What happened to the urine concentration as the solute concentration in the interstitial space was increased? how well did the results compare to your prediction?

The answer is that the urine concentration increased (became less dilute). This because of the increased electrolyte concentration in the blood. It causes the hypothalamus-pituitary gland to relead anti-diuretic hormone (ADH). This hormone increases the aquaporin 2 pore in the distal tubules and collecting tubules of the nephrons in the kidneys. Water is reabsorbed from urine hence making it more concentrated.