Korean J Nucl Med.  2000 Aug;34(4):303-311.

Effects of Pinacidil, a Potassium-Channel Opener, on Biodistribution of Thallium-201 in Tumor-Bearing Mice

• Lee JT
• Chun KA
• Lee SW
• Kang DY
• Ahn BC
• Jun SH
• Lee KB
• Ha JH

Abstract

PURPOSE: Thallium behaves similarly to potassium in vivo. Potassium channel opener (K-opener) opens ATP-sensitive K+/-channel located at cell membrane, resulting in potassium efflux from cytosol. We have previously reported that K-opener can alter biokinetics of Tl-201 in cultured cells and in vivo. Malignant tumor cells have high Na-K ATPase activity due to increased metabolic activities and dedifferentiation, and differential delineation of malignant tumor can be possible with Tl-201 imaging. K-opener may affect tumoral uptake of Tl-201 in vivo. To investigate the effects of pinacidil (one of the potent K-openers) on the localization of the tumor with Tl-201 chloride, we evaluated the changes in biodistribution of Tl-201 with pinacidil treatment in tumor-bearing mice. MATERAL AND METHODS: Balb/c mice received subcutaneous implantation of murine breast cancer cells in the thigh and were used for biodistribution study 3 weeks later. 100 microgram of pinacidil dissolved in 200 microliter DMSO/PBS solution was injected intravenously via tail vein at 10 min after 185 KBq (5 microcurie) Tl-201 injection. Percentage organ uptake and whole body retention ratio of Tl-201 were measured at various periods after injection, and values were compared between control and pinacidil-treated mice.
RESULTS
Pinacidil treatment resulted in mild decrease in blood levels of Tl-201, but renal uptakes were markedly decreased at 30-min, 1- and 2-hour, compared to control group. Hepatic, intestinal and muscular uptake were not different. Absolute percentage uptake and tumor to blood ratios of Tl-201 were lower in pinacidil treated mice than in the control group at all time points measured. Whole body retention ratio of Tl-201 was lower in pinacidil treated mice (58+/-4%), than in the control group (67+/-3%) at 24 hours after with injection of 100 microgram pinacidil.
CONCLUSION
K-opener did not enhance, but rather decreased absolute tumoral uptake and tumor-to-blood ratios of Tl-201. Decreased whole body retention ratio and renal uptake were observed with pinacidil treatment in tumor-bearing mice.

Keyword

Tl-201; Tumor imaging; Potassium-channel opener

MeSH Terms

Adenosine Triphosphatases
Animals
Breast Neoplasms
Cell Membrane
Cells, Cultured
Cytosol
Mice*
Pinacidil*
Potassium
Potassium Channels
Thallium
Thigh
Veins
Adenosine Triphosphatases
Pinacidil
Potassium
Potassium Channels
Thallium