Final answer:
Dilation of the efferent arteriole can decrease GFR, which in turn could lead to decreased reabsorption in the PCT and reduced renal oxygen consumption. The filtration fraction would also decrease due to an increase in RPF relative to GFR.
Step-by-step explanation:
When the efferent arteriole dilates, it reduces resistance and facilitates blood flow out of the glomerulus. This decreased resistance can lead to a decrease in the glomerular filtration rate (GFR), as there is less pressure to 'push' the filtrate into the nephron. As a result, the proximal convoluted tubule (PCT) reabsorbs fewer solutes and water, primarily because there is less filtrate being produced.
Moreover, since the PCT is responsible for the majority of solute and water reabsorption, any decrease in GFR would generally lead to a reduction in renal oxygen consumption, given that there is less filtrate to reabsorb and subsequently less metabolic activity required. Regarding the filtration fraction, which is the ratio of GFR to renal plasma flow (RPF), efferent arteriole dilation can decrease GFR while increasing RPF, thereby leading to a lower filtration fraction.
Overall, the dilation of the efferent arteriole can subtly modulate kidney function, affecting not just GFR but also the processes of reabsorption and oxygen consumption tied to renal physiology.