What would happen to the glomerular capillary pressure and filtration rate?

Question

What would happen to the glomerular capillary pressure and filtration rate if you increase the diameter of the afferent arteriole?

If, experimentally, the solute concentration of the medullary interstitial fluid of the kidney is increased; what would happen to the urine volume and concentration?

Answer 1

Tubuloglomerular Feedback Mechanism: If you increase the diameter of your afferent arteriole, assuming all other factors remain the same, you will increase your renal blood flow delivered to your glomerulus. This will increase your capillary hydrostatic pressure, and ultimately increase your glomerular filtration rate.

Your second question asks about solute concentration in the interstitial fluid of the kidney... so, I suppose you're talking about the countercurrent multiplier in the Loops of Henle. If you increased the concentration of your interstitial fluid (I think you're talking about the medullary concentration gradient), you would have the ability to concentrate urine (tubular fluid) more throughout the nephron (chiefly in the Loops of Henle -- ascending and descending have different permeability to solutes and water). There's much more on this topic, though. This is an extremely cursory answer.