细胞凋亡,促进破骨细胞凋亡,Fas可能诱导破骨细胞凋亡。     

叶酸对去卵巢大鼠骨质疏松的保护作用

目的 探讨叶酸对去卵巢大鼠骨质疏松的保护作用.方法 40只3月龄雌性SD大鼠随机分为5组:假手术组、去卵巢组、乙烯雌酚组(乙烯雌酚0.03 mg·kg-1·d-1)、低剂量叶酸组(叶酸5 mg·kg-1·d-1)、高剂量叶酸组(叶酸20 mg·kg-1·d-1).各组大鼠于术后1周开始灌胃给药,治疗10周,假手术组和去卵巢组给予溶媒灌胃.测定大鼠血浆总同型半胱氨酸(tHcy)浓度,骨匀浆中碱性磷酸酶(ALP)和抗酒石酸酸性磷酸酶(TRACP)的水平;取右股骨和腰5椎体进行骨密度和骨生物力学测定,取腰6椎体和左股骨制备HE切片,观察骨组织的形态学变化.结果 与假手术组比较,去卵巢大鼠血浆tHcy浓度明显升高,腰椎和股骨骨密度显著减低(均P＜0.01),血浆tHcy浓度与腰椎骨密度呈负相关(r=-0.359,P=0.040).叶酸显著降低去卵巢大鼠血浆tHcy浓度(均P＜0.01).大剂量叶酸显著增加去卵巢大鼠骨匀浆ALP水平,降低TRACP水平,增加腰椎和股骨骨密度(均P＜0.01),改善腰椎和股骨的生物力学性能.结论 去卵巢大鼠存在高同型半胱氨酸血症,高同型半胱氨酸参与了去卵巢大鼠骨质疏松的发生.叶酸对去卵巢大鼠骨质疏松具有保护作用,其机制可能与改善同型半胱氨酸的代谢作用有关.

Abstract：

Objective To investigate the protective effect of folic acid(FA) on osteoporosis in ovariectomized(OVX) rats.Methods Forty three-month-old female SD Rats were divided into 5 groups, sham operation group, OVX group, diethylstilbestrol group(0.03mg·kg-1·d-1),low dose FA Group (5 mg·kg-1·d-1),and high dose FA group (20 mg·kg-1·d-1).Gastric gavage in each group was started from one week after being ovariectomized and lasted 10 weeks. Sham operation group and OVX group were treated with solvent. The rats were sacrificed at the end of 10th week after treatment. The total homocysteine(tHcy) in plasma, alkaline phosphatase(ALP), and tartrate-resistant acid phosphatase(TRACP) activity of bone homogenates were measured. The bone mineral density(BMD) and bone biomechanics were determined using L5 vertebrae and right femur. The bone tissue slices were made with L6 vertebrae and left femur and HE stained, and then the histomorphology was observed. Results Compared with sham operation group, plasma tHcy level was significantly increased(P＜0.01), BMD of lumbar vertebrae and femur was remarkedly decreased in OVX group(all P＜0.01). Plasma tHcy concentration was negatively correlated with lumbar BMD(r=-0.359, P=0.040). Plasma tHcy level in both groups treated with folic acid was significantly reduced(all P＜0.01). The ALP concentration in bone homogenates was higher, the TRACP concentration in bone homogenates was lower, and BMD and bone biomechanics of lumbar vertebrae and femur were increased in high dose FA group than those in OVX group(all P ＜0.01). Conclusions In OVX rats hyperhomocysteinemia existed and was involved in the development of osteoporosis. Folic acid could protect OVX rats from osteoporosis, due probably to improved homocysteine metabolism.     

MT1-MMP、MMP-2和TIMP-2基因在去卵巢大鼠成骨细胞中的表达

目的　通过观察去卵巢 (OVX)骨质疏松模型大鼠成骨细胞膜型基质金属蛋白酶 1(MT1 MMP)基因的表达 ,探讨绝经后骨质疏松的发病机制。　方法　对OVX大鼠与假手术大鼠进行骨密度和骨组织形态计量学测定。股骨远端行原位杂交检测骨组织MT1 MMP、MMP 2和TIMP 2mRNA表达 ,免疫组化检测骨组织MT1 MMP、MMP 2和TIMP 2蛋白质表达。　结果　OVX大鼠第 3、4腰椎骨密度 (0 14 4± 0 0 11) g cm2 、(0 14 3± 0 0 15 ) g cm2 较对照组 (0 15 8± 0 0 18)g cm2 、(0 16 2± 0 0 17) g cm2 明显减少 ,OVX组骨小梁面积 (9 5 8± 3 39) %、厚度 (40 85± 8 0 4 ) μm和数目 (2 30± 0 4 8)个 mm分别较对照组 (2 0 6 3± 4 8) %、(44 73± 6 8) μm、(4 6± 0 7)个 mm明显下降 ,OVX组骨小梁间隔 (5 85 8± 115 1) μm较对照组 (2 5 4 6± 4 8 0 ) μm明显增宽 ;成骨细胞MT1 MMPmRNA与蛋白质表达下调 ,而MMP 2和TIMP 2之间表达无差异。　结论　雌激素不足可使成骨细胞MT1 MMP基因表达减少 ,可能为绝经后骨质疏松的发病机制之一。     

Gonadotropin gene expression and secretion in gonadotropin-releasing hormone antagonist-treated male rats: effect of sex steroid replacement.

