USMLE Step 1 Renal Physiology Review 59 16 Renin

USMLE Step 1 Renal Physiology Review 59 16 Renin

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Play USMLE Audio MP3   59 16 Renin Below

Begin   59 16 Renin Transcription

Now let’s talk about the renin-angiotensin system. What structure is between the afferent arteriole and the distal convoluted tubule where they come together? It starts with JA.

  • The juxtaglomerular apparatus.

In the juxtaglomerular apparatus what are the cells on the afferent arteriole called?

  •  Juxtaglomerular cells.

What is on the distal convoluted tubule? It starts with MD.

  • The macula densa is on the distal convoluted tubule.

What type of cell is the juxtaglomerular cell?

  • The juxtaglomerular cell is a modified smooth muscle cell.

What enzyme do the juxtaglomerular cells secrete? It starts with an R.

  • Renin.

How do the juxtaglomerular cells secrete renin?

  • Pro-renin is split within the cell and the renal is released.

What structre stimulates renin secretion?

  • The macula densa stimulates renin secretion.

What does the macula densa respond to?

  • Low sodium in the urine.

What are two other things that stimulate the release of renin?

  • One has to do with blood volume and the other with the afferent arteriole. Lowered blood volume and lowered arterial blood pressure in the afferent arteriole also stimulate the release of renin.

What substrate in the blood does renin work on? It starts with an A.

  • Angiotensinogen.

What kind of compound is this?

  • Angiotensinogen is an alpha-2 globulin.

What organ produces angiotensinogen?

  • The liver.

Renin acts for how long?

  • Renin acts for 30 to 60 minutes.

What does it convert angiotensinogen into?

  • Angiotensin I.

And then what is angiotensin I converted into?

  • Angiotensin II.

Where does this happen?

  • Angiotensin I is converted into angiotensin II in the lungs.

By what lung cells?

  • The endothelium of lung capillaries.

Utilizing what enzyme?

  • Angiotensin-converting enzyme or ACE.

Although it is primarily found in lung tissue, name two other places where angiotensin-converting enzyme is present to a lesser degree.

In the kidneys and in blood plasma.

Student doctor, please pause the tape and summarize what we’ve discussed about the juxtaglomerular apparatus, renin secretion, angiotensinogen, and the formation of angiotensin I and II.

The juxtaglomerular apparatus is between the afferent arteriole and the distal convoluted tubule where they come together. The juxtaglomerular cells which are on the afferent arteriole are modified smooth muscle cells that secrete the enzyme renin. Pro-renin is split within the cell and renin is released. The macula densa which is on the distal convoluted tubule is also part of the juxtaglomerular apparatus and stimulates renin secretion in response to low sodium in the urine. The release of renin is also stimulated by lowered blood volume and lowered arterial blood pressure in the afferent arteriole. Renin, which acts for 30 to 60 minutes, converts the substrate angiotensinogen, an alpha-2 globulin produced by the liver into angiotensin I. This in turn is converted into angiotensin II in the lungs by the endothelium of lung capillaries utilizing angiotensin-converting enzyme or ACE. Although this enzyme is primarily found in lung tissue it is present to a lesser degree in the kidneys and in blood plasma.

 

 


 

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