Stability of bombesin in serum, plasma, urine, and culture media

Using a radioimmunoassay, we studied the stability of bombesin added to pooled human serum, plasma, urine, and two culture media (RPMI-1640 and M199). Bombesin was stable in serum for 5 h at 4 °C and 2 h at 21 °C. However, in plasma, about half was no longer detected by 5 h at 4 °C, and this decline was unaffected by added aprotinin. Bombesin was stable in urine for 24 h at 4 °C and for 2 h at 21 °C. When incubated in the culture media at 37 °C for 60 min, no loss was detected. Bombesin-like immunoreactivity was detectable in the serum of 22 mice bearing tumors established from biopsied small-cell lung carcinomas, two of 12 mice bearing tumors established from other malignancies and zero of nine control mice. In contrast, immunoreactivity to this analyte was detected in urine specimens from all mice except for one bearing a non-small-cell tumor. The concentrations detected in serum and urine were uncorrelated.