The possibility of direct pituitary effects of sex steroids on gonadotropin gene expression and synthesis was studied in male rats. The animals were treated with a potent GnRH antagonist, Ac-D-pClPhe-D-pClPhe-D-Trp-Ser-Tyr-D-Arg-Leu-Arg-Pro-D-Ala-+ ++NH2CH3COOH (Org 30276; 0.5 mg/kg BW, sc, twice daily) for 10 days. Groups of the antagonist-treated rats were implanted at the beginning of the injections with Silastic capsules containing testosterone (T), 5 alpha-dihydrotestosterone (DHT), or diethylstilbestrol (DES). Groups treated with the antagonist alone or vehicle served as controls. The antagonist treatment decreased unoccupied pituitary receptors of GnRH by 93% (P less than 0.001), serum LH by 34% (P less than 0.01), and serum FSH by 30% (P less than 0.05), and serum T became undetectable (less than 0.10 nmol/liter). Compared to antagonist treatment alone, no further effects on serum or pituitary LH levels found after steroid replacements. In contrast, the antagonist-induced decreases in serum and pituitary FSH (30% and 70%, respectively; P less than 0.05-0.01) were totally reversed by the T and DHT implants, but not by DES. Pituitary levels of the LH beta-subunit mRNA were decreased by 60% (P less than 0.01) after antagonist treatment. Combination treatment with androgens had no further effect on this mRNA, whereas DES partially reversed this suppression (P less than 0.05). In contrast, the pituitary mRNA level of the FSH beta-subunit, which decreased with antagonist treatment by 90% (P less than 0.01), returned to the control level with T and DHT replacements, but only partially with DES. The pituitary mRNA level of the common alpha-subunit was significantly suppressed only by combined antagonist plus DHT treatment (P less than 0.01). However, combination of DES with the antagonist increased alpha-subunit mRNA levels 2.4-fold (P less than 0.05) compared to antagonist treatment alone. It is concluded that the suppression of gonadotropin secretion by GnRH antagonist treatment is accompanied in male rats by a parallel reduction in mRNA levels of the gonadotropin beta-subunits. Sex steroid replacement of the antagonist-treated animals selectively reverses some of the mRNA changes. Androgens (T and DHT) increase the mRNA of FSH beta-subunit, but have no effect on the LH beta-subunit. Estrogen increases the mRNA levels of common alpha- and LH beta-subunits and slightly increases that of FSH beta.(ABSTRACT TRUNCATED AT 400 WORDS)     

