Active Transport, Hematology, EKG and Urinalysis Author: Margaret T. F

FINAL PROBLEM SET: Integration of Material from 4 Labs; Active Transport, Hematology, EKG and Urinalysis

Author: Margaret T. Flemming, MS, Department of Biology, Austin Community College, Austin, TX

Objectives—after completing this problem set you should be able to: 1) calculate renal function values, showing your work 2) describe the relationship between cardiac and renal function 3) describe the relationship between blood values and urine values, including relevant information regarding secondary active transport of glucose by the renal tubules

Background—Renal function calculations can give a good snapshot of a patient’s health, indicating possible circulatory problems, blood glucose problems, etc. But being able to do the calculations is only the first step. This problem set asks you to do calculations and then think critically to analyze results and come up with possible diagnoses.

To successfully answer the critical thinking questions you will need to integrate what you know about renal function, active transport, and normal blood and urine values. In addition, you’ll need to bring in what you know about normal cardiac output (CO), renal fraction of CO and how the kidney adjust to changes in CO and blood pressure.

Resources—Work in your regular lab groups of 3-4 students. Definitions and formulas are given to you, along with certain clinical values that were not obtained in labs. Chapters 5, 15 and 16 and 19 in your text (Human Physiology, Silverthorn, 4th Ed.), as well as in your notes for those chapters, provide the background information needed to answer the theoretical questions. Remember to limit your online searches to sites ending in edu, or sites of professional organizations, rather than commercial sites.

Part I: Your personal calculations can be done using the data obtained from the Hematology Lab (Lab 6), the EKG Lab (Lab 8) and the Urinalysis Lab (Lab 11). Fill in your personal values in the table

©2007 Margaret T. Flemming below, and then calculate the renal function values, using the definitions and formulas provided. Problem 1 source of data: value (include units) your value from lab V (urine flow) your value from lab Hct your value from lab resting HR your value from lab Exercising HR given stroke volume female = 65 ml/beat male = 75 ml/beat calculate from CO a. show work below above given renal fraction 20% calculate renal blood flow b. show work below calculate renal plasma c. show work below flow given Pglucose 100 mg / dL given GFR female = 115 ml/min; male = 125 ml/min calculate filtered load for d. show work below glucose Data table courtesy of Sarah Strong Problem 1. Show your work here: a.

e. The following question may seem straight forward, but isn’t, so think carefully. What change in renal blood flow would you expect from the changes in your exercising heart rate? Explain your answer.

©2007 Margaret T. Flemming Definitions and formulas: definition formula renal fraction amount of CO that goes through the kidney [ml/min] renal plasma flow amount of plasma that goes (urine PAH)(urine flow) ÷ through the kidney [ml/min] plasma PAH filtration fraction fraction of renal plasma flow that GFR ÷ renal plasma flow becomes glomerular filtrate glomerular filtration rate of filtrate formation [ml/min] inulin clearance rate (GFR) plasma load total amount of a substance in (renal plasma flow) X the plasma that passes through (plasma concentration) the kidney each minute [mg/min] filtered load total amount of a substance (GFR)(Px) entering the tubules each minute [mg/min] clearance volume of plasma completely Ux * V ÷ Px (RC or CLx) "cleared" of substance x in a given period of time [ml/min] transport maximum maximum rate of transport of (GFR)(Px) - UxV (Tmx) substance across the kidney tubules [mg/min] renal threshold Tm ÷ GFR courtesy of Sarah Strong

Abbreviations: Px = plasma concentration of substance x Units: (mg/ml) Ux = urine concentration of substance x Units: (mg/ml) V = urine volume per unit time Units: (ml/min) Clx = clearance of substance x Units: (ml/min) Tmx = transport maximum for substance x Units: (mg/min) GFR = glomerular filtration rate Units: (ml/min) Hct = hematocrit (% of volume of blood made up of cells) HINTS: 1. find the right formula (if you need one) 2. write out the formula including units 3. do any conversions required to get the right units 4. do the math 5. check the units

a. Assume your GFR is "average" for your sex and age. Calculate Tubular Load for Glucose, using the formula below. Young adult males: GFR = 125 ml/min Young adult females: GFR = 115 ml/min

Tubular Load for Glucose = GFR x Pxglucose

b. Based on the information above AND the results of your urinalysis test for the presence of glucose in your urine, what can you infer about your tubular load of glucose compared to the Tmglucose? Before answering this question, read the discussion of transport maximum in the textbook.

Possible Answers: x. Your tubular load of glucose is greater than the transport maximum. y. Your tubular load of glucose is less than the transport maximum. z. Your tubular load of glucose is equal to the transport maximum.

Explain your answer.

PART II: Using patient data

Problem 3: Mary had been concerned about her 8 year old son Robin. Although a typically active boy, he had been constantly hungry and thirsty and yet was losing a little weight and was urinating frequently. You are given the following patient information. GFR = 125 ml/ min plasma concentration of glucose = 500 mg/dL urine flow = 2.5 ml/min urine concentration of glucose = 120 mg/ml

a. Calculate Robin’s filtered load for glucose:

b. What is wrong with Robin? Explain your conclusion.

©2007 Margaret T. Flemming Problem 4: George is a 43 year old male in good health. He had recently moved to a new town, was ready for an annual physical and contacted the one his friend recommended. After a thorough check, the doctor sent off blood and urine samples and got the following results:

Plasma inulin conc. 0.30 mg/mL Plasma PAH conc. 0.02 mg/mL Urine inulin conc. 7.50 mg/mL Urine PAH conc 2.64 mg/mL Plasma glucose conc. 100.00 mg/dL Urine flow rate 5.00 ml/min Urine glucose conc. 1.00 mg/mL Blood hematocrit 46%

a. What is George’s glomerular filtration rate?

b. What is George’s glucose clearance?

c. What is George’s rate of tubular reabsorption of glucose? [Hint: think about Tm.]

d. The doctor was a little confused and wondered does George have diabetes? Explain your answer in terms of tubular cell transport functions.

e. What values above and what formula would you use to calculate George’s Renal Plasma Flow?

Eaton, D.C., Pooler, J.P. Vander’s Renal Physiology. Lange Medical Books/McGraw-Hill, 2004.

Ganong, William F. Review of Mediacl Physiology, 21st ed. Lange Medical Books/McGraw-Hill, 2003.

Silverthorn, Dee Unglaub. Human Physiology: An Integrated Approach, 4th ed. Pearson Benjamin Cummings, 2007.