Kidney Week

Abstract: FR-PO559

A Novel State-of-the-Art Intravital Microscopy Technique to Track Magnesium in Living Kidneys

Session Information

• Fluid, Electrolyte, and Acid-Base Disorders: Basic
  October 25, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Fluid, Electrolytes, and Acid-Base Disorders

• 1101 Fluid, Electrolyte, and Acid-Base Disorders: Basic

Authors

• Leermakers, Pieter A., Radboud Universitair Medisch Centrum, Nijmegen, Netherlands

Pieter A. Leermakers, PhD

• Gyarmati, Georgina, University of Southern California, Los Angeles, California, United States

Georgina Gyarmati, MD, MPH

• Peti-Peterdi, Janos, University of Southern California, Los Angeles, California, United States

Janos Peti-Peterdi, MD, PhD

• Shchepetkina, Veronika, New York University, New York, New York, United States

Veronika Shchepetkina

• Buccella, Daniela, New York University, New York, New York, United States

Daniela Buccella, PhD

• Hoenderop, Joost, Radboud Universitair Medisch Centrum, Nijmegen, Netherlands

Joost Hoenderop, PhD

• De Baaij, Jeroen H.F., Radboud Universitair Medisch Centrum, Nijmegen, Netherlands

Jeroen H.F. De Baaij, PhD

Group or Team Name

• Dept of Medical BioSciences.

Background

Magnesium is an essential mineral for human physiology. Therefore, the serum magnesium concentration is tightly controlled by the kidney. It is currently not possible to measure real-time renal magnesium reabsorption in living organisms. To study the regulation of magnesium reabsorption in the kidney, we aim to perform multi-photon microscopy using a novel ratio-metric magnesium-reporter (MagZet1).

Methods

Mice were anesthetized, received a cannula, and were surgically prepared for kidney imaging. Subsequently, the superficial kidney cortex was continuously imaged with multiphoton microscopy for ratio-metric emission of magnesium-bound and magnesium-free MagZet1, and Albumin-AF594 as a contrast agent. During imaging, injections of Albumin-AF594 and MagZet1 were followed by bolus injections of MgSO_4, CaGluconate, or saline.

Results

in vitro, MagZet1 ratio-metric emission can be used to discriminate <0.2mM changes in [Mg²⁺] in plasma filtrate. In vivo, i.v. injection of MagZet1 results in free renal filtration, and MagZet1 can be detected in plasma and tubular segments in the kidney of live animals. The maximal imaging depth of MagZet1 is less than 100 µm, so only superficial proximal and distal tubules can be imaged with this technique. Injection of MgSO₄ results in an increased MagZet1 fluorescence emission ratio in all visible tubular segments, while injection of saline or CaGluconate did not change the MagZet1 fluorescence emission ratio.

Conclusion

MagZet1 is a magnesium dye that is discriminative of small changes in [Mg²⁺] in physiological conditions. MagZet1 can be detected in live animals in vivo using multi-photon microscopy for at least two hours after injection. In future experiments, we aim to screen the effects of genetic models and candidate drugs on renal magnesium reabsorption.

Funding

• Government Support – Non-U.S.