The inhibitory effect of insulin on IGFBP-1 secretion by H4-II-E cells is attenuated in the presence of ghrelin. Confluent cells were exposed to increasing concentrations of ghrelin in the absence (open circles) and presence (closed circles) of insulin, for a 5 h incubation period under serum-free conditions. IGFBP-1 concentrations, measured by specific immunoassay, pooled from three experiments each containing 3-4 replicates per condition, are expressed as a percentage of the secretion by control wells. * (effect of insulin at a given concentration of ghrelin); ^† (effect of ghrelin in the presence of insulin).