Document Type


Degree Name

Master of Science (MSc)



Program Name/Specialization

Integrative Biology


Faculty of Science

First Advisor

Wilson, Jonathan M

Advisor Role

Supervised lab work, assisted in project development, reviewed and edited thesis


It is well known that stomach acid secretion by oxynticopeptic cells of the gastric mucosa is accomplished by the H+/ K+-ATPase (HKA), which is comprised of the HKα1 (gene: atp4a) and HKβ (gene: atp4b) subunits. However, the role of the HKA in extra-gastric organs such as the gill and kidney is less clear especially in fishes. This pump may contribute to active ion and/or acid-base regulation either through direct ion transport or through secondary transport proteins against unfavorable concentration gradients via the energy derived from ATP hydrolysis. In the present work I have demonstrated uptake of the K+ surrogate flux marker rubidium (Rb+) in vivo in O. niloticus; however, this uptake was not inhibited with omeprazole, a potent inhibitor of the gastric HKA. This contrasts with gill and kidney ex vivo preparations where tissue Rb+ uptake was significantly inhibited by omeprazole and SCH28080, another gastric HKA inhibitor. To determine the cellular localization site of this pump in both gills and kidney I used immunohistochemical techniques using custom made antibodies specific for Atp4a and Atp4b. Antibodies against both subunits showed the same apical ionocyte distribution pattern in gill and collecting tubules in kidney. Taken together these results indicate for the first time K+ (Rb+) uptake in O. niloticus and that the HKA can be implicated by the ex vivo uptake inhibition by omeprazole and SCH28080, verifying a role for HKA in K+ absorption in the gill’s ionocytes and collecting tubule segment of the kidney.

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