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On the binding of the bisquaternary ammonium compound paraquat to melanin and cartilage in vivo

1978; Elsevier BV; Volume: 27; Issue: 13 Linguagem: Inglês

10.1016/0006-2952(78)90546-4

1873-2968

Bengt Larsson, Agneta Oskarsson, Hans Tjälve,

Peroxisome Proliferator-Activated Receptors

The bisquaternary ammonium compound paraquat has been shown to accumulate in melanin-containing tissues and in cartilage in vivo. The present study was intended to elucidate if ionic binding is involved in the mechanism for the affinity of paraquat to these tissues in vivo. Ionic binding has previously been shown to be involved in the binding of paraquat to melanin in vitro and in the binding of other bisquaternary ammonium compounds to cartilage in vitro. [14C]paraquat was given to mice. Whole-body tissue sections were taken and incubated in solutions with different cationic composition. The ability of the cations to displace [14C]paraquat from melanin of the eye and intervertebral cartilages was then determined by autoradiography, using densitometric measurements for the quantitations. It was found that the cations in the incubation solutions were able to displace [14C]paraquat from both melanin and cartilage. The [14C]paraquat was more effectively displaced from cartilage than from melanin. In both tissues divalent cations were more effective than K+ and Na+; and H+ was also effective. The results indicate that ionic binding is involved in the binding in vivo of paraquat both to melanin and cartilage. The binding sites may be carboxyl groups present in the subunits in melanin and ester sulphate and carboxyl groups of chondroitin sulphate in cartilage. The stronger binding of paraquat to melanin may depend on extra interactions due to conjunctions of the aromatic rings of the paraquat and the melanin polymer.