七氟醚后处理对大鼠心肌缺血再灌注时Na+-K+-ATP酶和Ca2+-Mg2+-ATP酶活性的影响

目的 评价七氟醚后处理对大鼠心肌缺血再灌注时Na+-K+-ATP酶和Ca2+-Mg2+-ATP酶活性的影响,探讨其减轻心肌缺血再灌注损伤的机制.方法 健康雄性Wistar大鼠45只,体重250～280 g,随机分为3组(n=15):假手术组(S组)、缺血再灌注组(I/R组)和七氟醚后处理组(Spo组).I/R组和Spo组采用结扎左冠状动脉前降支30 min时进行再灌注的方法制备心肌缺血再灌注模型,S组仅在左冠状动脉前降支下穿线.Spo组再灌注前1 min开始吸入2.5%七氟醚持续5 min.于再灌注2 h时取心肌组织,测定心肌梗死体积、Na+-K+-ATP酶活性和Ca2+-Mg2+-ATP酶活性.结果 与S组比较,I/R组心肌梗死体积扩大,心肌组织Na+-K+-ATP酶和Ca2+-Mg2+-ATP酶的活性降低(P＜0.05);与I/R组比较,Spo组心肌梗死体积缩小,心肌组织Na+-K+-ATP酶和Ca2+-Mg2+-ATP酶的活性升高(P＜0.05).结论七氟醚后处理可提高Na+-K+-ATP酶和Ca2+-Mg2+-ATP酶的活性,从而减轻大鼠心肌缺血再灌注损伤.     

安氟醚麻醉大鼠不同时期脑Ca2+-ATP酶活性变化

目的动态观察安氟醚吸入麻醉大鼠不同时期各脑区Ca2+-ATP酶活性变化和行为学变化,探讨安氟醚的麻醉作用机制.方法 40只SD雌性大鼠随机均分为五组诱导期组、麻醉期组、恢复期组、清醒期组和对照组.分光光度法测定不同时期大脑皮层、脑干、海马Ca2+-ATP酶活性.结果在诱导期各脑区Ca2+-ATP酶活性即开始下降(P＜0.05);麻醉期降至最低(P＜0.01);恢复期又开始升高,但仍低于对照组水平.其中,仅脑干Ca2+-ATP酶活性降低有显著性差异(P＜0.05);清醒期基本恢复至对照组水平(P＞0.05).且行为学变化与脑Ca2+-ATP酶活性变化有关.结论安氟醚的麻醉效应可能与其抑制脑Ca2+-ATP酶活性相关,麻醉深浅与抑制的程度一致.     

Ca2+-Mg2+-dependent ATP-ase activity in hemodialyzed children. Effect of a hemodialysis session

In the course of chronic kidney disease (CKD) the intracellular erythrocyte calcium (Ca_i²⁺) level increases along with the progression of the disease. The decreased activity of Ca²⁺-Mg²⁺-dependent ATP-ase (PMCA) and its endogenous modulators calmodulin (CALM), calpain (CANP), and calpastatin (CAST) are all responsible for disturbed calcium metabolism. The aim of the study was to analyze the activity of PMCA, CALM, and the CANP-CAST system in the red blood cells (RBCs) of hemodialyzed (HD) children and to estimate the impact of a single HD session on the aforementioned disturbances. Eighteen patients on maintenance HD and 30 healthy subjects were included in the study. CALM, Ca_i²⁺ levels and basal PMCA (bPMCA), PMCA, CANP, and CAST activities were determined in RBCs before HD, after HD, and before the next HD session. Prior to the HD session, the level of Ca_i²⁺ and the CAST activity were significantly higher, whereas bPMCA, PMCA, and CANP activities and the CALM level were significantly lower than in controls. After the HD session, the Ca_i²⁺ concentration and the CAST activity significantly decreased compared with the basal values, whereas the other parameters significantly increased, although they did not reach the levels of healthy children. The values observed prior to both HD sessions were similar. Ca_i²⁺ homeostasis is severely disturbed in HD children, which may be caused by the reduction in the PMCA activity, CALM deficiency, and CANP-CAST system disturbances. A single HD session improved these disturbances but the effect is transient.     

