We investigated the diuretic effect of different beverages upon the kidneys considering ions of physiological importance, volume and specific gravity of the urine.Materials and methodIn order to standardise our results we consumed the same food and drink in same quantities on the day of the experiment. Just before drinking our assigned beverage we all urinated to empty our bladders and provide us with a pre-experimental 'base line' reading. We then drank either water, saline, a caffeinated or alcoholic beverage.
The volume consumed was determined by 10ml/kg lean body mass, which equates to about 80% body weight for males. For example, X who weighs _100kg_ would need to drink _800ml_.Once everybody had consumed his or her assigned beverage, quarter hourly urination (where the bladder was fully emptied occurred) followed until 2 hours had elapsed. Volume, specific gravity, potassium, chloride and sodium concentrations were all measured.Volume was measured by pouring the urine into a measuring cylinder.
Specific gravity was measured by placing a small sample of urine on a refractometer. Specific gravity measures the kidney's ability to concentrate or dilute urine in relation to plasma. Because urine is a solution of minerals, salts, and compounds dissolved in water, the specific gravity is greater than 1.0000.The chloride concentration was measured by placing one millilitre of the urine into a chloride meter, set to a standard solution of 100 millimolar. [K+] was calculated by means of a flame photometer.
Urine is sucked into the photometer, and shot as a stream of ions into a carefully controlled flame. The resulting visible spectrum emitted, is compared to the visible spectrum emitted when a solution of known concentrations is sprayed into the same flame. In this investigation the photometer was calibrated to zero using distilled water, and calibrated to 100 using a 100 millimolar standard solution. Therefore, if a solution of potassium was sprayed into the flame, energy will be emitted at a discrete wavelength, which is detected in a phototube to produce a current proportional to the intensity of the light striking it i.e.
the intensity of the emission of K+The same process was repeated for sodium concentration, but a different photometer was used, which was set to and calibrated for measuring sodium. The standard solution for sodium was 100 millimolar.(NB The colour of the flame is pink for potassium (wavelength 766nm) and orange for sodium (wavelength 589nm)).When the urine's ion concentration went beyond the 100mmol scale, we had to dilute the solution by 10 fold by adding one ml of urine to 9ml of distilled water, hence creating a 1 in 10 solution. The result recorded was multiplied by 10 to account for this dilution factor.We repeated our result until all subjects had consumed water, saline, a caffeinated drink and an alcoholic drink.
The average was then calculated. This improves the reliability of our result.We then represented our data as a cumulative frequency graph. This enables the trend to be shown in a clear fashion as well as the total amount of urine secreted during the period of investigation.Sources of Error:1) In standardising what we ate we should have considered our body mass.2) Saline has an emetic effect (i.
e. it can make you sick) therefore it took longer to consume than other drinks such as Carlsberg's special brew.3) It was not always possible to get a urine sample, especially if saline had been consumed.4) Keeping to the 15-minute urination intervals was not always possible, as analysis of the previous sample sometimes overran.5) Each alcoholic drink was investigated only once (unlike the other drinks). i.
e. no repeats.Results and DiscussionLooking at graph 1, the total volume urinated in the two-hour period; the alcoholic drinks created the most urine. As the concentration of alcohol decreases so does the volume of urine. The maximum urine produced was from consuming Carlsberg special brew, which produced 817ml.
The next most diuretic beverage was tea followed by the Tesco beer, which has the least alcohol concentration (3%), and then coffee. Following these was water and then lastly saline which produced 222ml.These results suggest that alcohol act as the most diuretic drinks while saline acts as an anti diuretic. This is shown below on the retention curve.However, strictly speaking alcohol by definition is not a diuretic, as it does not increase sodium concentration in the urine.
However it still gives a diuretic effect by inhibiting the effect of Anti Diuretic Hormone (ADH). ADH acts on the collecting duct by increasing the permeability to water hence increases water reabsorption. The saline solution raises the plasma osmotic pressure; triggering ADH release and therefore reabsorption. If the experiment were to be extended to say 5 hours, the majority of the saline volume would eventually be eliminated.When comparing the concentration of the three physiological important ions - sodium, potassium and chloride, It would seem plausible that the concentration of these ions in the beverage is proportional to the concentration in the urine.
However it is not the case. This is probably because the standardised diet we had has a high level of these ions (probably approaching, if not exceeding our DRV's). Therefore the subjects have to excrete the excess ions in their urine to maintain a stable homeostatic status of these ions in the body. The amount of these ions in the beverages is therefore less significant.We presumed that as we had a standardised diet and our subject's physiology status is similar, we would therefore need to excrete the same amount of these ions in our urine at roughly the same time period.
However the amount of urine we secreted differs due to the different beverages we had drunk which have different diuretic effect on our kidneys.Therefore the concentration of the ions secreted will be affected by the amount of liquid in the urine.The graph above shows the concentration of potassium secreted over 2 hours. Saline produces the most potassium 2407.75 mmol, and most of the alcoholic drinks producing the more dilute concentrations, Smirnoff having 322 millimolar. This correlates, with what was said before, the drinks that have more of a diuretic effect produce a more dilute urine.
The same pattern occurs with the other two ions, but the alcoholic drinks appear in different positions (see below)The ion graphs show the same pattern, and confirm that when more urine is collected, the sample has less concentrated ions. Potassium increases the activity of aldosterone, which decreases the concentration of ions in urine. This explains the results for saline, which contains no potassium, so causing high levels of ions.Finally we will now compare the specific gravity. Smirnoff ice had the highest specific gravity to start with.
From our results the urinary values show that the Smirnoff drinker had the lowest specific gravity. Smirnoff ice's high sugar content and the kidney's 100% efficiency at reabsorbing sugar can explain this difference. Therefore the other drinks must contain chemicals that the body does not want to reabsorb, making the specific gravity of the urine high.
