Refer to the Graphs Below

question 35

Multiple Choice

Refer to the graphs below. Blood vessels constrict in response to the hormone angiotensin.Researchers questioned the roles of elastin and collagen in this response because they are proteins produced and secreted into the extracellular matrix by smooth muscle cells in blood vessel walls.The graphs show protein and mRNA levels corresponding to elastin and collagen in mouse blood vessels under conditions of prolonged angiotensin exposure.Which statement is consistent with these data?

• A) Angiotensin stimulates blood vessel constriction by smooth muscle cells, which signals an inhibition of expression of elastin and collagen genes.
• B) Smooth muscle cells in blood vessels are induced to express their genes for both elastin and collagen in response to angiotensin.
• C) Protein levels of elastin and collagen are raised, but mRNA levels are not affected, suggesting that angiotensin slows protein degradation rates, not gene expression.
• D) Constriction of blood vessels relies on increased levels of elastin but not collagen in the extracellular matrix surrounding smooth muscle cells in blood vessel walls.
• E) Elastin is more important in the relaxation of blood vessels than in their constriction, and collagen is more important in the constriction of blood vessels than in their relaxation.

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