氯胺酮对大鼠大脑皮质和丘脑突触体ATP酶活性的影响

目的 动态观察氯胺酮对大鼠大脑皮质和丘脑Na+-K+ATP酶和Ca2+-ATP酶活性的影响。方法 SD大鼠32只,随机分为四组:对照组、麻醉组、恢复I组和恢复Ⅱ组。对照组给予腹腔注射生理盐水10 ml·kg-1,10 min后断头;其它三组均为腹腔注射氯胺酮100 mg·kg-1。其中麻醉组在大鼠翻正反射消失后断头;恢复I组在大鼠翻正反射恢复后断头;恢复Ⅱ组在大鼠完全清醒后断头。在生理盐水冰面上分离双侧大脑皮质和丘脑,以分光光度法测大脑皮质和丘脑Na+-K+-ATP酶和Ca2+-ATP酶活性。结果大鼠腹腔注射氯胺酮后,其大脑皮质的Na+-K+-ATP酶和Ca2+-ATP酶活性分别较对照组降低32.8％和26.2％(P<0.05);丘脑的Na+-K+-ATP酶和Ca2+-ATP酶活性也分别较对照组降低31.4％和24.5％(P<0.05);大鼠翻正反射恢复后和动物完全清醒后两种ATP酶活性的变化与对照组相比差异均无统计学意义(P>0.05)。结论 Na+-K+-ATP酶和Ca2+-ATP酶活性的改变在氯胺酮全麻作用机制中可能起重要作用。     

地氟醚对大鼠心肌细胞质膜钙ATP酶活性的影响

目的 观察地氟醚对心肌细胞质膜Ｃａ＾２＋－ＡＴＰａｓｅ活性的影响，探讨其心肌抑制作用的机制。方法 参照文献方法制备大鼠心肌细胞质膜，观察不同浓度（０％～１１％）地氟醚在底物缓冲液不同钙离子浓度（０．４～２０μｍｏｌ／Ｌ）或反应温度（２５℃、３７℃）时，对质膜Ｃａ＾２＋－ＡＴＰａｓｅ活性的影响。结果 随地氟醚浓度的升高，质膜Ｃａ＾２＋－ＡＴＰａｓｅ活性逐渐下降。同一浓度地氟醚对Ｃａ＾２＋－ＡＴＰａｓ     

Abundance and activity of Ca2+-ATPase in hypercalciuric children

The plasma membrane Ca²⁺-ATPase (PMCA) is one of the main regulators of cell Ca²⁺ homeostasis. The aim of our study was to determine whether the abundance and activity of PMCA are altered in erythrocytes of children with idiopathic hypercalciuria. Twenty-four children with idiopathic hypercalciuria (13 girls and 11 boys, mean age 10.6±4.8 years; mean urinary calcium concentration 0.85±0.20 mmol/mmol creatinine) and 30 healthy age-matched children were enrolled. PMCA protein abundance was determined by Western blot analysis. Enzyme activity was determined spectrophotometrically. The abundance of PMCA did not differ in hypercalciuric patients from that of control subjects (98±22% vs 100±18%). Moreover, the activity was not different between the studied groups (3141±1494 vs 2953±780 nmol ATP/mg protein/h). The extent of hypercalciuria did not correlate with enzyme abundance or activity. Assuming that erythrocytes may reflect the renal tubular transporting processes, our data suggest that other Ca²⁺-transport mechanisms than PMCA might be involved in the development of idiopathic hypercalciuria in children. Received: 5 December 2000 / Revised: 2 May 2001 / Accepted: 3 May 2001     

Decreased erythrocyte (Ca2+ + Mg2+)-ATPase activity in hemodialyzed uremic patients.

