You are a physiologist on a space flight to a distant planet. You discover intelligent human-like aliens on the planet. You discover that the alien's kidney handles the sugar alcohol mannitol just like our kidneys handle inulin. The data from that experiment are: Plasma level (constant over 24 hrs): 6 g/dL of mannitol 24 hr. urine sample: volume of 2 L, containing 144 g mannitol What is the alien's glomerular filtration rate (in units of ml/min)

1.67 ml/min

Explanation:

Glomerular filtration rate (GFR) is the best overall index of kidney function, which determines the amount of blood that passes through the glomeruli each minute. Human kidneys can filter the inulin, but they cannot reabsorb or secrete this polysaccharide, thereby it is an excellent substance to measure the Glomerular filtration rate (GFR) by measuring its excretion from the kidneys. In this case, alien´s Glomerular filtration rate (GFR) can be calculated as the excretion rate of mannitol/plasma mannitol level >>>

GFR = 144 g/1 day x 1 dL/6 g x 0.1 L/1 dL = 2.4 L/1 day

GFR = 2,400 ml/1,440 min = 1.67 ml/min

1 and 6 for apex