STZ Effects on HA Production and HAS Expression in Channel Catfish Through Liver Damage

My research project is primarily focused on how different doses of a chemotherapy drug, Streptozotocin (STZ), affect channel catfish. This drug has been commonly used to treat pancreatic tumors and induce hyperglycemia, or high blood sugar, in rodents. We are using channel catfish as alternative model organisms for investigating human metabolic disorders such as obesity and diabetes because these fish have an accelerated growth rate similar to the phenotype observed in obese and diabetic patients. However, administering STZ into channel catfish has been shown to display the opposite effect, resulting in a high mortality rate and hypoglycemia, or low blood sugar. Abnormal morphology of the liver and gall bladder has also been noted in past studies, possibly indicating liver damage associated with the STZ treatments. However, the exact mechanism(s) associated with the development of hypoglycemia and liver damage after the administration of higher doses of STZ has never been examined in channel catfish. My biggest contribution to this experiment has been to study the expression of the Hyaluronan synthases (HAS2 and HAS3), which are membrane-bound enzymes in mammals, in various catfish cDNA samples before and after injection of STZ. These enzymes are directly related to the production of Hyaluronan (HA) in the blood in response to severe tissue damage.

Channel catfish kept in aquariums inside the FHSU grounds department building. Photo credit: Megan Dougherty, Fort Hays State University

Realities of Research

Conducting research in a laboratory setting is very much how I expected. I had minimal pipetting experience from a biochemistry course I had previously taken, so I knew perfecting my technique should be first priority. This basic skill is so important in ensuring that the data I am collecting are going to be accurate and useful in the final analysis. I found it interesting that the assays we were conducting were extremely sensitive to the surrounding environment and realized the importance of keeping a clean laboratory space. A peer in my lab experienced some setbacks involving contamination in the blank tube of her PCR results. We were able to detect the contamination through a picture taken after gel electrophoresis, and we were then able to try to identify where the contamination could possibly be coming from. We eventually had to take a full day to clean the entire lab bench with ethanol and a bleach/water solution to try to get rid of the problem. There haven’t been any issues since the lab group took that step. My results in this experience so far have been as expected. I haven’t found an expression of HAS2 or HAS3 in any tissue samples collected from catfish before STZ treatment by just using the basic PCR and gel electrophoresis technique. This is not surprising. My mentor has explained that these enzymes would not be expressed in high amounts until after the fish have been injected with STZ because they are related to the repairing of tissue damage. Because low concentrations of HAS should be expressed in some healthy tissues, however, my mentor has just recently taught me how to conduct real-time PCR to visualize the results in a different way. Once STZ treatment is complete, I do expect to be able to visualize HAS2 and HAS3 mRNA expressed at a higher concentration, primarily in the liver.

Life of a Scientist

Overall, my research experience has been a very positive one. I have realized how important working as a team in a laboratory setting is. It is very useful to understand what your peers are experimenting on and be available to help them along the way. This leads to building strong relationships and a plentiful collection of data. I have also learned that it is important to stay flexible throughout experimentation and to understand that getting no results is not necessarily a bad thing. It just means that new options and techniques need to be explored to find exactly what you are looking for. My mentor has been great at keeping me and my peer motivated throughout this experience by answering any questions we have and helping us, whether the issue is not getting results or getting results that are contaminated. The best part about working in a lab is leaving each day feeling accomplished and knowing that I am learning so many new things. Another great aspect of my summer research is that I can feel myself becoming more confident with the procedures I have learned as time goes on. I find myself asking for less help and getting things done correctly in a timelier manner. The worst part about research is going through a lot of small steps and spending time on assays that do not show any results at the end of a long day. I sometimes feel as if time is wasted when this happens, but it is important to remind myself that no results still reveal something about the overall experiment.

Preparing to run gel electrophoresis. Photo credit: Abigail Schmidtberger, Dr. Kobayashi’s research lab, Fort Hays State University


  1. Nevarez E, Ordonez-Castillo N, Spainhour R, Kobayashi Y. Treatment with Streptozotocin (STZ) causes hypoglycemia and alters the stability of reference genes for real-time PCR analysis in the liver of channel catfish [Online]. The Official Journal of the Federation of American Societies for Experimental Biology. [12 July 2017].
  2. Itano N, Sawai T, Yoshida M, Lenas P, Yamada Y, Imagawa M, Shinomura T, Hamaguchi M, Yoshida Y, Ohnuki Y, Miyauchi S, Spicer AP, McDonald JA, Kimata K. Three Isoforms of Mammalian Hyaluronan Synthases Have Distinct Enzymatic Properties [Online]. Journal of Biological Chemistry. [12 July 2017].
Megan Dougherty is an upcoming senior majoring in Biology with an emphasis in Health Professions at Fort Hays State University in Hays, Kansas. She is a 2017 Integrative Organismal System Physiology (IOSP) Fellow working in Dr. Yashiro Kobayashi’s lab at Fort Hays State University in Hays, Kansas. Megan’s fellowship is awarded by the APS and a grant from the National Science Foundation Integrative Organismal Systems (IOS) (Grant #IOS-1238831). After graduation, Megan plans to attend a graduate program in hopes of pursuing a career as a physician assistant or medical technologist.

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