Erythrocyte (Ca2+ + Mg2+)-ATPase activity and calcium content were determined in 15 uremic-hemodialyzed patients and 15 normal controls. A decrease in the activity of the enzyme (mean +/- SD = 65 +/- 7 vs. 79 +/- 12 mumol Pi/g Hb/h, p less than 0.001) and a parallel increase in the calcium content (17.2 +/- 6.4 vs. 5.1 +/- 4.2 mumol/L RBC, p less than 0.05) were found in the patients' erythrocytes when compared with those of the controls. It is proposed that malfunction of the calcium pump in hemodialyzed uremic patients is pathophysiologically significant in the accumulation of intracellular calcium. The increased intracellular calcium found in other tissues in uremia may be the result of the systemic malfunction of (Ca2+ + Mg2+)-ATPase in this disorder.     

遗传高钙尿结石大鼠肾小管上皮细胞基底膜钙转运蛋白的异常表达及意义

目的 观察肾小管上皮细胞基底膜钙转运蛋白细胞膜钙泵1b(PMCA1b)和钠钙交换体.(NCX1)在遗传性高钙尿结石(GHS)大鼠肾组织的表达及其在特发性高钙尿症(IH)发病中的作用.方法 雄性遗传高钙尿结石大鼠和正常野生型SD大鼠各6只,采用实时荧光定量PCR检测PMCA1b和NCX1 mRNA表达,westem blot方法 检测其蛋白表达.结果 GHS大鼠与正常对照(NC)组大鼠的NCX1在mRNA水平和蛋白水平比较差异均无统计学意义(P＞0.05);GHS大鼠与NC大鼠的PMCA1b在mRNA水平比较差异无统计学意义(P＞0.05),GHS大鼠的PMCA1b蛋白平均相对吸光度值(A)为(0.18±0.05),NC组为(0.43±0.07),差异有统计学意义(P＜0.01).结论 PMCA1b蛋白表达下降可能是特发性高钙尿症形成的发病机制之一.     

Characterization of a (Ca2+ + Mg2+)-ATPase system in the osteoblast plasma membrane

A high affinity, calmodulin-sensitive (Ca2 + Mg2+)-ATPase was demonstrated in the plasma membrane preparation of three different osteosarcoma cell lines previously demonstrated to respond to parathyroid hormone with an increase in cytosolic calcium and a decrease in pH. The maximal velocity of the enzyme activity in the membrane preparations ranged from 0.83 to 2.42 nmol Pi released per min per mg protein with half-saturation constants of 26 nM of free Ca. The enzyme activity was not affected by Na+, K+, ouabain and azide, and exhibited an absolute requirement for Mg2+ ions. These results suggest a possible role for a membrane Ca2 + Mg2+-ATPase in initiating and perpetuating the ionic control of osteoblastic function.     

Ultracytochemical study of Ca2+-ATPase activity in isolated, superoxide-treated rat brains

The relationship between changes in Ca2+-adenosine triphosphatase (ATPase) activity and plasma membrane damage was histochemically studied by enzymatic electron microscopy in rat brains with and without superoxide treatment. The brains were obtained from male Wistar rats after decapitation, and the control brains were examined immediately. Brains not treated with superoxide were incubated at 20 degrees C for 3, 6, or 12 hours. The superoxide-treated brains were immersed in a hypoxanthine-xanthine oxidase system for 20, 60, or 120 minutes. Ca2+-ATPase activity in the cerebral cortex and hippocampal CA1 was studied by the lead citrate method. Control brains showed Ca2+-ATPase activity in the membrane of the nerve cell body and dendrites, the basement membrane of endothelial cells, and the erythrocyte membrane. In untreated brains, enzymatic activity gradually decreased but was still detected after 12 hours. In those treated with superoxide, enzymatic activity gradually decreased but was still observed after 120 minutes in fragments of the plasma membrane. These findings show that the plasma membrane is more affected by treatment with superoxide than by decapitation itself, and that plasma membrane damage precedes the disappearance of Ca2+-ATPase activity. Residual Ca2+-ATPase activity does not necessarily imply reversibility of cerebral ischemia.     

