Intragranular co-storage of neuropeptide Y and arginine vasopressin in the paraventricular magnocellular neurons of the rat hypothalamus

Summary Certain populations of arginine vasopressin (AVP) neurons in the magnocellular paraventricular nucleus became immunoreactive for neuropeptide Y (NPY) when rats were treated with colchicine or monosodium glutamate (MSG). The co-storage of these peptides was examined by empooying a post-embedding electron-microscopic immunohistochemistry technique using goldlabeled antibodies to the two peptides. In colchicinetreated rats, the neuronal perikarya contained numerous secretory granules showing co-storage of the two peptides. The cells of the MSG-treated rats were characterized by having well-developed Golgi bodies with the granular structures also co-storing the two peptides, although the secretory granules in the perikarya were rather fewer than in the colchicine-treated rats. It is concluded that the destruction of the arcuate nucleus by MSG-treatment may potentiate the synthesis of NPY in AVP neurons, the synthesis of which is latent in intact animals.     

垂体在刺激脑内渗透压感受器引起的肾脏反应中的作用

实验在α氯醛糖和氨基甲酸乙酯混合麻醉的大鼠中进行。脑室内注射高张盐水(icv.HS)后,肾血浆流量、肾小球滤过率、尿量、尿钠排出量、尿钾排出量和渗透物质清除率均增加,游离水清除率下降。去除垂体后,icv.HS不再能引起上述肾脏反应。另外给大鼠静脉注射血管升压素(VP)拮抗剂(V_1和V_2受体拮抗剂),并不能削弱上述icv.HS引起的肾脏反应。脑室内注射高张盐水后,尿中多巴胺(DA)排出量无显著增多;给予多巴脱羧酶抑制剂苄丝肼也不能削弱icv.HS引起的肾脏反应。上述实验结果表明,在本实验条件下刺激脑内渗透压感受器引起的肾脏反应依赖于垂体的完整性,但看来并不依赖于外周的VP和DA,故垂体通过何种机制介导icv.HS引起上述肾脏反应,有待于进一步的研究。     

垂体后叶素和加压素对离体心肌的直接作用

本实验采用大鼠离体右心房和右心室肌条模型,观察了垂体后叶素和加压素对右心房和右心室肌的直接作用。结果表明:垂体后叶素对右心房的自主性收缩频率和幅度及右心室肌的收缩幅度均有剂量依赖性抑制作用;加压素对右心房和右心室肌收缩幅度也有剂量依赖性抑制作用,但对右心房自主节律无影响;催产素对右心房的收缩频率和幅度则均无影响。加压素V_1、V_2受体拮抗剂d(CH_2)_5Tyr(Me)AVP和d(CH_2)_5(D-Ile~2,Ile~4,Ala(NH_2)~9)AVP对垂体后叶素的负性变力作用具有不同程度的阻断作用,但对垂体后叶素的负性变时作用无阻断作用。以上结果提示,垂体后叶素的负性变力作用主要是由加压素产生的,加压素对心肌有直接的负性变力作用;垂体后叶素的负性变时作用可能是非加压素和催产素成分的作用结果。     

31P NMR analysis of intracellular pH of Swiss mouse 3T3 cells: Effects of extracellular Na+ and K+ and mitogenic stimulation

Summary Swiss mouse 3T3 cells grown on microcarrier beads were superfused with electrolyte solution during continuous NMR analysis. Conventional³¹P and¹⁹F probes of intracellular pH (pH _c ) were found to be impracticable. Cells were therefore superfused with 1 to 4mm 2-deoxyglucose, producing a large intracellular, pH-sensitive signal of 2-deoxyglucose phosphate (2DGP). The intracellular incorporation of 2DGP inhibited the Embden-Meyerhof pathway. However, intracellular ATP was at least in part retained and the cellular responsivity to changes in extracellular ionic composition and to the application of growth factors proved intact. Transient replacement of external Na⁺ with choline or K⁺ reversibly acidified the intracellular fluids. Quiescent cells and mitogenically stimulated cells displayed the same dependence of shifts in pH _c on external Na⁺ concentration (c _Na ^o ). pH _c also depended on intracellular Na⁺ concentration (c _Na ^o ). Increasingc _Na ^c by withdrawing external K⁺ (thereby inhibiting the Na,K-pump) caused reversible intracellular acidification; subsequently reducingc _Na ^o produced a larger acid shift in pH _c than with external K⁺ present. Comparison of separate preparations indicated that pH _c was higher in stimulated than in quiescent cells. Transient administration of mitogens also reversibly alkalinized quiescent cells studied continuously. This study documents the feasibility of monitoring pH _c of Swiss mouse 3T3 cells using³¹P NMR analysis of 2DGP. The results support the concept of a Na/H antiport operative in these cells, both in quiescence and after mitogenic stimulation. The data document by an independent technique that cytoplasmic alkalinization is an early event in mitogenesis, and that full activity of the Embden-Meyerhof pathway is not required for the expression of this event.     

