It took the diagnosis of high blood pressure (hypertension) at the age of 45 to shock Max into taking better care of himself. A former college football player, he had let himself go, eating too much junk food, drinking too much alcohol, sitting on his chubby bottom for the majority of the last two decades, and even indulging in the frequent habit of smoking cigars. Max’s physician had to prescribe two different antihypertensive medications in order to get his blood pressure under control. She also prescribed regular exercise, a low-salt diet, modest alcohol intake, and smoking cessation. Max was scared, really scared. His father had hypertension at a young age as well, and ended up on dialysis before dying from complications of kidney failure.
Fortunately for Max, he took his doctor’s advice and began a dramatic lifestyle change that would bring him to his present-day situation. Now, at the age of 55, he was a master triathlon athlete who routinely placed among the top five tri-athletes of the same age group in the country. Max’s competitive spirit had been ignited by this, but at the same time he wanted to be first among his peers. To that end, he hired Tracey, a Certified Clinical Exercise Specialist, to help him gain the edge he needed to win at the end of the race. His most immediate concern was that he was experiencing problems with dehydration and fatigue because he hadn’t found an effective way to drink enough fluids while exercising.
Tracey showed Max an impressive array of assessment tools for quantifying and analyzing his physiological state before, during, and after his workouts. One of the tools was urinalysis, which Max found a bit odd, but he dutifully supplied urine samples on a regular, prescribed basis. Tracey explained that Max's hydration status was tricky due to the medication he took to control his hypertension, and that renal status (as measured in the urinalysis) was one of the tools she could use to evaluate his physiological state.
Tracey logs the following results of Max’s urinalysis immediately after, and six hours after, a rigorous 2-hour run.
Time Color Specific Gravity Protein Glucose pH
Before exercise pale yellow 1.002 absent absent 6.0
Immediately after exercise dark yellow 1.035 small amount absent 4.5
Six hours after exercise yellow 1.025 absent small amount 5.0
Short Answer Questions
1. What does the color of Max’s urine tell Tracey about how concentrated or dilute it is? How does Max’s urine color/concentration compare to the urine specific gravity at the same time?
2. Based on the urine color and specific gravity, what might Tracey conclude about the hydration status of Max’s body at the three different times?
3. Antidiuretic hormone (ADH) regulates the formation of concentrated or dilute urine. In which time period is Max’s body secreting its highest amount of ADH? Explain your answer.
4. Tracey knows that proteinuria (protein in the urine) after intense exercise is physiological (normal). However, protein is typically not present in urine. Why is that?
5. Tracey had been slightly concerned about the trace glucose that was found in Max’s urine six hours after his exercise until she discovered that he had eaten an entire large pizza an hour before the urinalysis. Explain why glucose might show up in Max’s urine after a particularly heavy meal.
6. Lactic acid accumulation can be a consequence of intense exercise. Tracey notes that Max’s kidneys are working to defend his body against acidosis. How can she tell? Describe this mechanism.
7. Based on Max’s urinalysis data, should he drink more water prior to exercise to ensure that he doesn’t dehydrate during intense activity? Explain your answer.
8. Max’s regular exercise regimen has reduced his high blood pressure, allowing him to achieve normal blood pressure on a single antihypertensive medication. The medication he takes is called an angiotensin converting enzyme inhibitor, or ACE inhibitor, which blocks the activation of angiotensin II. Describe at least two mechanisms by which angiotensin II targets the kidneys to increase extracellular fluid volume and, therefore, increase blood pressure.
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