Zn2+ and Cd2+ increase the cyclic GMP level in PC12 cells by inhibition of the cyclic nucleotide phosphodiesterase.
In the present study, the influence of the heavy metal ions Cd2+ and Zn2+ on cGMP metabolism in the neurosecretory rat pheochromocytoma (PC12) cell line has been investigated. Cadmium and zinc ions showed a concentration-dependent increase of intracellular cGMP levels as determined by radioimmunoassay: a 20-fold increase in cGMP concentration was found after 15 min of incubation with 20 microM Cd2+, and a 7-fold increase in cGMP was found after incubation with 50 microM Zn2+ (control: 6.05+/-2.1 pmol cGMP/mg protein). To obtain further mechanistic informations, the effects of Cd2+ and Zn2+ on intracellular 3',5'-cyclic nucleotide phosphodiesterase have been studied by a high performance liquid chromatography-based phosphodiesterase-assay. The cellular cGMP hydrolysis was found to be inhibited by these ions with an IC(50) value of 6+/-0.7 microM for Cd2+ and 13+/-2.5microM for Zn2+ . Hence, dose-dependent increase in cellular cGMP content is due to an inhibition of cGMP hydrolysis and not due to an increase in cGMP synthesis. Cd2+ and Zn2+ were taken up by PC12 cells as determined by atomic absorption spectroscopy, all measurements were performed in a subtoxic concentration range. Our data illustrate that zinc and cadmium ions are efficient inhibitors of the cGMP-stimulated cyclic nucleotide PDEII in PC12 cells resulting in elevated cellular cGMP concentrations. Therefore, subtoxic doses of these metals may disturb intracellular cGMP/cAMP-signalling pathways leading to an impaired or altered gene expression.
Wätjen
W
W
Department of Biology and Chemistry, University of Bremen, Leobener Str. NW2, Bremen D-28359, Germany.
Benters
J
J
Haase
H
H
Schwede
F
F
Jastorff
B
B
Beyersmann
D
D
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors*; D000818:Animals; D002104:Cadmium / Q000493:pharmacokinetics / Q000494:pharmacology*; D006152:Cyclic GMP / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D016716:PC12 Cells; D051381:Rats; D015032:Zinc / Q000493:pharmacokinetics / Q000494:pharmacology*
D002104:Cadmium; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D006152:Cyclic GMP; D015032:Zinc