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Pharmacodynamics of stannous chelates administered with 99mTc-labeled chelates
Abstract:
The pharmacodynamics of several tin compounds were studied in healthy rabbits, rabbits with myocardial infarcts, and isolated myocardial tissue. The results showed that tin chelates of pyrophosphate, HEDP, DTPA, and glucoheptonate are very unstable in vivo, giving rise to free stannous ions. These ions localize mainly in bone, with the rest being primarily excreted in the urine. They also concentrate more in infarcted than in normal myocardium; there they enter the mitochondria. The supernatant of homogenates contains bound and free fractions, demonstrating a subcellular distribution pattern similar to that of calcium ions. Tin chelates have different pharmacodynamics from the corresponding 99mTc chelates.
Insights
Tin chelates are unstable in vivo, releasing free stannous ions. These ions accumulate in bone and concentrate in damaged heart tissue, differing from technetium-99m chelates.
Area of Science:
- Pharmacology
- Toxicology
- Biochemistry
Background:
- Tin compounds are investigated for potential medical applications.
- Understanding the in vivo behavior of tin chelates is crucial for safety and efficacy.
- Myocardial infarction alters tissue environments, potentially affecting drug distribution.
Purpose of the Study:
- To investigate the pharmacodynamics of various tin chelates in vivo.
- To determine the distribution and excretion of tin ions derived from these chelates.
- To compare the behavior of tin chelates with their corresponding technetium-99m counterparts.
Main Methods:
- Pharmacodynamic studies were conducted in healthy rabbits and rabbits with induced myocardial infarcts.
- Isolated myocardial tissue was used to assess tin ion localization.
- Subcellular distribution patterns were analyzed using tissue homogenates.
Main Results:
- Tin chelates of pyrophosphate, HEDP, DTPA, and glucoheptonate demonstrated in vivo instability, releasing free stannous ions.
- Free stannous ions primarily localized in bone and were excreted via urine.
- A higher concentration of tin ions was observed in infarcted myocardium compared to normal myocardium, with mitochondrial entry noted.
Conclusions:
- The pharmacodynamics of tin chelates are characterized by the release of free stannous ions.
- Stannous ions exhibit specific tissue distribution, with accumulation in bone and infarcted myocardium.
- Tin chelates possess distinct pharmacokinetic profiles compared to their 99mTc analogues.