Aims: 

We have previously studied the effect of Mn (MnCl₂ 3 mg/kg, 7 days), in rats, healthy and with alloxan-induced diabetes and shown there is no correlation between Mn influences upon blood glucose and total antioxidant status. Then we found among others that endothelium-dependent relaxation (EDR) induced by carbachol (10^-5 M) could be affected by Mn.

Methods: 

We have repeated the experiments in healthy rats using a higher Mn dose (MnCl₂ 10 mg/kg, 7 days). The animals were sacrificed to study the contractile activity in ring fragments from the aorta and small mesenteric arteries, in isometric conditions.

Results: 

We observed the reduction down to disappearance of EDR in both vessel types, with no changes in the contracting effects of K 40 mM and phenylephrine 10^-5 M, or in the relaxing effects of nitroglycerine 10^-6 M (upon both precontractions) and methoxy-verapamil (D600) 10^-5 M (in K-contracted rings). In resistance arteries the EDHF component of EDR (in presence of 0.01 mM L-NAME and 0.01 mM indomethacin) was increased, partially compensating the reduction by Mn of nitric oxide dependent relaxation.

Conclusion: 

We show for the first time the appearance of toxic Mn effects upon endothelium at doses way bellow those recognized as toxic at the hepatic and neural level.

*CNCSIS grant A/1222 **CNCSIS grant interdisciplinary platform/68