Stanniocalcin kinetics in freshwater and seawater european eel (Anguilla anguilla)

The kinetics and hypocalcemic potency of stanniocalcin (STC) were examined in freshwater and seawater eels. The secretion rate and the metabolic clearance rate of STC were calculated from the STC disappearance curve after intra-arterial injection of trout STC. Basal plasma STC concentrations in freshwater and seawater eels did not differ but the STC secretion rate and metabolic clearance rate in seawater eel were 70–75% higher than in FW eel. The increased STC distribution space in seawater eels suggests that the STC receptor density was increased. STC had a higher hypocalcemic potency in seawater than in freshwater eels. These observations support the hypothesis that seawater fish require more hormonal control over transcellular influx of calcium than freshwater fish.To whom correspondence should be addressed.     

Hormonal regulation of renal inorganic phosphate transport in the winter flounder, Pleuronectes americanus

Intestinal uptake and renal excretion are the primary determinants of inorganic phosphate (P_i) balance in teleosts. In general, teleost kidneys may either reabsorb filtered P_i or secrete excess P_i into the urine. Primary monolayer cultures of flounder (Pleuronectes americanus) renal proximal tubule epithelium (PTCs) have helped identify several hormones that may participate in conservation or excretion of P_i. Mounted in Ussing chambers, the monolayer cultures can be used to assay transepithelial P_i transport. Several factors, including metabolic acidosis, elevation of plasma [P_i], salmon stanniocalcin, salmon somatolactin and mammalian prolactin, have now been shown to alter transepithelial P_i transport in winter flounder PTCs. Salmon stanniocalcin (STC) stimulated P_i luminal-to-peritubular transport (reabsorption) at a dosage of 12.5–50 ng/ml (0.25–1.0 nM). Net P_i transport changed within 30 min and progressively increased from slight net secretion in untreated controls to net reabsorption after 3 h. The target and function of somatolactin have been uncertain. In our hands salmon somatolactin (sSL) also stimulated P_i reabsorption by flounder PTCs in a dose-dependent manner at physiological levels of the hormone (12.5 ng/ml). Net P_i transport was significantly altered by sSL within 2 h after the initial exposure. Neither sSL nor STC had any effect on transepithelial Ca²⁺ transport. The effects of both sSL and STC were mimicked by forskolin, whereas H-89, a highly specific protein kinase A inhibitor, significantly decreased the effects of the hormones as well as forskolin-induced P_i reabsorption. Furthermore, the production and release of cAMP were increased more than two-fold following exposure to STC or sSL. The data indicate that STC and sSL directly stimulate net renal P_i reabsorption by a cAMP-dependent pathway. In addition, mammalian prolactin greatly, and salmon growth hormone slightly, increased net P_i reabsorptive flux, whereas salmon prolactin had no effect. These results appear to be related to the location of the cysteine disulfide bonds within the molecular structure. Although somatolactin and stanniocalcin may both stimulate renal P_i conservation, their actions may be related to different physiological conditions.     

STC-1基因在大、小体型猪中表达与分布的差异分析

试验分别采集40日龄小体型猪（巴马猪）和大体型猪（大白猪）的心脏、肝脏、脾脏、肺脏、肾脏、头骨、骨骼肌组织,利用实时荧光定量PCR检测斯钙素-1（stanniocalcin 1,STC-1）基因mRNA在各个组织中的表达水平,并通过Western blotting检测STC-1蛋白在各个组织中的分布。实时荧光定量PCR检测结果表明,STC-1基因mRNA在巴马猪和大白猪肺脏、肾脏中相对表达水平较高,在骨骼肌中的表达水平最低;除心脏和骨骼肌外,巴马猪其余各组织中STC-1基因mRNA表达水平均显著高于大白猪（P < 0.05）。Western blotting检测结果表明,巴马猪肝脏中STC-1蛋白的表达量最高,而大白猪脾脏中STC-1蛋白表达量最高,两者差异显著（P < 0.05）;巴马猪肺脏、肝脏、骨骼肌及心脏组织中STC-1蛋白表达量均极显著高于大白猪（P < 0.01）;而巴马猪肾脏、脾脏中STC-1蛋白表达量极显著低于大白猪（P < 0.01）。本研究首次对大、小体型猪不同组织的STC-1基因mRNA表达水平及其STC-1蛋白分布进行检测,导致该基因表达与分布差异的原因可能与两种猪受外界环境应激及生长发育差异有关。     

