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Results for “Calcium-Transporting ATPases”

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At least 1,369 records · Page 76Linked to original sources
PubMed1990

[Rational approaches to selective synthesis of antimetastatic agents].

Some 3,3-dimethyltriazenes were shown to be capable of selective antimetastatic activity, i. e. preventing metastatic spreading of experimental tumors without affecting primary tumor or apparent metastases. The mechanism of antimetastatic effect of 3,3-dimethyltriazenes is discussed. The drugs represent a new promising pharmacological class of agents used for postsurgical adjuvant treatment of cancer. The effect of diazo derivatives produced in the course of disintegration of aromatic and heterocyclic 3,3-dimethyltriazenes on the in vitro activity of Ca-ATPase of the sarcoplasmic reticulum should be evaluated as a test-system for selecting new antimetastatic agents with cryptodiazonic properties.

Animals↗
PubMedDate not supplied

Deoxycorticosterone prevents the blood pressure-lowering effect of calcium in spontaneously hypertensive rats.

To study the effects of prolonged oral calcium loading on the development of hypertension in spontaneously hypertensive rats (SHR), 48 male animals (age 9 weeks) were divided into four groups according to the treatment: control, calcium, deoxycorticosterone (DOC) and calcium/DOC. Both calcium groups received 1.5% calcium chloride solution ad libitum as their drinking fluid. The animals in the DOC groups were treated with a mineralocorticoid, deoxycorticosterone trimethylacetate 25 mg kg-1 s.c. once a week. Systolic blood pressure (BP) was measured twice a week during the 4-week study period. Calcium loading alone lowered BP (p less than 0.01) after four weeks. Combined with DOC treatment, calcium administration had no significant effect on BP. Calcium loading increased the total plasma calcium concentration in the calcium group (p less than 0.05). Urinary excretions of sodium and potassium were augmented in both groups receiving calcium compared to DOC group. DOC treatment alone increased the excretion of calcium (P less than 0.05). Calcium supplementation decreased the plasma phosphate concentration in both groups (calcium p less than 0.05; calcium/DOC p less than 0.01) as well as the excretion phosphate (p less than 0.005) compared to control. The urinary excretion of cAMP remained unaffected by the calcium treatment. The present results indicate that mineralocorticoid treatment can prevent the BP-lowering effect of calcium in SHR. The mechanism of this action remains unclear, but it does not seem to depend on electrolyte or phosphate balance. The investigation of this action of DOC may provide a means for further exploration of the mechanisms by which increased calcium intake lowers BP in SHR.

Animals↗
PubMed1990

dl-N,N'-dicarboxamidomethyl-N,N'-dicarboxymethyl-1,2-diaminopropane (ICRF-198) and d-1,2-bis(3,5-dioxopiperazine-1-yl)propane (ICRF-187) inhibition of Fe3+ reduction, lipid peroxidation, and CaATPase inactivation in heart microsomes exposed to adriamycin.

Iron-catalyzed free radical reactions, such as the peroxidation of membrane lipids or the inactivation of critical enzymes, have been implicated in the cardiotoxicity of Adriamycin. Fe3+ reduction is an important step in both processes. The reduction of Fe3+, Fe3+ ADP, or Fe3(+)-ferritin by rabbit heart microsomes, Adriamycin, and NADPH was 10% inhibited by ICRF-187 (ADR-529) in N2 and 77% inhibited by ICRF-198, the hydrolysis product of ICRF-159 (the racemic form of ICRF-187). Lipid peroxidation and CaATPase inactivation catalyzed by Fe3+, Fe3+ ADP, or Fe3(+)-ferritin were substantially inhibited by ICRF-198 but only partially inhibited by ICRF-187. The cardioprotective action of ICRF-187 during Adriamycin treatment may be a result of its hydrolysis to the d isomer of ICRF-198 which inhibits reduction of Fe3+, thus limiting the role of iron in tissue damaging free radical reactions.

Animals↗
PubMed1990

[Changes in RBC Ca2(+)-ATPase activity and red-cell calcium concentration during dialysis in patients with uremia].

