Ghrelin is an acylated peptide that stimulates the secretion of growth hormone. Ghrelin is isolated primarily from the stomach as an endogenous stimulator for growth hormone secretagogue receptor. This highly conserved peptide is mostly produced by cells in the oxyntic glands of the stomach, and it is released into the bloodstream. It has recently been speculated that ghrelin regulates food intake and energy balance. Various mechanisms have been reported to regular the secretion of ghrelin. However, the effects of stress or environmental compounds on ghrelin secretion are still unclear. Nonylphenol (NP) is a ubiquitous compounds degraded from nonylphenol polyethoxylate, that is widely used non-ionic surfactant in detergents, paints, herbicides, and many other synthetic products. Nonylphenol is also regarded as an environmental hormone because it interferes with the sexual functions of individuals. To investigate the effects of NP on ghrelin secretion, we produced antiserum YJC 13-31 against the rat ghrelin in the rabbit and a double antibody radioimmunoassay (RIA) for ghrelin has been developed. The RIA was also available to detect the ghrelin in tissue extract with good parallelism to the standard curve of rat ghrelin. In the present study, oral gavages of NP 50 mg/kg, 100 mg/kg, 200 mg/kg, or vehicle of the same amount were performed every morning in young rats from 19 to 25 days after birth. The young rats were decapitated at 8:30 AM on the day 26 after birth. Trunk blood samples and sera were obtained after RIAs of ghrelin and corticosterone. Gavage of saline was sufficient to raise serum ghrelin from 2.6 ± 0.2 ng/ml to 6.7 ± 0.7 ng/ml (P< 0.01). Gavage with NP suppressed the elevation of serum ghrelin levels in a dose-dependent manner. Besides, gavages of saline elevated the serum levels of corticosterone from 108.8 ± 13.5 ng/ml to 188.7 ± 23.5 ng/ml (P< 0.01) but the elevation effects of corticosterone from gavages were overcame by NP in low dose (50 mg/kg). These results suggested that ingestion of NP is harmful to young animals during growing and environmental adaptation.(poster)