You are a physiologist on a space flight to a distant planet. You discover intel

Question

You are a physiologist on a space flight to a distant planet. You discover intelligent humanoid aliens inhabiting the planet, and they willingly submit to your tests. You discover that the alien’s kidney handles the sugar alcohol mannitol just like our kidneys handle inulin. You also test the alien for its renal handling of glucose. The data from the experiment are: plasma level (constant over 24 hrs.): 6 g/dL of mannitol and 2 g/dL of glucose. 24 hr. urine sample: volume 2 L, containing 144 g mannitol and 52 g glucose. (dL is 100 ml)

                A. What is the alien’s glomerular filtration rate?

                B. What is the alien’s clearance rate for glucose?

                C. How does the alien kidney handle glucose?

Explanation / Answer

By using the excretion rate of mannitol in the urine, we can calculate the GFR=144g/dayx1dL/6gx0.1L/1dL= 2.4 L/day

The alien clearance rate of glucose=GFR X Plasma concentration of glucose=(2.4 L/day)x(2g/dL)x(1dL/0.1L)=48g/day

The normal clearance rate of human kidney is 162 g of glucose/day, but here the alien kidney is clearing only 48 g/day. The alien kidney handling glucose is different from us and it is not losing much water into urine.

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