The changes of RBC Ca2(+)-ATPase activity and red cell calcium concentration during dialysis were observed in 19 patients with uremia. The results showed that in 12 patients treated by haemodialysis the RBC Ca2(+)-ATPase activity was lowered an average of 35 U than that in the controls (P less than 0.001); whereas red cell calcium was increased about 5 times (P less than 0.001). After a four-hour haemodialysis, the Ca2(+)-ATPase activity increased 20 U (P less than 0.05); and red cell calcium decreased 45 mumol/L cells (P less than 0.05). In 7 patients treated by CAPD the RBC Ca2(+)-ATPase activity was reduced to 60% of that in the controls (P less than 0.001); and red cell calcium was about 5 times as high as that in the controls (P less than 0.001). After one month of CAPD, the Ca2(+)-ATPase activity increased only 10 U (P greater than 0.05); but red cell calcium decreased 66 mumol/L cells (P less than 0.01).

Adult↗
PubMed1990

Inhibition of the calcium pump by human parathyroid hormone-(1-34) and human calcitonin in liver plasma membranes.

The effect of human parathyroid hormone-(1-34) (hPTH) and human calcitonin (hCT) on the activity of the Ca2(+)-extrusion pump in liver plasma membranes was studied. Both hormones were found to be potent inhibitors of Ca2+ transport and the related high-affinity (Ca2(+)-Mg2+)-ATPase activity, causing maximal inhibition of 25-30% at concentrations of 100 nM. Half-maximal inhibition was observed with 20 nM-hPTH and with 0.5 nM-hCT. By comparison, salmon calcitonin and intact bovine parathyroid hormone-(1-84) were inhibitory only at 10 microM. The effects of hCT and hPTH on the Ca2+ pump activity were not mimicked by cyclic AMP. Also, 10 microM of either hPTH-(1-34) or hCT did not alter the 45Ca2+ influx rate into isolated hepatocytes. We conclude that inhibition of Ca2+ efflux, rather than the stimulation of Ca2+ influx, may play a functional role in the control of hepatic calcium homeostasis by hPTH-(1-34) and hCT.

Biological Transport, Active↗
PubMed1979

Toxic substances and cell membrane function.

The exposed location and functional importance of cell membranes make them particularly susceptible to the toxic effects of many chemicals. The likelihood of such effects has been appreciated for many years. However, the recent advent of new techniques has greatly increased our understanding of the complexities of membrane structure and function. These data make it quite clear that the interaction of toxic compounds with either the protein or the lipid component of cell membranes may substantially alter membrane function. This paper summarizes the current concepts of membrane structure and function and discusses the techniques currently in use to study cell membranes. Several examples are presented in which xenobiotics significantly alter membrane function. These include effects of heavy metals on passive ion permeability, impairment of osmoregulation and calcium transport by organochlorine pesticides, inhibition of the transport of neurotransmitter metabolites by phenoxyacetic acid herbicides in choroid plexus, and reduction in intestinal nutrient transport by heavy metals. Hence the study of the interactions of foreign compounds with membrane function may enhance our understanding of mechanisms both of toxicity and of basic membrane function.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1979

Nerve cell calcium as a messenger for opiate and endorphin actions.

The studies outlined in this chapter provide convincing evidence for the role of calcium in pharmacological and biochemical actions of opiates on the central nervous system. The ability of the synaptosomes to accumulate excess calcium during narcotic exposure represents a singular major example of cellular adaptation at the level of the membrane. These findings together with the possibility that CDR and calcium may mediate a number of processes involving neurotransmitter activity provide many avenues for the future study of opiates and other central nervous system depressants.

Animals↗
PubMed1979

Na,K-ATPase in excitation-contraction coupling of vascular smooth muscle from cattle.

Lowering the extracellular K+ content from 6 to 0.6 mM causes a rise, and elevation from 6 to 8.5 mM a fall of 45Ca++ efflux from the vascular smooth muscle cells of the arteria carotis communis of cattle. In contrast, a level of 17 mM K+ has no influence. Removal of extracellular calcium does not block these effects. 10(-4) M ouabain also induces a rise in Ca++ efflux, additional potassium reduction then being without effect; 10(-9) M ouabain is of no influence. The 45Ca++ efflux kinetics correlates with the activity of the isolated Na,K-ATPase. Tonus increases of the vascular strips by 10(-4) M ouabain and potassium deficiency cannot be blocked by 4 mM lanthanum or removal of extracellular calcium. Unlike sodium, potassium stimulates the active Ca++ binding and the activity of the Ca-ATPase of the microsomal fraction. The ative Ca++ binding of the mitochondria is stimulated by both ions. It is postulated that the activity of the plasma membrane Na,K-pump is able to regulate the tonus of big arteries through alteration of Ca++ storage processes.