Properties of Ca2+-Mg2+ ATP-ase in rabbit bladder muscle and mucosa: Effect of urinary outlet obstruction

The contractile response of the smooth muscle of the urinary bladder is dependent upon both the entrance of extracellular calcium through receptor-operated calcium channels and the stimulated release of calcium from the sarcoplasmic reticulum. In addition, partial outlet obstruction induces marked alterations in the utilization of intracellular calcium. Although calcium ATP-ase provides the energy for the translocation of intracellular free calcium into storage sites within the sarcoplasmic reticulum, very little is known about the properties of this enzyme in bladder muscle and mucosa. As an initial study, divalent ion specific ATP-ase activity was measured in extracts of rabbit bladder muscle and mucosa from control animals and from rabbits following partial urinary outlet obstruction. In both normal bladder muscle and mucosa, magnesium and calcium ions were equally effective in activating the enzyme. Seven days following partial urinary outlet obstruction, the ATP-ase activity in both bladder muscle and mucosa was significantly depressed by over 70%. The degree of the decreased enzyme activities observed within the muscularis and mucosa would indicate that specific membrane functions supported by divalent-ion-ATP-ase are dysfunctional. This hypothesis is supported by marked alterations in the utilization of intracellular calcium following partial outlet obstruction and the marked dysfunctions in both mucosal permeability and bacterial adherence to mucosa observed following partial outlet obstruction. © 1996 Wiley-Liss, Inc.     

中医不同治法对骨质疏松症大鼠骨密度及骨骼肌Ca2+-Mg2+-ATP酶影响的比较研究

目的观察中医不同治法对糖皮质激素诱导骨质疏松症大鼠骨密度、骨骼肌Ca2+-Mg2+-ATP酶变化的影响,探讨中医防治骨质疏松症的作用机制。方法将120只雌雄各半的大鼠随机分为正常对照组、模型对照组(模空组)、补肾中药组、健脾中药组、活血化瘀中药组和骨疏康中药组6个组。用地塞米松肌注造模。实验结束后,腹主动脉取血处死大鼠,用酶联免疫法测定大鼠骨骼肌Ca2+-Mg2+-ATP酶,用双能X线骨密度仪测大鼠离体股骨上1/3骨密度。结果①与正常组比较,模空组大鼠离体股骨上1/3骨密度显著降低(P<0.01);与模空组比较,各治疗组大鼠股骨上1/3骨密度均有不同程度的升高,其中以补肾中药组升高程度最为显著(P<0.01),其余各治疗组骨密度较模空组升高程度比较无统计学意义。②与正常组比较,其他各组大鼠骨骼肌的Ca2+-Mg2+-ATP酶显著降低(P<0.01);与模空组比较,各治疗组大鼠骨骼肌的Ca2+-Mg2+-ATP酶均明显升高(P<0.01);补肾组大鼠骨骼肌的Ca2+-Mg2+-ATP酶升高最为明显,明显高于骨疏康组、活血组、健脾组,差异具有非常显著性(P<0.01);活血组大鼠骨骼肌的Ca2+-Mg2+-ATP酶升高程度最低,与补肾组、健脾组、骨疏康组比较具有统计学差异(P<0.01);健脾组和骨疏康组升高程度也比较明显,但二者比较无统计学意义。结论补肾、健脾方法对骨质疏松症大鼠的骨密度和Ca2+-Mg2+-ATP酶具有一定调节作用。     

Separation of odontoblast Ca2+-ATPase and alkaline phosphatase.

