Animal Endocrine Pancreatic Physiology - Lab Report Example

APPLIED ANIMAL PHYSIOLOGY Name Class Professor University City, State Date Contents 1.Aim 3 2.Materials/Methods 3 3.Result 4 4.Discussion 6 Conclusion 8 Bibliography 9 1. Aim There are a number of experiments developed to establish glucose metabolism. The standard test for the pancreases to secrete insulin is the glucose test (Ferrannini & Pilo, 1979). The aim of the experiment was to introduce the concept of Intravenous Glucose Tolerance Test (IVGTT), hence demonstrate how the pancreases of a sheep respond to a glucose load. Additionally, the practical aimed at determining the influence of different nutritional planes on IVGTT results. The clearance rate for a given load of glucose is directly proportional to the secretion of insulin and hence indicates the ability of the pancreas to respond to hyperglycemia by secreting insulin. 2. Materials/Methods Each student group was provided with the following materials; a sheep with an indwelling venous catheter and safe-site port, syringes, needles and heparin saline as well as glucose solution (50% w/v). Also issued at the class level were advantage Glucose Meter and Advantage II glucose detection strips. The practical involved two different treatments. Three sheep fed on a cereal grain-based diet that is high plane on nutrition and three on roughage low on nutrition. Different groups worked on each of the six sheep by conducting an IVGTT. The sheep received an injection of 0.4 g/Kg (live weight) glucose intravenously in the form of 50% glucose solution for a period of about 1 to 2 minutes. We took blood samples before and after the injection. Each group through the indwelling intravenous Cather’s did collection of blood from the sheep. We noted the diet the sheep fed on. The collection of blood involved injecting a 5 ml syringe containing heparanized saline to the safe-site port. To ensure that fresh blood was in the Cather, we withdrew a dead space from the Cather tube. For uninterrupted blood flow, we moved sheep’s head in case the tubing pressed itself against something inside the sheep. Additionally, an injection of heparanized saline into the Cather cleared any clots that may have occurred, and then syringe withdrawal followed. We withdrew the 5 ml syringe containing a mixture of blood and heparanized saline following the Cather being full of fresh blood, and then attached a collection of 2ml blood. We withdrew the blood into the syringe and a 5ml syringe full of pure heparanized saline attached to the safe-port. We recorded time of withdrawing the blood. An injection of 1 to 2 mills of heparanized saline into the Cather followed to ensure that the tube had no blood. We then removed the syringe. From the main menu bar, we selected “Run Glucose Test” and inserted glucose detection strip when we received a prompt command. To avoid disruption of future tests we closed the container of the detection strips within 30 seconds. Another prompting led to the use of a Pasteur pipette to withdraw blood from the heparin zed tube and a sufficient single drop of blood placed inside the yellow notch on detection strip. A touch on the drop of blood to the yellow strip made it flow across the yellow area covering it completely. We took a measurement of the blood glucose from the glucose meter. 3. Result The study of insulin secretion and glucose elimination was in six sheep of which three were under high nutrition diet and the other three under low nutrition diet. We injected 0.4g/Kg glucose intravenously in the form of 50% glucose solution in a period of 1 to 2 minutes. Then we took blood samples before and after the glucose injection at 0, 1, 5, 10, 20, 50, and 75 minutes. Plasma glucose increased significantly during the 75 minutes IVGTT in the sheep fed on high nutritional diet compared to the low nutritional diet. Glucose tolerance as assessed by the glucose elimination constant Kg was significantly affected in both diet treatments. Insulin secretion varied significantly between the nutritional diets. Although insignificant, high nutritional diet sheep had a lower acute insulin response than the low nutritional diet. The AUC for insulin was similar between the two nutritional diets during the IVGTT, however, insulin in the high nutrition diet was lower at 10, 20, 30, 40, 50, 60, and 70 minutes compared to glucose at the same timing. We arrived at the relationship between glucose injection and insulin increment using an equation where insulin secretion rate is a function of the rate of change of glucose and its concentration. Two assumptions formed the basis of our calculations. First, the rate of insulin is assumed to be related to glucose concentration and second is that the controls were at intervals of time to account for the fact that secretion of insulin is directly proportional to glucose concentration but with some delays. The figures below represent the glucose elimination from the sheep’s blood. The first one shows the glucose concentration during the IVGTT while the second represent area under the curve fro glucose from zero to 75 minutes after the injection of glucose. During IVGTT, the production of insulin in the sheep on high nutritional diet was lower and glucose took long to exit from their blood. The insulin secretion increased rapidly within the first 10 minutes then reduced. The figures below represent insulin concentration during IVGTT and the incremental area under the curve for insulin from zero to 75 minutes after glucose injection. 