Growth blocking peptide (GBP) is one of the growth regulators in lepidopteran insects. Using RT-PCR, we detected GBP expression in two insect cell lines from Mamestra brassicae, SES-MaBr-4 from the fat body and SES-MaBr-93 from hemocytes. The sizes of the RT-PCR products agreed with the sizes calculated from the GBP cDNA sequence. These findings suggest that GBP is a candidate for an essential growth factor in these insect cell lines.