Ca2+-ATPase activity was solubilized, partly purified, and separated from nonspecific alkaline phosphatase activity (APase1) of dentinogenically active rat incisor odontoblasts. Attempts were made to extract the enzymes by various agents, such as Triton X-100, deoxycholate, butanol, EDTA, and buffers of decreasing ionic strength. Solubilization by butanol followed by extraction with low concentrations of EDTA proved to be most effective. Purification and separation were done by molecular sieve chromatography. Ca2+-ATPase showed no activity against p-nitrophenyl phosphate (p-NPP) or inorganic pyrophosphate (PPi) and was unaffected by R 8231 [+/-)-6(m-bromophenyl)-5,6-dihydroimidazo(2,1-b)thiazole oxalate]. It was activated by Ca2+ and Mg2+ ions in equimolar concentrations with the substrate. The enzyme was rapidly inactivated in the solubilized state. An apparent molecular weight of about 18,000 was obtained from molecular sieve data. APase, showing activity against ATP, PPi, and p-NPP, was virtually totally inhibited by R 8231. It was activated by Mg2+ ions but slightly reduced in activity by Ca2+ ions. It had an apparent mol. wt. of 79,000. The results provide direct evidence for earlier suggestions of the existence in hard tissue forming cells of two phosphatases active at alkaline pH.     

Ca2+-ATPase in hard tissue forming cells

Conclusions We have shown that in active odontoblasts of the rat incisor tooth, used as a model system for hard tissue forming cells, two enzymes capable of degrading ATP exist. One can be inhibited by levamisole and R 8231 and is probably identical with non-specific alkaline phosphatase (APase). The activity of the other enzyme, tentatively named “Ca-ATPase”, is dependent on the presence of Ca²⁺ or Mg²⁺ and is activated by these ions. The “Ca-ATPase” is unaffected by ouabain and ruthenium red. It may be speculated that the “Ca-ATPase” is concerned with the transmembraneous transport of Ca²⁺ ions to be mineralization front.     

Characterization of a Ca2(+)-ATPase in osteoclast plasma membrane

The plasma membrane fraction of chicken osteoclasts was purified utilizing 20% continuous Percoll gradients. Biochemical marker enzyme analysis (ouabain-sensitive Na+,K(+)-ATPase and 5'-nucleotidase) indicated that plasma membrane enrichment was 11.87-fold and 7.25-fold, respectively, and contamination with mitochondria, endoplasmic reticulum, and lysosomes was low as determined by succinic dehydrogenase, NADH dehydrogenase, and N-acetylglucosaminidase activities, respectively. SDS latency of Na+,K(+)-ATPase and 5'-nucleotidase activities of the isolated plasma membranes revealed that 43-50% of vesicles were sealed, with 10-16% in the inside-out orientation, depending on the membrane fraction used. Electron microscopy confirmed the vesicular nature of the plasma membrane fraction. The plasma membrane Ca2(+)-ATPase had a high-affinity (KCa = 0.22 microM; Vmax = 0.16 mumol/mg per min) and a low-affinity (KCa = 148 microM; Vmax = 0.37 mumol/mg per min) component. Calmodulin (0.12 microM) had no effect on Ca2(+)-ATPase activity. However, trifluoperazine (0.1 mM), a calmodulin antagonist, strongly inhibited especially the high-affinity component of the enzyme. Vanadate and lanthanum also caused inhibition. In the presence of CDTA, a potent Ca2+ and Mg2+ chelating agent, high-affinity Ca2(+)-ATPase activity was abolished, indicating that trace Mg2+ was essential for activity. The Ca2(+)-ATPase substrate curve using ATP showed a high-affinity (Km = 12.3 microM; Vmax = 0.022 mumol/mg per min) and a low-affinity (Km = 43.8 microM; Vmax = 0.278 mumol/mg per min) component. These results demonstrate that osteoclasts have a plasma membrane Ca2(+)-ATPase with characteristics similar to the enzyme responsible for active calcium extrusion in other cells.     

