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19 Cards in this Set
- Front
- Back
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When injecting kidney extracts, there is a rise in blood pressure. What is this due to?
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The rise in blood pressure produced by injection of kidney extracts is due to renin. It is an acid protease secreted by the kidneys into the bloodstream.
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How does renin work?
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It acts in concert with angiotensin converting enzyme to form angiotensin 2.
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How is renin synthesized?
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It is synthesized as a large preprohormone. Human preprorenin has 406 amino acid residues. The prorenin that remains after removal of a leader sequence of 23 amino acid residues from the amino ter=minal has 383 amino acid residues. Active renin has 340 amino residues. Prorenin has little biological activity.
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Is prorenin secreted by any other organs?
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It is secreted by the ovaries. prorenin is secreted constitutively, where active renin is formed in the secretory granules of the juxtaglomerular cells, the cells in the kidneys that produce renin.
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What is the only known function of renin?
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To split the decapeptide angiotensin 1 from the amino terminal end of angiotensinogen.
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Where is angiotensinogen found?
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It is found in the alpha 2 globulin fraction of the plasma. It is 13% carbohydrate and is made up of 453 amino acid residues.
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Where is angiotensinogen formed?
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It is synthesized in the liver with a 32 amino acid signal sequence that is removed in the endoplasmic reticulum.
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Do any substances increase its circulating levels?
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Glucocorticoids, thyroid hormones, estrogens, several cytokines and angiotensin 2.
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What is Angiotensin converting enzyme?
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It is a dipeptidyl carboxypeptidase that splits off histidyl-leucine from the physiologically inactive angiotensin 1 forming the octapeptide angiotensin 2.
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In app. 20% of patients on ACE inhibitors, there is a noted cough seen as a side effect. What causes this?
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Increased tissue bradykinin produced when ACE is inhibited acts on Beta 2 receptors to produce the cough.
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Where is most of the converting enzyme found?
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Most of it that forms angiotensin 2 in the circulation is located in endothelial cells. Much of the conversion occurs as the blood passes through the lungs, but conversion also occurs in other parts of the body as well.
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Angiotensin 2, previously called hypertensin or angiotonin, produces arteriolar constriction and a rise in systolic and diastolic blood pressure. TRUE/FALSE
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TRUE. IT is one of the most potent vasoconstrictors known, being 4-8 times as active as norepinephrine on a weight basis in normal individuals.
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The renin in kidney extracts and the bloodstream is produced by the...
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Juxtaglomerular cells. These epithelioid cells are located in the media of the afferent arterioles as they enter the glomeruli.
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Where else in the kidneys is renin found?
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In the Lacis cells. These are located in the junction between the afferent and efferent arterioles.
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Where is the macula densa located?
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At the point where the afferent arteriole enters the glomerulus and the efferent arteriole leaves it, the tubule of the nephron touches the arterioles of the glomerulus from which it arose. At this location, which marks the start of the distal convolution, there is a modified region of tubular epithelium called the macula densa.
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The macula densa is in close proximity to the JG cells. TRUE/FALSE
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TRUE. The Lacis cells, the JG cells and the macula densa make up the Juxtaglomerular apparatus.
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What is Goldblatt hypertension?
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Constriction of one renal aretry causes a quick increase in renin secretion and the development of sustained hypertension(renal or Goldblatt)
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The clinical counterpart of the above condition is renal hypertension due to atheromatous narrowing of one renal artery or other abnormalities of the renal circulation. TRUE/FALSE
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TRUE.
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Many patients with hypertension respond to treatment with ACE inhibitors or losarten even when their renal circulation appears to be normal and even low plasma renin activity. TRUE/FALSE
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TRUE.
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