Homeostasis is essential for the human body to regulate and function properly. By achieving appropriate homeostasis levels, the kidneys can differentiate which fluids and how much of each fluid humans should consume. Hormones like Atrial natriuretic peptide (ANP), Antidiuretic hormone (ADH), and Aldosterone each affect osmolarity homeostasis by regulating the kidneys. In order to examine the role of the kidneys in homeostasis, we conducted an experiment to find the highest amount of urine voided after the consumption of a variety of fluids: Gatorade, Coke, water, and no fluids. The experiment tested urine secretion, taking measurements at every 30 minutes for a total of 120 minutes by measuring the total volumes ingested and voided, and by calculating urine flow rates, urine specific density, and urine pH. We predicted Gatorade drinkers would produce higher volumes of urine compared to the groups drinking Coke. What we found was that the highest urine voided group was the water drinkers and lowest was the coke drinkers. The results did support our hypothesis, the highest urine voided group was the water drinking group as we predicted, followed by Gatorade drinkers, Coke drinkers, and finally non-drinkers. The less acidic, more pH neutral, and less sodium concentrated drinks produced the highest urine voids.
Introduction
Homeostasis is essential for the human body to regulate and function properly. It regulates body fluids which is significant since the majority of chemical reactions via enzyme proteins are dependent on the proper levels of fluid pH. Proton transport across the plasma membrane cannot happen without the proper modulation of the intracellular pH, a result of homeostasis in pH. Achieving concurrent homeostasis levels in the kidneys could help differentiate which type of fluids and the optimal amount humans should consume to produce the maximum results during any and all activities.
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The kidney functions by the use of many nephrons which filter the blood and remove waste. Each nephron begins its process of filtration from the afferent artery moving the blood into the glomerulus where it is filtered and then pushed into the Bowman's capsule. From there the filtrate enters the proximal tubule where the reabsorption of ions and amino acids into the bloodstream occurs while simultaneously secreting all the waste from the bloodstream into the proximal tubule. The filtrate then passes through the loop of Henley, altering the concentration of the filtrate before entering the collecting duct to be voided (Widmaier, E., Raff, H. & Strang, K., 2015). The level of concentration reached when in the collecting duct determines the concentration of the soon-to-be voided urine.
Maintaining kidney osmolarity homeostasis is crucial for the proper regulation [absorption/secretion] of water from the body. The kidney uses a countercurrent flow system in order to maintain homeostasis. In its steady state phase, the blood osmolarity is 300 mOsm/liter and the osmolarity increases to 1200 mOsm/liter as solutes concentration increases (Widmaier, E., Raff, H. & Strang, K., 2015). Hormones like ANP, ADH, and Aldosterone all function to regulate and manufacture homeostasis. ANP reduces sodium reabsorption by inhibiting the cyclic nucleotide-gated cation channels, the epithelial sodium channel, and the heteromeric channel transient receptor potential-vanilloid 4 and -polycystin 2 and diminishes vasopressin-induced water reabsorption (Theilig, F. & Wu, Q., 2015). ADH causing the body to retain water, thus decreasing blood osmolarity when urine concentration is high. The hormone Aldosterone causes an intake of water and sodium into the blood to increase blood pressure and osmolarity when needed. High levels of osmolarity concentration lead to high levels of urine concentration meaning a large number of solutes and less water in the urine.
In order to examine the role of the kidneys in homeostasis, we experimented to find the highest amount of urine voided after the consumption of a variety of fluids: Gatorade, coke, water, no fluids. The experiment tested urine secretion for 2 hours at every 30 minutes by measuring the total volumes ingested and voided, and by calculating urine flow rates, urine specific density, and urine pH. We hypothesized that the consumption of water would produce the largest amount of urine secreted, yielding the highest urine flow rates, lowest specific density and having the most neutral pH of all the groups.
Methods
Subjects came fasted for 5 hours prior to the experiment. The first void, T=0, all subjects are to utilize 2 urinary cups to empty their bladder completely. All groups are to measure and calculate the density, flow rate, specific gravity, and test the urine sample, for traces of blood, ketones, proteins, and glucose.with the use of a labstix strip, drinking groups will set aside T=0 sample to analyze later. The groups who consume liquids will consume the specified amount of liquid that was calculated. The amount of fluid to consume is calculated by the formula: volume of fluid intake(ml) = [body weight (lbs.) x 7mL/lb.] x 0.80 (Manuguid, C., et al. 2019) . Specific density is calculated by multiplying the last 2 digits of the corrected urine specific gravity multiplied by 2.66 g/L. Urine flow rates are calculated by dividing the volume voided (ml) by the duration of time from current to prior void (min). The same steps and calculations were the specific gravity, urine flow rate, and density is measured and calculated will be repeated for intervals a total of 120 minutes, the subject is to collect a void at every 30-minute interval following T=0 void.
Discussion
The purpose of this study was to measure the effects of four different fluids on urine concentration, volume voided, and osmolarity homeostasis. Prior to the start of the lab, the subject fasted for five hours to record optimal results. The first void T=0 was conducted prior to the start of the experiment. Void T=0 was used to measure whether the subject had fasted for the required hours. We used a Labstix to test for any traces of blood, ketone, glucose, and protein in the urine. The subjects drank a specific amount of liquid based by a calculation in accordance with their body weight. The liquids used in the experiment were Coke, Gatorade, water, and a group were given no liquid to drink. The subjects voided at intervals of approximately 30 minutes for a period of 120 minutes. We measured from the voids was the volume voided, urine flow rate, temperature, specific density, and pH. The objective was to test which group would void the most. We predicted that the subjects who drank water would produce the largest amount of urine voided and Gatorade drinkers would produce more urine than coke drinkers since hormones like ANP which inhibition of net salt and water reabsorption in the cortical and inner medullary collecting ducts (Zeidel, M., 1990) leading to higher levels of water excretion compared to Coke-drinkers where coke increases the osmolarity concentration and water retention .
