According to myogenic hypothesis of renal autoregulation, the afferent aerioles contract due to -: (A) NO release, (B) Noradrenaline release, (C) Opening of Ca2+channels, (D) Adenosine release
Answer is C. According to the myogenic mechanism of autoregulation, the rise in aerial pressure stretches the afferent aeriole. Stretch of vascular smooth muscle causes opening of membrane Ca2+ channels. This increases intracellular Ca2+, leading to contraction of the smooth muscle. NO and adenosine:are involved in the TG feedback. They are released by macula densa in response to changes in NaCl in tubular fluids. Norepinephrine:acting a1 receptors located mainly in the afferent aeriole, cause vasoconstriction. Dehydration and strong emotional stimuli (fear, pain) activates sympathetic nerves and reduce RBF and GFR. Prostaglandins (PGs): produced locally within the kidneys during pathophysiologic conditions increase RBF without changing the GFR.