斯钙素2基因在家畜上的研究进展

斯钙素2是斯钙素家族成员之一,最早在鱼上发现,参与鱼体内钙磷平衡的调节,广泛表达于机体的多种组织器官,是一种参与多种生物过程的糖蛋白激素和调节恶性肿瘤进展的分泌蛋白。STC2是一种新的潜在的肿瘤标记的生物分子,且在家畜妊娠、骨骼与体型大小方面等方面也起重要作用。本文主要综述了STC2基因和蛋白的发现、分子结构、及其在动物生理、病理、妊娠、生长等方面的作用,并展望了在我国黄牛育种方面应用的可能性。     

Expression and Distribution Difference Analysis of STC-1 Gene in Big and Small Body Shape Pigs

The heart,liver,spleen,lung,kidney,skull,skeletal muscle were collected from 40-day-old Bama Mini pig and Large White pig,stanniocalcin 1(STC-1) gene mRNA and STC-1 protein were detected with Real-time PCR and Western blotting methods, respectively. The Real-time PCR results showed that the expression level of STC-1 gene mRNA was higher in lung and kidney, but was the lowest in skeletal muscle of Bama Mini pig and Large White pig. Except for heart and skeletal muscle tissues, the expression level of STC-1 gene mRNA in other tissues of Bama Mini pig was significantly higher than Large White pig (P < 0.05).The Western blotting results showed that the STC-1 protein distribution were the highest in liver and spleen of Bama Mini pig and Large White pig, respectively, and the difference was significant (P < 0.05). The STC-1 protein expression in lung, liver, skeletal muscle and heart of Bama Mini pig were extremely significantly higher than Large White pig (P < 0.01),and the STC-1 protein expression in kidney and spleen of Bama Mini pig were extremely significantly lower than Large White pig (P < 0.01). STC-1 gene mRNA and protein were firstly detected in different tissues from big and small body shape pigs,this might have a relationship with various external environments stress and development.     

Catfish electroreceptor organ functioning during five days exposure to different calcium environments

Catfish, Ictalurus melas, were pre-adapted to artificial tap water with 1.2 mM Ca²⁺ for two weeks, and subsequently transferred to artificial tap water with 0.6, 1.2, or 2.2 mM Ca²⁺ for one week in order to investigate the effect of the environmental Ca²⁺-concentration on stimulus encoding and the frequency characteristics in ampullary electroreceptor organs. Within 30 minutes after transfer, the spontaneous activity of the primary afferents, as well as gain and phase of the stimulus induced responses changed transiently corresponding to the Ca²⁺-concentration. One day after transfer the Ca²⁺-induced changes of the spontaneous activity had disappeared as well as the differences between the sensitivities at frequencies of 2, 8, 12, 16 and 20 Hz in 0.6 and 1.2 mM Ca²⁺, whereas at 16 and 20 Hz in 2.2 mM Ca²⁺ the sensitivity was still elevated. The Ca²⁺-induced phase shift was strongly frequency dependent. At 2 Hz no Ca²⁺ effect on the phase was observed, whereas at 12, 16 and 20 Hz significant effects could be demonstrated up till three days after transfer. The latency was not affected by the transfer.The Ca²⁺-induced effects on the primary afferent spontaneous activity are probably related to a Na⁺/Ca²⁺-exchanger at the basal faces of the receptor cells. The frequency dependent effects on gain and phase are concluded to relate to properties of the apical membrane, most likely to Ca-dependent K-channels. These findings further support the concept that ampullary electroreceptor might serve as chemoreceptor organs.