An ecto-ATPase of thyroidal cell membrane

Area of Science:

• Biochemistry
• Cell Biology
• Endocrinology

Background:

• Thyroid cells play a crucial role in hormone regulation.
• Understanding cell surface enzyme activity is vital for comprehending cellular functions.

Purpose of the Study:

• To investigate the presence and localization of adenosine triphosphatase (ATPase) activity in isolated hog thyroid cells.
• To characterize the hydrolysis of adenosine triphosphate (ATP) by these cells.

Main Methods:

• Isolation of viable hog thyroid cells using dispase.
• Incubation of cell suspensions with ATP and various cations (Mg, Na, K).
• Analysis of ATP hydrolysis products (ADP, AMP, adenosine) using homogenates and intact cells.

Main Results:

• Isolated hog thyroid cells maintained high viability.
• External ATP was hydrolyzed by intact cells, primarily dependent on Mg ions.
• Disruption of cells increased ATP hydrolysis, particularly with Na and K, but Mg-dependent hydrolysis remained unchanged.
• Adenosine diphosphate (ADP), adenosine monophosphate (AMP), and adenosine were identified as hydrolysis products.

Conclusions:

• Hog thyroid cells possess Mg-dependent ecto-ATPase activity on their plasma membrane surface.
• The enzyme system hydrolyzes extracellular ATP sequentially to ADP, AMP, and finally adenosine.
• This ectoenzyme activity may play a role in regulating extracellular nucleotide levels.