Ca2konsentrasjon

Ca2konsentrasjon refers to the concentration of calcium ions (Ca2+) in a solution. In biology and medicine, it is commonly described in millimoles per liter (mM) for extracellular fluids, or as intracellular free Ca2+ concentration, typically in nanomolar (nM) ranges.

Extracellular fluid normally contains about 2.2–2.6 mM total calcium. Resting intracellular free Ca2+ is kept very low, around 50–100 nM, with higher total Ca2+ stored in organelles such as the endoplasmic reticulum and mitochondria.

Ca2+ concentration is measured by several methods. Extracellular levels can be assessed with ion-selective electrodes, colorimetric assays, or spectrometry. Intracellular free Ca2+ is monitored with fluorescent indicators such as Fura-2 or Fluo-4. Total intracellular calcium can be measured by atomic absorption spectroscopy or inductively coupled plasma mass spectrometry (ICP-MS).

Calcium plays essential roles in bone mineralization, muscle contraction, neurotransmitter release, blood coagulation, and as a ubiquitous intracellular second messenger that influences numerous enzymes and pathways.

Homeostasis of Ca2+ is tightly regulated by hormones and organs. Parathyroid hormone (PTH), calcitonin, and vitamin D coordinate renal reabsorption, intestinal absorption, and bone turnover to maintain extracellular Ca2+ within a narrow range. Abnormal Ca2+ levels, hypercalcemia or hypocalcemia, can indicate disease and affect nerves, muscles, and the heart. Diagnosis often requires serum calcium measurements and consideration of albumin binding.

In cellular signaling, Ca2+ acts as a dynamic second messenger. Transient increases in cytosolic Ca2+ trigger signaling cascades that regulate metabolism, gene expression, secretion, and cell survival. Research tools include calcium imaging and pharmacological agents targeting calcium channels and transporters.

---