Chronotropic responses in rats implanted with an acrylic orthopaedic cement

Area of Science:

• Pharmacology
• Cardiovascular Physiology
• Toxicology

Background:

• Methyl methacrylate is a monomer used in various applications, including dental prosthetics and bone cement.
• Exposure to methyl methacrylate may have toxicological effects on physiological systems.
• Understanding its impact on cardiovascular function is crucial for assessing health risks.

Purpose of the Study:

• To investigate the effects of methyl methacrylate polymer exposure on cardiac chronotropic and inotropic responses in rats.
• To determine the specific mechanisms underlying any observed alterations in cardiac function.
• To assess the impact on the adenylate cyclase signaling pathway.

Main Methods:

• Isolated rat atria and papillary muscles were used.
• Animals were exposed to a methyl methacrylate polymer pellet for one week.
• Responses to isoproterenol, glucagon, dibutyryl cAMP, and calcium chloride were measured.
• Beta-receptor density and affinity were assessed.

Main Results:

• Right atria from exposed rats showed reduced responsiveness to isoproterenol and glucagon (chronotropic effects).
• Responsiveness to dibutyryl cAMP and calcium chloride remained unchanged.
• Inotropic responses in left atria and papillary muscles were not altered.
• No changes in beta-receptor density or affinity were detected.

Conclusions:

• Methyl methacrylate exposure disrupts the signal transduction pathway for chronotropic stimuli mediated by the adenylate cyclase system.
• The alteration occurs downstream of beta-receptor binding and upstream of cyclic AMP (cAMP) action.
• This suggests a specific interference with intracellular signaling components involved in regulating heart rate.