Role of kidney in Electrolyte Balance| RAAS| ADH

  Role of kidney in Electrolyte Balance

Role of kidney in Electrolyte Balance; Osmolality of plasma (moles of solute per kg of plasma) is normally 285 - 295 miliOsmol/kg. The major composition of electrolytes; Na⁺, K⁺, Ca²⁺ and so on.

Regulation of electrolytes is done by mainly 4 pathway:

1.       Renin angiotensin Aldosterone system

2.       Sympathetic nerves

3.       Antidiuretic hormone (ADH)

4.       Atrial natriuretic peptide(ANP)

 RAAS system

 RAAS system

            

Sympathetic nerves

 

•        Nerve terminals in the kidney release norepinephrine.

•        Has 2 direct effect on Na⁺ reabsorption.

• Increase renal vascular resistance: Mostly neutralized by tubuloglomerular feedback.
• Increase Na⁺ reabsorption by tubule cells.
• Stimulate apical Na-H exchanger and basolateral Na-K ATPase pump.

 

 Antidiuretic hormone

• Secreted in response to :
• Increased extracellular fluid osmolarity
• Decreased arterial pressure and
• Decreased blood volume
• Stimulates water reabsorption in CCT by inserting AQP 2.
• Also stimulates Na⁺ reabsorption by stimulating Na⁺ -K⁺ -2Cl ^– pump and increasing Na⁺ channel in collecting tubule.

Antidiuretic

Atrial natriuretic peptide(ANP)

• Produced by atrial myocytes in response to stretch.
• Vasodilation of afferent but constriction of efferent.
• Promotes NaCl and water excretion by the kidney.

Functions of ANP

• Inhibition of renin secretion.
• Inhibition of aldosterone secretion, via Ang II.
• Inhibition of NaCl reabsorption esp. by medullary collecting duct.
• nhibition of ADH secretion and action of ADH on CD.

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