Animals↗
PubMed1979

[Biochemical mechanisms for the effect of alcohol on the brain].

This paper reviews and discusses basic knowledge of biochemical mechanisms of action of ethanol upon the central nervous system, the emphasis being on effects upon cerebral membrane structures and processes as well as mechanisms of chemical synaptic transmission. Results of detailed studies into material and steric changes in membranes, ion-dependent adenosine triphosphatases, variations in ion balance, effects upon cyclic nucleotides, influences on special transmitter systems, and mechanisms of formation of morphine-analogous condensation products are presented. In addition, open questions are derived and formulated in problem complexes.

Acetaldehyde↗
PubMed1979

[Studies of the presence of enzymes in various tissues of swine. 5. Studies of the activity and properties of adenosine triphosphatases in the pancreas].

Studies were conducted into the activities of magnesium-ATPase, sodium-potassium-ATPase, and HCO3-ATPase in homogenates of pancreas of 19 foetuses, with body weights between 340 g and 1,642 g, two piglets, with body weights of 9 kg and 10 kg, and four adult pigs. While general enzyme activity was low during foetal development, highest activies usually were recordable from HCO3-ATPase. High activities were recorded from both the piglets and adult pigs. The highest data, again, were recordable from HCO3-ATPase which is essential to the secretion of HCO3 ions. Maximum activity of magnesium-ATPase was based on an ATP-magnesium ratio of 1:1. HCO3-ATPase was best activated by 25 mM NaHCO3 and exhibited high stability to temperature. The activities of magnesium-ATPase and of HCO3-ATPase were inhibited by 10 mM of Rhodanid. Calcium-ATPase reached its maximum activity in response to 5 mM calcium concentration.

Adenosine Triphosphatases↗
PubMed1979

[Role of calcium in realization of nervous control during RNA synthesis in skeletal muscles].

The effects of Ca2+ on the RNA polymerase activity of the nuclei isolated from normal and denervated gastrocnemius muscles of the rabbit were studied. It was shown that 18 hrs after denervation the RNA synthesis in vitro, Ca2+ content and the Ca, Mg-ATPase activity of the nuclei are decreased. After addition of exogenous Ca2+ the incorporation of labelled UTP into the nuclei is stimulated in the denervated muscle and is inhibited in the control. Electrostimulation of the denervated muscle at the peripheral part of the sciatic nerve for 3 hrs increases both the RNA synthesis in the nuclei and the Ca2+ content, as well as the Ca, Mg-ATPase activity. Exogenous Ca2+ has an inhibitory effect on the nuclei of the stimulated muscle. The correlation established is indicative of participation of Ca2+ in the transmission of excitation in skeletal muscle sarcolemma to the processes occurring in nuclear structures.

Animals↗
PubMedDate not supplied

[The effect of catecholamines on the Ca2(+)-adenosinetriphosphatase of the sarcoplasmic reticulum in the skeletal muscles in chicken ontogeny].

It has been shown that the activity of Ca(2+)-ATPase increases during development. Epinephrine in vivo increases the activity of Ca(2+)-ATPase in chick skeletal muscles. The effect of hormone is lacking at embryonic stages of development and appears only before hatching. In the presence of exogenous protein kinase, cAMP also increases the activity of the enzyme, this effect being observed also in embryonic muscles. Lack of effect of epinephrine on Ca(2+)-ATPase in embryonic muscles is associated with non-reactivity of their adenylate cyclase to catecholamines. Ca(2+)-ATPase itself already at embryonic period is ready to react to cAMP. It is concluded that Ca(2+)-ATPase of sarcoplasmic reticulum is one of the sites of action of catecholamines on calcium metabolism in muscle cell and that this action is realized via the system adenylate cyclase-cAMP-protein kinase.

Animals↗