Dietary manganese suppresses alpha1 adrenergic receptor-mediated vascular contraction

Area of Science:

• Cardiovascular Physiology
• Nutritional Biochemistry
• Vascular Pharmacology

Background:

• Dietary manganese (Mn) is essential for various physiological processes.
• The specific effects of dietary manganese on vascular smooth muscle contractility are not fully understood.

Purpose of the Study:

• To investigate the impact of varying dietary manganese levels on the contractile machinery of rat thoracic aortas.
• To determine how manganese influences vascular smooth muscle cell response to alpha(1) adrenergic receptor stimulation.

Main Methods:

• Weanling male Sprague-Dawley rats were fed manganese-deficient, adequate, or supplemented diets for 15 weeks.
• Aortic rings were contracted with L-phenylephrine (alpha(1) adrenergic agonist) and relaxed with acetylcholine.
• Maximal contraction force (Fmax) and sensitivity (pD2) to L-phenylephrine were measured.

Main Results:

• Manganese-supplemented diet (45-50 ppm) resulted in lower maximal contraction force (Fmax) compared to deficient and adequate groups.
• Manganese deficiency significantly increased vascular sensitivity (pD2) to L-phenylephrine.
• Hepatic manganese content indicated successful dietary manipulation and affected animal growth rates.

Conclusions:

• Dietary manganese levels significantly influence the contractile machinery of vascular smooth muscle.
• High dietary manganese reduces maximal contractile responses to alpha(1) adrenergic agonists.
• Manganese deficiency enhances vascular sensitivity to alpha(1) adrenergic receptor stimulation, impacting signaling pathways.