Ca2Aufnahme

Ca2Aufnahme refers to the process by which calcium ions (Ca2+) are transported into cells or into intracellular storage compartments. It is a central aspect of cellular signaling and homeostasis, influencing muscle contraction, neurotransmitter release, enzyme activity, and gene expression. Calcium uptake occurs across the plasma membrane and into organelles such as the endoplasmic reticulum and mitochondria.

Across the plasma membrane, Ca2+ enters through various pathways. Voltage-gated calcium channels respond to membrane depolarization, while receptor-operated channels and store-operated calcium entry provide Ca2+ influx in response to signals or depletion of ER stores. TRP channels also contribute to Ca2+ permeation. The cytosolic Ca2+ concentration is kept low by pumps and exchangers that move Ca2+ out of the cell, ensuring a steep gradient for uptake.

Intracellular organelles also take up Ca2+. The endoplasmic reticulum and sarcoplasmic reticulum sequester Ca2+ via SERCA pumps, regulating cytosolic levels and enabling rapid release during signaling. Mitochondria accumulate Ca2+ through the mitochondrial calcium uniporter (MCU) complex, where Ca2+ influences metabolism and apoptotic pathways.

Physiologically, Ca2Aufnahme in epithelia supports absorption and reabsorption. In the intestine, transcellular Ca2+ uptake involves TRPV6 channels and calbindin, under vitamin D control. In the kidney, Ca2+ reabsorption is mediated by transporters in the proximal tubule and distal nephron, modulated by hormones such as parathyroid hormone and calcitriol.

Dysregulation of Ca2Aufnahme can contribute to disorders including hypocalcemia, hypercalcemia, arrhythmias, and skeletal diseases. Experimental approaches to study Ca2+ uptake include radiolabeled calcium flux assays and fluorescent Ca2+ indicators.