The present study was designed to investigate the effects of various cadmium concentrations on porcine growth hormone (GH) secretion in serum and cultured pituitary cells and to explore the possible mechanisms of cadmium toxicity. In feeding trial, 192 barrows (Duroc x Landrace x Yorkshire), with similar initial body weights, were randomly divided into four different treatment groups with three replicates for each treatment. The diets were supplemented for 83 days with 0, 0.5, 5.0, and 10.0 mg/kg cadmium (as CdCl2). For the cell culture trial, dispersed pituitary cells were incubated with graded doses of cadmium (0, 5, 10, 15, or 20 microM) for 24 h. Pigs treated with 10 mg/kg cadmium had significantly decreased serum GH content. 3-(4,5-dimethyl-2-yl)-2,5-diphenyl tetrazolium bromide assay showed that Cd toxicity was dose-dependent. Cell viability was reduced to 50% at 15 microM concentration. Administration of cadmium significantly reduced GH secretion, whereas cellular NO content and inducible nitric oxide synthase activity increased to a certain extent. These findings suggest that the decrease of GH might be related to NO production and to a change of NO signal pathway caused by cadmium.