Adenosine triphosphate--dependent calcium uptake by rat submaxillary gland microsomes

Area of Science:

• Biochemistry
• Cell Biology
• Physiology

Background:

• Microsomes are membrane-bound vesicles derived from cellular endomembranes.
• Calcium ions play critical roles in various cellular processes, including muscle contraction and signal transduction.
• Submaxillary glands are exocrine glands involved in saliva production.

Purpose of the Study:

• To investigate the mechanism of calcium uptake by rat submaxillary gland microsomes.
• To determine the role of adenosine triphosphate (ATP) in this calcium transport process.
• To compare calcium uptake in salivary gland microsomes with that in muscle tissues.

Main Methods:

• Isolation of microsomes from rat submaxillary glands.
• Measurement of calcium uptake in vitro under various conditions.
• Assay of ATP-dependent calcium transport in the presence of cofactors like magnesium and oxalate.

Main Results:

• Rat submaxillary gland microsomes exhibit calcium uptake from the surrounding media.
• Adenosine triphosphate (ATP) significantly enhances calcium uptake, an effect dependent on temperature (not observed at 0°C) and magnesium ions.
• Oxalate and inorganic phosphate further potentiate ATP-dependent calcium uptake, with oxalate showing a greater effect.
• The total calcium content in microsomes is comparable to that reported for skeletal and cardiac muscles, although the uptake rate is slower in salivary gland microsomes.

Conclusions:

• The study demonstrates an ATP-dependent calcium uptake mechanism in rat submaxillary gland microsomes.
• This process is likely mediated by a calcium pump requiring ATP, magnesium, and potentially influenced by oxalate and phosphate.
• The findings suggest that ATP-dependent calcium sequestration may contribute to the regulation of intracellular free calcium levels, facilitating the return of secretory cells to a resting state.