氟对大鼠成骨细胞纤连蛋白表达的影响

目的 观察纤连蛋白(fibronectin)在氟中毒大鼠骨组织和体外培养成骨细胞中的表达,探讨纤连蛋白在氟骨症发生机制中的作用.方法 Wistar大鼠144只,雌雄各半,体质量约120 g,按体质量将大鼠分为4组:对照组(正常食料)、加氟(F-)组(正常食料+ 100 mg/L F-)、低钙偏食组(合成食料)、低钙偏食加氟组(合成食料+ 100 mg/L F-),每组36只,在喂养4、8个月时分别处死大鼠,取股骨组织固定、石蜡包埋;采用细胞培养的方法,体外培养乳鼠颅骨成骨细胞,按不同的染氟剂量分为4组:0(对照)、1、2、4 mg/L组,分别在培养47、72 h收集颅骨成骨细胞和培养上清.体外培养乳鼠颅骨成骨细胞,按不同的染氟剂量分为4组:0(对照)、0.01、1.00、10.00 mg/L组,在染氟培养的第2天加入矿化诱导液,继续培养3周后取出玻片、酒精固定.免疫组化(IHC)法检查纤连蛋白在大鼠股骨组织中的表达;原位杂交法测定大鼠股骨组织中纤连蛋白mRNA表达;酶联免疫吸附(ELISA)法测定颅骨成骨细胞培养液中纤连蛋白含量;RT-PCR法测定成骨细胞纤连蛋白mRNA表达;0.1％茜素红染色,光镜下观察颅骨成骨细胞矿化结节形成.结果 光镜下对照组和低钙偏食组大鼠股骨组织中纤连蛋白均有阳性表达,可见到棕黄色颗粒,但量较少;加氟组和低钙加氟组骨组织中可见到大量的纤连蛋白阳性表达的棕黄色颗粒.光镜下大鼠股骨组织中成骨细胞、骨细胞和骨髓内细胞均有纤连蛋白mRNA阳性表达,对照组和低钙偏食组纤连蛋白mRNA阳性表达的红色颗粒较少,加氟组和低钙偏食加氟组纤连蛋白mRNA阳性表达的红色颗粒较多.培养48 h,成骨细胞培养上清液中纤连蛋白均增加,4 mg/L组纤连蛋白(0.108±0.042)明显高于对照组(0.081±0.010,t=0.764,P＜0.05);培养72 h,1、2、4 mg/L组纤连蛋白(0.089±0.010、0.087±0.012、0.098±0.023)明显高于对照组(0.070±0.014,t值分别为0.765、0.704、0.996,P均＜ 0.05).培养48和72 h,1、2、4 mg/L组成骨细胞纤连蛋白mRNA表达(0.61±0.06、0.77±0.07、0.77±0.07)和(1.61±0.14、2.54±0.20、2.75±0.22)均明显高于对照组[0.48±0.04(t值分别为0.111、0.182、0.182,P均＜ 0.05)和0.97±0.08(t值分别为0.093、0.109、0.108,P均＜0.05)].在1.00、10.00 mg/L组,光镜下成骨细胞中可见大量矿化结节形成.结论 纤连蛋白在氟中毒大鼠骨组织和体外培养成骨细胞中的表达均增加,染氟也促进成骨细胞形成矿化结节,提示纤连蛋白可能通过调节骨组织的矿化过程,在氟骨症发生机制中发挥作用.     

Inhibitory effect of androgen on estrogen-induced prolactin messenger ribonucleic acid accumulation in the male rat anterior pituitary gland

Estrogens are known to exert specific stimulatory effects on basal and dopamine-inhibited PRL secretion and synthesis as well as on PRL gene expression. However, dihydrotestosterone (DHT) and progesterone (P), although inactive alone, can reverse the effect of 17 beta-estradiol (E2) on PRL release both in vivo and in vitro. Using castrated male rats, we have studied the effect of E2 (0.25 micrograms), P (2 mg), or DHT (100 micrograms) administered twice daily for 14 days alone or in combination on pituitary PRL mRNA levels measured by quantitative in situ hybridization. Treatment with E2 increased the accumulation of PRL mRNA by about 2.6-fold. Administration of P or DHT alone failed to modify PRL mRNA concentrations. However, DHT could prevent by 80% the stimulatory effect of E2 on PRL mRNA levels. Similar results were obtained by dot blot hybridization assay. The effects of sex steroids on PRL mRNA were closely paralleled to pituitary PRL content measured by RIA. The present data demonstrate that the effect of sex steroids on immunodetectable PRL result from a modulation of PRL mRNA accumulation. The sexual dimorphism observed in pituitary PRL content results from a 3.5-fold greater accumulation of PRL mRNA in intact females than in male rats. These results also clearly show that quantitative in situ hybridization is a powerful tool in the investigation of the regulation of gene expression in addition to providing valuable information on the localization of specific mRNA.     

去卵巢大鼠血清乳铁蛋白与骨密度的相关性研究

目的 探讨去卵巢大鼠血清乳铁蛋白(LF)水平与骨密度(BMD)的关系,为临床应用乳铁蛋白提供实验依据.方法 采用4月龄Wistar雌性大鼠,随机分为假手术组(sham,20只)与去卵巢模型组(ovariectomy,OVX,40只,分为OVX I组与OVX Ⅱ组,各20只),分别于术后14与18周处死OVX I组与OV...     

Multihormonal control of pre-pro-somatostatin mRNA levels in the periventricular nucleus of the male and female rat hypothalamus

