Cytoplasmic pH and free Mg2+ in lymphocytes

Area of Science:

• Cellular Physiology
• Biochemistry
• Immunology

Background:

• Cytoplasmic pH (pHi) and free magnesium concentration ([Mg2+]i) are critical for lymphocyte function.
• Understanding their regulation is essential for studying cellular responses, including mitogenesis.

Purpose of the Study:

• To measure pHi and [Mg2+]i in pig and mouse lymphocytes.
• To investigate the effects of bicarbonate, CO2, and concanavalin A (Con A) on these parameters.

Main Methods:

• pHi was measured using digitonin null-point, freeze-thawed pellet pH, 31P NMR spectroscopy, and a fluorescent pH indicator.
• [Mg2+]i was assessed via external Mg2+ null-point, Mg-sensitive electrode, and 31P NMR spectroscopy.
• Lymphocytes were stimulated with physiological levels of HCO3-/CO2 and mitogenic concentrations of Con A.

Main Results:

• Resting pHi was approximately 7.0, with transient acidification upon HCO3-/CO2 addition.
• Con A did not affect pHi or [Mg2+]i within the first hour of stimulation.
• Multiple methods yielded consistent estimates for pHi and [Mg2+]i, with [Mg2+]i estimated to be greater than 0.5 mM.

Conclusions:

• Lymphocyte pHi is tightly regulated around 7.0 under basal conditions.
• Early mitogenic stimulation by Con A does not induce significant changes in pHi or free [Mg2+]i.
• The employed methods provide reliable measurements of intracellular pHi and [Mg2+]i in lymphocytes.