Arginine vasopressin causes morphological changes suggestive of fluid transport in rat choroid plexus epithelium

Summary The experiments described herein use an in vitro preparation of choroid plexus to demonstrate that it is a vasopressin-responsive organ by morphologic criteria. Choroid plexus from rats was incubated for one hour in graded concentrations of arginine vasopressin (AVP). Within physiologic range of molar concentration, incubation in vasopressin induced a decrease in basal and lateral spaces in choroid plexus epithelial cells as well as an increase in number of dark cells. The number of cells with basal spaces decreased significantly from 82.7±9.2 in control tissue to 19±18 in tissue incubated in 10^-12 M AVP; similarly, the number with lateral cellular spaces decreased from 20±8.8 to 7.6±2.2 cells in 10^-10 M AVP. Dark cells increased in number from 3.8±2.6 in control conditions to 49±4 with 10^-9 M vasopressin. These data suggest important effects of arginine vasopressin in cerebrospinal fluid (CSF) on choroid plexus, compatible with enhanced fluid transport across choroid epithelial cells.     

Altered free calcium transients in pig kidney cells (LLC-PK1) cultured with penicillin/streptomycin

Summary The effect of a conventional antibiotic (penicillin/streptomycin) mixture on the widely used kidney epithelial cell line, LLC-PK₁, was investigated by measuring growth and intracellular free calcium. Free calcium concentration was the same in cells cultured for 3 to 7 wk with (“plus”) and without (“minus”) antibiotics both at rest and when challenged with high (14 mM) external calcium. When exposed to vasopressin, minus cells exhibited significantly smaller calcium transients than plus cells. A similar difference existed for transients elicited by a calcium ionophore, 4-br-A23187. After longer periods of culture (>20 wk), minus cells grew slower than plus cells but on reaching confluence (minus cells took 1 day longer) the morphologies and viabilities were indistinguishable. The finding that culture with penicillin/streptomycin reversibly modified some properties of LLC-PK₁ cells, at least partly through altered calcium homeostasis, is of importance for workers using this cell model to study drug effects and raises the general possibility of similar effects on other cultured cells.     

糖皮质激素及其他甾体激素对大鼠下丘脑薄片释放精氨酸加压素的影响

本工作采用离体孵育技术,观察大鼠下丘脑薄片（含有室旁核和视上核）释放精氨酸加压素（ＡＶＰ）和糖皮质激素（ＧＣ）及其他甾体激素对ＡＶＰ释放的快速影响。结果如下：（１）大鼠下丘脑薄片经过９０ｍｉｎ的恢复之后,在长达６ｈ的孵育过程中能够相当稳定地释放ＡＶＰ,释放量为９．０６±１．２３ｐｇ／ｍｉｎ;（２）皮质酮（Ｂ）在２０ｍｉｎ内可明显地抑制ＡＶＰ的释放,在１０－７—１０－４ｍｏｌ／Ｌ范围内呈剂量－效应关系;（３）在同一剂量（１０－６ｍｏｌ／Ｌ）,皮质醇、１７β－雌二醇和睾丸酮也可快速地抑制ＡＶＰ的释放,而相同剂量的地塞米松、醛固酮、孕酮、ＲＵ４８６和胆固醇却无此效应;（４）ＲＵ４８６（１０－７—１０－３ｍｏｌ／Ｌ）对ＡＶＰ的释放没有影响,但却能（１０－５—１０－３ｍｏｌ／Ｌ）部分地阻断Ｂ的快速抑制效应。这些结果表明,ＧＣ对大鼠下丘脑ＡＶＰ的释放具有不通过传统的基因组机制的快速抑制效应,此种抑制效应可能与ＧＣ的负反馈调节作用有关。     

电刺激兔肾脏传入神经对血压,心率及加压素释放的影响

本工作以兔为实验对象,观察电刺激肾脏传入神经（ＡＲＮ）对血压、心率、颈交感神经放电、以及加压素（ＡＶＰ）合成和释放的影响,并对ＡＲＮ进入中枢的通路作了观察。结果显示,电刺激ＡＲＮ可以引起血压下降、心率减慢、颈交感神经放电抑制等反应,ＡＲＮ的兴奋还可使下丘脑的视上核、室旁核中的ＡＶＰ含量增加,垂体中ＡＶＰ含量下降,血浆ＡＶＰ水平升高。硝普钠的降压实验和静脉注射ＡＶＰ受体阻断剂ＡＶＰａ的实验均证实了Ａ     

Secretion of neurophysins by the ovary in sheep

Measurements of venoarterial concentration differences across the ovary in anesthetized sheep have demonstrated that the ovary secretes ovine neurophysin I/II (oNP I/II) and that this process is stimulated by the prostaglandin F2 alpha analogue, cloprostenol. A parallel increase in the secretion of oxytocin (OT) was observed in response to cloprostenol, and the mean molar ratio of oNP I/II to OT secreted was 1.2. There was no detectable ovarian secretion of oNP III. Secretion of oNP I/II and OT was absent after hysterectomy. The data support other evidence indicating that the corpus luteum synthesizes OT, and confirm that the neurophysin associated with OT in the sheep is oNP I/II.     

Effect of monensin on osmotic water flow across the toad bladder and its stimulation by vasopressin and cyclic AMP

Summary The effects of the sodium ionophore monensin on osmotic water flow across the urinary bladder of the toadBufo marinus were studied. Monensin alone did not alter osmotic water flow; however, the ionophore inhibited the hydrosmotic response to vasopressin and cyclic AMP in a dose-dependent manner. The inhibitory effects of monensin were apparent when the ionophore was added to the serosal bathing solution but not when it was added to the mucosal bathing solution. The inhibitory effect of serosal monensin required the presence of sodium in the serosal bathing solution but not the presence of calcium in the bathing solutions. Thus, it appears that intracellular sodium concentration is a regulator of the magnitude of the hydrosmotic response to vasopressin and cyclic AMP.