The influence of sex steroids as well as the possible involvement of dopaminergic pathways in the modulation of pre-pro-somatostatin (SS) mRNA levels was investigated by quantitative in situ hybridization in the hypothalamic periventricular nucleus (PeN) in adult male and female rats. In situ hybridization was performed using a [35S]-labeled cDNA probe encoding pre-proSS mRNA. Gonadectomy performed 14 days earlier decreased the mean number of silver grains/neuron corresponding to the relative pre-proSS mRNA levels by 22% in male and by 18-28% in female rats. A 14-day treatment with the nonaromatizable androgen dihydrotestosterone (DHT) increased the mean number of silver grains/neuron by 34-40% in gonadectomized animals of both sexes. Moreover, administration of 17 beta-estradiol (E2, 0.25 microgram twice daily) increased pre-proSS mRNA levels by 40% in ovariectomized (OVX) animals. Such treatment with E2 or DHT changed the frequency distribution profile of the hybridization signal intensity, thus increasing the percentage of highly labeled neurons (greater than or equal to 61 grains/neuron) by 10 to 12-fold. A 14-day treatment with the D2 dopamine receptor agonist bromocriptine (BRO) increased pre-proSS mRNA levels by 15 and 28% in intact female and OVX animals, respectively, while the dopaminergic antagonist haloperidol (HAL) decreased the value of this parameter by 20 and 30%. Furthermore, BRO increased pre-proSS mRNA levels by 10 and 20% in intact and castrated male rats, respectively, whereas HAL decreased pre-proSS mRNA levels by 25 and 14% in the same groups of animals. Administration of E2 in combination with HAL in OVX animals increased pre-proSS mRNA levels by 70% compared to those measured in OVX animals treated with HAL alone. In HAL-treated castrated male rats, administration of DHT increased the relative pre-proSS mRNA levels by 35% compared to those measured in castrated animals treated with HAL alone. The present data clearly demonstrate that androgens and estrogens as well as dopamine-mediated mechanisms could play a regulatory role in pre-proSS mRNA levels in somatostatinergic neurons in the hypothalamic PeN in both male and female rats.     

Estrogen modulates parathyroid hormone-induced interleukin-6 production in vivo and in vitro

Interleukin (IL)-6 promotes osteoclastogenesis and is thought to play a role in the bone loss that follows estrogen withdrawal. In vitro studies have demonstrated that IL-6 is produced in response to PTH by cells in the osteoblast lineage and that PTH-induced bone resorption is inhibited by a neutralizing antibody to the IL-6 receptor. In addition, we have recently reported that IL-6 plays a role in PTH-induced bone resorption in humans with chronic PTH excess and in experimental animals during the short-term infusion of PTH. In the current study, we examined whether estrogen withdrawal augments PTH-induced IL-6 production. When cultured in the absence of estrogen, human osteosarcoma cells (Saos-2) treated with PTH demonstrated significantly greater release of IL-6 than cells grown under estrogen-replete conditions, 30-fold vs. 15-fold (P = 0.005). A similar effect but of lesser magnitude was seen with primary human osteoblasts. In vivo, PTH induced IL-6 production was also increased in the estrogen-deficient state (ovx) such that at the end of a 5-day PTH infusion, the mean circulating level of IL-6 was significantly higher in ovx vs. sham/ovx mice (60.1 vs. 16.9 pg/ml; P < 0.0001). The greater increase in circulating levels of IL-6 in PTH-treated ovx mice was paralleled by a greater rise in bone resorption markers with the mean level of urine collagen cross-links in the PTH-treated ovx group being more than 2.5-fold higher than in the PTH-treated sham/ovx animals (236 vs. 88.5 microg/mmol creatinine, P < 0.0001). Mean serum collagen cross-link values were 17.4 microg/liter in PTH-treated ovx vs. 7.4 microg/liter in PTH-treated sham/ovx animals (P < 0.0001). Treatment of animals with estrogen prevented the exaggerated response to PTH infusion such that the increase in both circulating levels of IL-6 and bone turnover markers in estrogen-treated animals were similar to those observed in sham/ovx animals and significantly lower than those in PTH-treated ovx animals. These findings may help to explain the increased skeletal sensitivity to the resorbing effects of PTH seen in the estrogen-deficient state.     

OPG and PTH-(1-34) have additive effects on bone density and mechanical strength in osteopenic ovariectomized rats

PTH is a potent bone anabolic factor, and its combination with antiresorptive agents has been proposed as a therapy for osteoporosis. We tested the effects of PTH, alone and in combination with the novel antiresorptive agent OPG, in a rat model of severe osteopenia. Sprague Dawley rats were sham-operated or ovariectomized at 3 months of age. Rats were untreated for 15 months, at which time ovariectomy had caused significant decreases in bone mineral density in the lumbar vertebrae and femur. Rats were then treated for 5.5 months with vehicle (PBS), human PTH-(1-34) (80 microg/kg), rat OPG (10 mg/kg), or OPG plus PTH (all three times per wk, sc). Treatment of ovariectomized rats with OPG or PTH alone increased bone mineral density in the lumbar vertebrae and femur, whereas PTH plus OPG caused significantly greater and more rapid increases than either therapy alone (P < 0.05). OPG significantly reduced osteoclast surface in the lumbar vertebrae and femur (P < 0.05 vs. sham or ovariectomized), but had no effect on osteoblast surface at either site. Ovariectomy significantly decreased the mechanical strength of the lumbar vertebrae and femur. In the lumbar vertebrae, OPG plus PTH was significantly more effective than PTH alone at reversing ovariectomy-induced deficits in stiffness and elastic modulus. These data suggest that OPG plus PTH represent a potentially useful therapeutic option for patients with severe osteoporosis.