RBF will show no change because the drug has no effect on total renal vascular resistance. GFR will increase because of a large increase in P(GC). Filtration fraction will, therefore, increase. (Now back up and think a bit more about the GFR: Because filtration fraction increases, there will be a larger than average increase in π(GC) along the glomeruli, and this will offset some of the GFR-increasing effects of the increased P(GC); therefor, GFR will not increase as much proportionately as the P(GC).
