How does efferent arteriole dilation affect proximal convoluted tubule (PCT) reabsorption, renal oxygen consumption, and filtration fraction?

Efferent arteriole dilation has a significant impact on renal hemodynamics and function. When the efferent arteriole dilates, the resistance in this vessel decreases, leading to a reduction in the pressure within the glomerulus. This decrease in glomerular pressure results in a decline in the glomerular filtration rate (GFR) and ultimately affects various renal functions.

The proximal convoluted tubule (PCT) is primarily responsible for the reabsorption of a substantial portion of filtered sodium, water, and other solutes. With reduced GFR due to efferent arteriole dilation, the overall volume of filtrate entering the PCT decreases. This diminished volume may limit the absolute amount of solute and water available for reabsorption, leading to a decrease in the efficacy of reabsorption.

Furthermore, as the GFR decreases, renal oxygen consumption is likely to decline as well. The kidneys require oxygen to perform various functions, including active transport mechanisms in tubular cells. A lower GFR typically means that there is less renal workload, resulting in reduced oxygen consumption.

Lastly, the filtration fraction, which is the ratio of GFR to renal plasma flow (RPF), tends to decrease with efferent arteriole