Calcium intracellular transport

The duodenum and jejunum are capable of both absorption and secretion but absorption usually predominates. Regulation of intestinal secretion and absorption is highly complex and involves extrinsic and intrinsic neural stimuli, numerous receptor types and intercellular and intracellular transport pathways. Intracellular pathways of electrolyte transport involve membrane-associated receptors that activate cyclic nucleotide metabolism, membrane calcium channels and intracellular calcium metabolism, luminal and basal chloride channels and multiple sodium transport channels. Cholinergic stimuli tend to stimulate intestinal... 

The influx of Ca(Il) across the presynaptic membrane is essential for nerve signal transmission involving excitation by acetylcholine (26). Calcium is important in transducing regulatory signals across many membranes and is an important secondary messenger hormone. The increase in intracellular Ca(Il) levels can result from either active transport of Ca(Il) across the membrane via an import channel or by release of Ca(Il) from reticulum stores within the cell. More than 30 different proteins have been linked to regulation by the calcium complex with calmoduhn (27,28). 

Additional cellular events linked to the activity of blood pressure regulating substances involve membrane sodium transport mechanisms Na+/K.+ ATPase Na+fLi countertransport Na+ -H exchange Na+-Ca2+ exchange Na+-K+ 2C1 transport passive Na+ transport potassium channels cell volume and intracellular pH changes and calcium channels. 

The NHR contains also the conserved Calcineurin docking site, PxlxIT, required for the physical interaction of NEAT and Calcineurin. Dephosphorylation of at least 13 serines residues in the NHR induces a conformational change that exposes the nuclear localization sequences (NLS), allowing the nuclear translocation of NEAT. Rephosphorylation of these residues unmasks the nuclear export sequences that direct transport back to the cytoplasm. Engagement of receptors such as the antigen receptors in T and B cells is coupled to phospholipase C activation and subsequent production of inositol triphosphate. Increased levels of inositol triphosphate lead to the initial release of intracellular stores of calcium. This early increase of calcium induces opening of the plasma membrane calcium-released-activated-calcium (CRAC) channels,... 

A high sodium intake and increased circulating natriuretic hormone inhibition of intracellular sodium transport, resulting in increased vascular reactivity and a rise in BP and / Increased intracellular concentration of calcium, leading to altered vascular smooth muscle function and increased peripheral vascular resistance. 

Several mechanisms have been postulated to account for thallium s toxicity, including ligand formation with sulfhydryl groups of enzymes and transport proteins, inhibition of cellular respiration, interaction with riboflavin and riboflavin-based cofactors, alteration of the activity of K -dependent proteins, and disruption of intracellular calcium homeostasis. ... 

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