Final answer:
Natriuretic peptides such as ANH and BNP increase GFR by dilating the afferent arterioles and constricting the efferent arterioles, as well as reducing sodium reabsorption in the DCT. They also inhibit aldosterone and ADH release, further increasing urinary excretion of sodium and water and thus regulating blood pressure and volume.
Step-by-step explanation:
Natriuretic peptides, such as atrial natriuretic hormone (ANH) and B-type natriuretic peptide (BNP), play a critical role in regulating the glomerular filtration rate (GFR). This regulation is achieved through several mechanisms:
- ANH, a 28-amino acid peptide, is secreted by the atria of the heart in response to high blood pressure. It increases GFR by dilating the afferent arteriole and constricting the efferent arteriole, leading to increased filtration pressure within the glomerulus.
- Both ANH and BNP reduce sodium reabsorption in the distal convoluted tubule (DCT), which in turn reduces water reabsorption, increasing the volume of urine produced.
- BNP, though having a lower affinity for its receptor, assists in "fine-tuning" blood pressure regulation. Its diagnosis as a marker in congestive heart failure is due to its longer biological half-life.
- By inhibiting aldosterone and antidiuretic hormone (ADH) release, natriuretic peptides reduce sodium and water reabsorption, further contributing to an increase in GFR.
- Overall, the action of natriuretic peptides on the kidney's ability to filter blood is critical for maintaining sodium balance and blood pressure.