Reninfrisättning

Reninfrisättning refers to the process by which the enzyme renin is released into the bloodstream. Renin is primarily produced by specialized cells in the juxtaglomerular apparatus of the kidneys. This release is a crucial step in the renin-angiotensin-aldosterone system (RAAS), a hormonal cascade that regulates blood pressure and fluid balance.

Several factors can trigger renin release. A significant stimulus is decreased blood flow to the kidneys, which can occur due to low blood pressure or volume depletion. Baroreceptors in the afferent arterioles of the juxtaglomerular apparatus detect this reduction and signal for renin secretion. Another mechanism involves macula densa cells in the distal tubule, which sense low sodium and chloride levels in the tubular fluid. When these levels are low, it indicates reduced glomerular filtration, prompting renin release.

Sympathetic nervous system activation also stimulates renin release through beta-1 adrenergic receptors on juxtaglomerular cells. This response is often activated during stress or exercise. Once released, renin acts on angiotensinogen, a protein produced by the liver, cleaving it into angiotensin I. Angiotensin I is then converted to angiotensin II by angiotensin-converting enzyme (ACE), which plays a central role in vasoconstriction and aldosterone release, ultimately increasing blood pressure.