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The distribution of Mn2+ in rabbit eyes after topical administration for manganese-enhanced MRI
Shenzhi Liang1, Miao Liang2, Yu Zhu1
1Department of Ophthalmology, First Affiliated Hospital of Zhengzhou University Zhengzhou, China.
Purpose:
To analyze the distribution of Mn(2+) in rabbit eyes after topical administration of Mncl2 for manganese-enhanced MRI.
Methods:
Forty-eight Chinese white rabbits were divided into three groups. In group 1 (n = 4), the baseline concentration of Mn(2+) in aqueous, vitreous and serum samples were analyzed. In group 2 and 3, the rabbits received one topical instillation (20 μL) of Mncl2 (1 mol • L(-1)). In group 2 (n = 40), aqueous, vitreous and serum samples were collected and analyzed at predetermined time points (0.5, 1, 2, 4, 6, 12, 24, 48, 72 and 168 hours postdose). Assays were performed using inductively coupled plasma-mass spectrometer (ICP-MS). In group 3 (n = 4), after topical administration of Mncl2, dynamic manganese-enhanced MRI (MEMRI) was performed at predetermined time points. The signal-to-noise ratio (SNR) was calculated to evaluate the enhancements of eyes.
Results:
After topical administration, the maximum concentrations of Mn(2+) in the aqueous and vitreous samples were 11.1641 ± 0.7202 (2 hours) and 1.5622 ± 0.1567 (12 hours). In group 3, the maximum enhancement of aqueous humor (SNR = 108.81 ± 10.65) appeared at 2 hours postdose, whereas, no significant changes were detected in vitreous.
Conclusion:
Mn(2+) could distribute into aqueous humor rapidly after topical administration of Mncl2, whereas, the concentration of Mn(2+) in vitreous body fluctuated in a narrow range over the course. The uptake of Mn(2+) in retina may involve several different pathways.
Insights
Manganese (Mn2+) rapidly distributes into the aqueous humor after topical eye drops, but vitreous humor concentrations remain low. Manganese-enhanced MRI (MEMRI) shows significant aqueous humor enhancement, suggesting potential for ocular imaging.
Area of Science:
- Ophthalmology
- Medical Imaging
- Pharmacokinetics
Background:
- Manganese-enhanced MRI (MEMRI) is an emerging technique for visualizing biological structures.
- Understanding the distribution kinetics of manganese (Mn2+) after topical ocular administration is crucial for optimizing MEMRI protocols.
Purpose of the Study:
- To investigate the distribution and concentration of Mn2+ in rabbit ocular tissues following topical instillation of manganese chloride (MnCl2).
- To evaluate the utility of MEMRI for assessing Mn2+ distribution in the eye.
Main Methods:
- Forty-eight rabbits received topical MnCl2. Aqueous, vitreous, and serum samples were analyzed using inductively coupled plasma-mass spectrometry (ICP-MS) at various time points.
- Dynamic MEMRI was performed, and signal-to-noise ratio (SNR) was calculated to quantify ocular enhancement.
Main Results:
- Peak Mn2+ concentration in aqueous humor was observed at 2 hours (11.16 ± 0.72 μmol/L), while peak vitreous concentration was lower and delayed (1.56 ± 0.16 μmol/L at 12 hours).
- MEMRI demonstrated maximum aqueous humor enhancement (SNR = 108.81 ± 10.65) at 2 hours post-instillation.
- No significant Mn2+ enhancement was detected in the vitreous humor via MEMRI.
Conclusions:
- Topical MnCl2 leads to rapid Mn2+ distribution into the anterior chamber (aqueous humor) of the eye.
- Vitreous humor shows limited and fluctuating Mn2+ concentrations, suggesting restricted penetration or clearance.
- The differential distribution highlights the potential of MEMRI for targeted imaging of anterior ocular structures.