Epithelial Ca2+ and Mg2+ channels in kidney disease

Many physiological functions rely on the precise maintenance of body calcium (Ca2+) and magnesium (Mg2+) balance, which is tightly regulated by the concerted actions of intestinal absorption, renal reabsorption, and exchange with bone. The kidney plays an important role in the homeostasis of divalent ions. Most Ca2+ and Mg2+ reabsorption occurs in the proximal tubules and the thick ascending limb of Henle's loop via a passive paracellular pathway. At the level of the distal convoluted tubule (DCT) and the connecting tubule (CNT), Ca2+ and Mg2+ are reabsorbed via an active transcellular route. Reabsorption of divalents in these latter segments is regulated in a Ca2+ and Mg2+-specific manner and determines the final excretion in the urine. Importantly, genetic studies, as well as molecular cloning strategies, recently identified epithelial ion channels as the gatekeepers of active Ca2+ and Mg2+ reabsorption. These channels are members of the transient receptor potential (TRP) superfamily. TRP vanilloid 5 (TRPV5) is responsible for the rate-limiting Ca2+ entry, and TRP melastatin 6 (TRPM6) constitutes the apical entry step in Mg2+ reabsorption. Dysregulation or malfunction of these influx pathways has been associated with renal Ca2+ and Mg2+ wasting. This review updates the current knowledge and the recent advances of Ca2+ and Mg2+ reabsorption and related disorders.     

Separation of odontoblast Ca2+-ATPase and alkaline phosphatase

Summary Ca²⁺-ATPase activity was solubilized, partly purified, and separated from nonspecific alkaline phosphatase activity (APase) of dentinogenically active rat incisor odontoblasts. Attempts were made to extract the enzymes by various agents, such as Triton X-100, deoxycholate, butanol, EDTA, and buffers of decreasing ionic strength. Solubilization by butanol followed by extraction with low concentrations of EDTA proved to be most effective. Purification and separation were done by molecular sieve chromatography. Ca²⁺-ATPase showed no activity againstp-nitrophenyl phosphate (p-NPP) or inorganic pyrophosphate (PP_i) and was unaffected by R 8231 [(±)-6(m-bromophenyl)-5,6-dihydroimidazo(2,1-b)thiazole oxalate]. It was activated by Ca²⁺ and Mg²⁺ ions in equimolar concentrations with the substrate. The enzyme was rapidly inactivated in the solubilized state. An apparent molecular weight of about 18,000 was obtained from molecular sieve data. APase, showing activity against ATP, PP_i, andp-NPP, was virtually totally inhibited by R 8231. It was activated by Mg²⁺ ions but slightly reduced in activity by Ca²⁺ ions. It had an apparent mol. wt. of 79,000. The results provide direct evidence for earlier suggestions of the existence in hard tissue forming cells of two phosphatases active at alkaline pH.     

Effect of diabetes on cytosolic free Ca2+ and Na(+)-K(+)-ATPase in rat aorta.

We examined Na(+)-K(+)-ATPase activity and the levels of alpha I-, alpha II-, and beta-subunit mRNA and protein in aortic cells of diabetic rats. Diabetes was induced by streptozocin. Na(+)-K(+)-ATPase activity was significantly reduced on the 2nd day of diabetes (9.4 +/- 1.3 vs. 17.5 +/- 2.1 mumol NADH.mg-1 protein.h-1, P less than 0.05) and remained depressed on days 7 and 14. The levels of 5.3-kilobase (kb) mRNA band of the catalytic alpha II-subunit of Na(+)-K(+)-ATPase were also decreased on the 2nd day of diabetes, whereas the second band, 3.4 kb, was not affected. Both bands were significantly decreased on days 7 and 14. This was followed by a reduction in the levels of alpha II-protein (day 14). The levels of alpha I- and beta-subunit mRNA and alpha I- protein were not affected by diabetes. A decrease in Na(+)-K(+)-ATPase activity was accompanied by a significant (P less than 0.001) increase in the cytosolic free Ca2+ concentrations [( Ca2+]i) in diabetic aortic cells (221 +/- 18 nM on the 7th day and 242 +/- 17 nM on the 14th day vs. 153 +/- 7 nM in controls). These findings are consistent with the hypothesis that decreased Na(+)-K(+)-ATPase activity and gene expression in vascular smooth muscle cells with accompanied rises in [Ca2+]i may be an important pathogenetic factor in the development of hypertension and atherosclerosis in diabetes.     

