Final answer:
Autoregulation of glomerular filtration rate involves changes in the afferent arteriole, juxtaglomerular cells responding to paracrine signals, and mesangial cells, making the correct answer all of the above.
Step-by-step explanation:
Autoregulation of the rate of glomerular filtration involves multiple mechanisms including changes in the afferent arteriole, the juxtaglomerular cells which respond to paracrine signals, and the actions of mesangial cells. The afferent arteriole displays a myogenic mechanism, where increased blood pressure causes the smooth muscle cells to contract, thereby resisting increased blood flow and maintaining a relatively constant glomerular filtration rate (GFR).
The tubuloglomerular feedback mechanism, involving the Juxtaglomerular Apparatus (JGA) and macula densa cells, responds to changes in the fluid flow rate and Na+ concentration in the distal convoluted tubule (DCT). These cells release ATP and adenosine, which cause the afferent arteriole to constrict or dilate, thus adjusting GFR. Additionally, the mesangial cells can also alter blood flow and filtration by contracting. Therefore, the correct answer to the question is D) all of the above.