The results were in agreement with our hypothesis. The highest urine voided group was the water drinkers with 704 ml being their highest amount voided. The Gatorade drinkers group had the second highest amount voided at 652 ml. Following the Gatorade drinkers, Coke drinkers who had their highest volume voided at 403 ml. The non-drinkers group had the least volume voided at 131 ml. The order in volume voided fell in line with our predictions as water drinkers had the highest and non-drinkers produced the least urine voided. In a similar study, it was found that higher sodium excretion rests only on changes in urinary sodium concentration (Bankir, et al. 2017). This helps explain why coke drinker had a higher specific density and more urine secreted at T=30 but dropped, back to normal, lower than other fluids [gatorade and water] as the experiment continued. The subjects continuously increasing their urine intake like other fluid-drinking groups but did not excrete at the same, increased volumes as the water and Gatorade-drinking groups. The urine flow rate of water drinkers peaked at 8.91 ml/min and Gatorade drinkers’ urine flow rate peaked at 9.21 ml/min yet, both produced very similar numbers. The non-drinkers group had their highest point at the first interval, T=30, then produced at a constant decrease. Coke drinkers numbers increased to the time interval of T=90. Non-drinkers had the highest specific density while the water drinking group acquired the lowest specific density. PH levels remained within the 6 to 6.80 range for all groups. The Non-drinkers and water drinkers had more neutral pHs while the coke drinkers group outcome showed pH levels of 6.07. The Gatorade drinkers group had a pH of 6.54.
At the end of the experiment, water drinkers had the highest flow rate posing results closer to 6 ml/min followed by Gatorade drinkers then coke drinkers who’s flow rate showed numbers closer to 4 ml/min. Non-drinkers had the lowest flow rate at T=120, with a difference of more than 3 ml/min between non-drinkers and the next group. The reason that there was not a significant difference between all the different drinking groups but there was between the drinking and non-drinking groups ws dehydration. In a similar study testing the effect on hydration of two diets: one with and one without plain water, it was found that plain drinking water compared to exclusion of plain drinking water in the diet did not affect hydration (Grandjean, A. et al., 2003). The urine specific density at the end of the experiment, T=120, however, showed opposite results compared to the flow rate. Non-drinkers produces the highest specific density followed by coke drinkers, then Gatorade drinkers and lastly water drinkers. This is due to dehydration and having a higher concentration of solutes in the kidneys, which is why water-drinkers had the lowest specific density. As expected the pH of water drinkers and on-drinkers was very similar at T=120.
The results support our hypothesis regardless of any errors in measurements that could have taken place. Possible errors include incorrect readings of urinometer, unsubstantial fast duration, and loss in urine collected in void cups when urinating at each interval. The highest urine voided group was the water drinkers and lowest was the coke drinkers. Though there were some subjects who did not fast correctly or entirely, the results did go as we predicted, water drinkers would produce the most urine voided followed by Gatorade drinkers, then Coke drinkers, and finally non-drinkers. We see that there is a relation between the types of drinks one intakes to their urine output. The less acidic, more pH neutral, and less sodium concentrated drinks produced the highest voids. In a similar study testing the relationship between sodium and water intake, found that after an increase in sodium intake, fluid intake is increased for the first couple days, but the urine volume does not increase (Bankir, et al. 2017). The extra fluid drunk is responsible for an increase in body weight. We can use this knowledge for future studies. Were these same methods can be applied however done more more accurately by measuring the height, weight, waist circumference, body protein content, and percent body fat mass of subjects (Zhang, N., et al. 2017) and done for a longer period to to test other types of fluids consisting of high and low volumes of sodium, in comparison to water to see if other fluids will pose the same results.
References
- Bankir, L., et al. (2017). Relationship between Sodium Intake and Water Intake: The False and the True. Annals of Nutrition and Metabolism,70(1), 51-61. doi:10.1159/000463831
- Grandjean, A. C., et al.(2003). The Effect on Hydration of Two Diets, One with and One without Plain Water. Journal of the American College of Nutrition,22(2), 165–173.
- Manuguid, C., et al. (2019). Biology 613 Human Physiology Lab Manual (pp. 64-66). San Francisco: San Francisco State University.
- Perrier, E. T., Buendia-Jimenez, I., Vecchio, M., Armstrong, L. E., Tack, I., & Klein, A. (2015). Twenty-four-hour urine osmolality as a physiological index of adequate water intake. Disease markers, 2015, 231063.
- Rakova, N., et al. (2017). Increased salt consumption induces body water conservation and decreases fluid intake. Journal of Clinical Investigation,127(5), 1932-1943. doi:10.1172/jci88530
- Theilig, F. & Wu, Q. (2015). ANP-induced signaling cascade and its implications in renal pathophysiology. American journal of physiology. Renal physiology, 308(10), F1047-55.
- Widmaier, E., Raff, H. & Strang, K. (2015) Vander’s Human Physiology: The Mechanisms of Body Function. Boston: McGraw-Hill Higher Education. Print
- Zeidel, M. (1990). Renal Actions Of Atrial Natriuretic Peptide: Regulation Of Collecting Duct Sodium And Water Transport. Annual Review of Physiology, 52(1), 747-759. doi:10.1146/annurev.physiol.52.1.747
- Zhang, N., et al. (2017). Hydration, Fluid Intake, and Related Urine Biomarkers among Male College Students in Cangzhou, China: A Cross-Sectional Study-Applications for Assessing Fluid Intake and Adequate Water Intake. International journal of environmental research and public health, 14(5), 513. doi:10.3390/ijerph14050513
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