Activation of a Ca2+-Mg2+-dependent endonuclease as an early event in castration-induced prostatic cell death

Previous studies have demonstrated that castration-induced androgen withdrawal results in the fragmentation of prostatic DNA into nucleosomal oligomers, and this process comprises an early event in the activation of programed cell death in the rat ventral prostate. This DNA fragmentation could be due to changes in the chromatin conformation increasing its sensitivity to preexisting nucleases and/or to increases in the activity of the nucleases themselves. However, comparative kinetic analysis of in vitro DNA fragmentation induced by exogenous nucleases did not reveal any differences in the sensitivity of prostatic chromatin between intact and castrated rats. In contrast to these negative findings, using [3H] DNA as an exogenous substrate, it was shown that within the first day following castration there was a twofold increase in a Ca2+-Mg2+-dependent nuclease activity without a concomitant increase in other nuclear nucleases. This Ca2+-Mg2+-dependent nuclease activation occurred coincidental with the initial increase in nuclear DNA fragmentation following castration and preceded the enhanced appearance of morphological changes characteristic of dying cells (i.e., apoptosis), as well as the major increase in prostatic DNA loss. These results suggest that castration-induced androgen deprivation leads to a sequential activation of a Ca2+-Mg2+-dependent nuclease leading to the fragmentation of the genome into discrete nucleosomal-sized fragments of DNA, subsequently followed by the fragmentation of the nucleus itself (i.e., apoptosis) and eventually with the complete digestion of the nucleosomal oligomers into component nucleotides (i.e., DNA loss). Since the castration-induced nuclease is dependent upon calcium ions for maximal activity, a potential role of intracellular calcium in the early events activating prostatic cell death was investigated. Acute disturbances in intracellular calcium homeostasis within the ventral prostate by means of a potent calcium influx blocker, nifedipine, simultaneous with castration, resulted in a significant delay in the biochemical and morphological changes associated with prostatic cell death (i.e., prostatic weight loss, prostatic DNA loss, and DNA fragmentation). These results point to a potential role of intracellular calcium levels in the mechanism of activation of castration-induced death of the androgen-dependent epithelial cells in the ventral prostate.     

Na+-K+-ATPase pumping activity is not directly linked to myo-inositol levels after sorbinil treatment in lenses of diabetic rats

Changes in tissue levels of sorbitol, myo-inositol, and Na+-K+-ATPase enzyme activity have been implicated in the development of diabetic complications in animal models of the disease and in humans. The ability of the aldose reductase inhibitor sorbinil to reverse the hyperglycemia-induced changes in these lenticular metabolite and enzyme-activity levels in the streptozocin-induced diabetic rat was examined to determine what, if any, relationship exists between these changes. Two weeks of untreated diabetes did not change ouabain-inhibitable ATPase enzyme activity assayed in lens homogenates but did result in a decrease in the Na+-K+-ATPase transport activity as measured by 86Rb uptake in the intact lens. This was accompanied by a 100-fold increase in the levels of sorbitol and significant decreases in the levels of myo-inositol, ATP, and glutathione in the lens. Whereas all of these changes could be reversed by sorbinil treatment, the dose required for restoration of the depleted myo-inositol level (ED50 greater than 20 mg.kg-1.day-1) was much higher than the dose required to reverse the other changes (ED50 range 2-5 mg.kg-1.day-1). These results suggest that the restoration of lenticular Na+ -K+ -ATPase activity is not secondary to a normalization of myo-inositol levels and may provide evidence that the two parameters are not strictly associated in diabetic tissues.