AT II Question From Free 150

[Lests55]

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On the Free 150, one of the questions is asking about affects after giving a patient angiotensin II. It asks effects on

1 Plasma Renin
2 Filtration Fraction (GFR/RBF)
3 Efferent Arteriole Resitance

The correct answer is 1 decreases, while 2 and 3 increase. I understand 2 and 3 increasing, but why does 1 decrease? I anticipated with a decrease in RBF you would activate the RAAS?

Thanks

 

[spectrin]

negative feedback

 

[bep207]

You are correct, you do decrease renal blood flow with an administration of AT II. However you have to remember where renin is secreted. Renin is secreted from the JGCs which more or less sense renal blood flow in terms of pressure gradient.
So if you preferentially constrict the efferent arteriole with AT II, you increase the gradient, the push, that the JGCs feel. Therefore renin secretion is decreased because for all the JGCs know the blood pressure is normal or perhaps high.