4. Discussion Although there are many studies in the literature, there is insignificant information on ruminants and other animals regarding glucose homeostasis in gastrointestinal tracts. It is also unknown whether this trend changes or remains constant with the injection of glucose. Somehow, analytical and technical challenges in the existing researches limit such information. Therefore, we conducted practical using accurate, efficient, and sensitive methods of blood collection and detection tests. In this case, we used intravenous glucose tolerance test (IVGTT), which is the best-established method of measuring insulin resistance. The aim of the practical was to determine an IVGTT that lasts 75 minutes. The test was labor intensive and based the analysis of data on insulin response and the rate of glucose metabolism. We calculated the relationship between glucose injection and insulin increment using an equation where insulin secretion rate is a function of the rate of change of glucose and its concentration. Two assumptions formed the basis of the calculations. First, the rate of insulin is assumed to be related to glucose concentration and second is that the controls were at intervals of time to account for the fact that secretion of insulin is directly proportional to glucose concentration but with some delays. The area under the curve for insulin was similar between the two nutritional diets during the IVGTT, however, insulin in the high nutrition diet was lower at 10, 20, 30, 40, 50, 60, and 70 minutes compared to glucose at the same timing. The insulin secretion in response to the glucose challenge was not different between the high nutritional diet and the low nutritional diet but it was significantly higher after glucose injection. These results indicate that feeding a high nutrition diet to sheep reduces sensitivity to insulin in relation to a relatively low nutritional diet. During IVGTT, the production of insulin in the sheep on high nutritional diet was lower and glucose took long to be eliminated from their blood, though it did not reach statistical value (p=0.069) (Roden, 2007). These results indicated that the rate of clearance of the injected glucose is directly proportional to the rate of insulin secretion. This is true since insulin affects the rate of absorption of glucose into cells. The data represented indicates that a sharp rise in insulin concentration to the maximum follows an injection of glucose. Then a pulsating secretion follows approximately 25 minutes later. An assumption from this observation is that insulin secretion depends on glucose concentration and exchange rate, and simulation of the subject’s pattern during an IVGTT done within the first 25 minutes after glucose injection. A scientific challenge raised during the practical is that blood dilution is likely to affect the relationship between the concentration of glucose and insulin measured during IVGTT. Erroneous results are likely to occur during early stages of IVGTT. These affect the glucose and insulin concentration. Additionally, the plot of glucose increment against time indicated a shoot within the first few minutes after IVGTT initiation. This led to higher glucose concentration. The overshoot is inconsistent and detailed analysis on the same is impossible. Another challenge of this practical is that all subjects used were under normal conditions, no sheep with a disease like diabetes that affect glucose metabolism was included (Roden, 2007). Diabetic subjects could have shown even higher insulin increment than the sheep used in the practical. Finally, there were no hemodynamic measurements made, which could have resulted in better presentation. Conclusion Glucose metabolism and insulin secretion examined in sheep is in response to an injection of glucose through an indwelling intravenous Cather into the safe-site port. T The aim of the experiment was to introduce the concept of Intravenous Glucose Tolerance Test (IVGTT), hence demonstrate how the pancreases of a sheep respond to a glucose load. Additionally, the practical aimed at determining the influence of different nutritional planes on IVGTT results. The results indicated that different nutritional diets affected insulin secretion. In addition, insulin increment is directly proportional to glucose concentration. Bibliography Ferrannini, E. & Pilo, A. (1979). Pattern of Insulin Delivery after Intravenous Injection in man and its Relation to plasma glucose Disappearance. Journal of Clinical Investigation. Vol. 64(1), 243-254. Roden, M. (2007). Clinical diabetes research methods and techniques. Chichester, West Sussex, England, John Wiley & Sons. http://site.ebrary.com/id/10297841. Read More