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The collecting duct system of the kidney consists of a series of tubules and ducts that physically connect nephrons to a minor calyx or directly to the renal pelvis.The collecting duct participates in electrolyte and fluid balance through reabsorption and excretion, processes regulated by the hormones aldosterone and vasopressin (antidiuretic hormone).
Aldosterone upregulates epithelial sodium channels in the collecting duct and the colon, increasing apical membrane permeability for Na + and thus absorption. Cl − is reabsorbed in conjunction with sodium cations to maintain the system's electrochemical balance. Aldosterone stimulates the secretion of K + into the tubular lumen. [17]
This increased delivery of sodium overrides the enhanced aldosterone sodium reabsorption at the site of mineralocorticoid action. Moreover, volume expansion, secondary to the action of aldosterone, increases levels of plasma natriuretic hormone and therefore its inhibitory effect on sodium reabsorption in the collecting duct.
In the adrenal cortex, angiotensin II acts to cause the release of aldosterone. Aldosterone acts on the tubules (e.g., the distal convoluted tubules and the cortical collecting ducts) in the kidneys, causing them to reabsorb more sodium and water from the urine. This increases blood volume and, therefore, increases blood pressure.
aldosterone, which stimulates active sodium re-absorption (and water as a result) anti-diuretic hormone, which stimulates passive water re-absorption; Both hormones exert their effects principally on the collecting ducts. Tubular secretion occurs simultaneously during re-absorption of filtrate.
[4] [5] Aldosterone is largely responsible for the long-term regulation of blood pressure. [6] Aldosterone effects on the distal convoluted tubule and collecting duct of the kidney where it causes increased reabsorption of sodium and increased excretion of both potassium (by principal cells) and hydrogen ions (by intercalated cells of the ...
This is e.g. done by endogenous production of aldosterone, increasing reabsorption. Since the normal excretion rate of sodium is ~100mmoles/day, then a regulation of the absorption of still more than 1000 mmoles/day entering the collecting duct system has a substantial influence of the total sodium excreted. [citation needed]
Aldosterone has effects on most or all cells of the body but, clinically, the most important actions are in the kidney, on cells of the late distal convoluted tubule and medullary collecting duct. In the principal cells aldosterone increases activity of basolateral membrane sodium-potassium ATPase and apical epithelial sodium channels, ENaC, as ...