Using an antiserum directed at the COOH-terminus of
tachykinins, we have examined postmortem tissue from two cases of metastatic ileal
carcinoid for the presence of
tachykinin-like immunoreactivity. The vast majority of the immunoreactive
tachykinin-like material eluted from a
Sephadex G-50 column as two peaks at positions corresponding to molecular weights of 1300 and 850. The 1300 dalton peak was resolved by reverse-phase-HPLC into two components which by Edman sequencing,
amino acid analysis, and fast atom bombardment (FAB)-mass spectrometry criteria, were identified as
substance P and
substance K. The 850 dalton peak was also resolved on RP-HPLC into two peaks which were resistant to Edman degradation but from
amino acid analysis and FAB-mass spectrometry criteria were identified as pyro-Glu-
substance P 5-11 and oxidized pyro-Glu-
substance P 5-11. In control experiments
substance P 5-11 was converted to pyro-Glu-
substance P 5-11 during the extraction procedure. Both
tumors also contained a minor immunoreactive peak which eluted from a
Sephadex G-50 sizing column at a position corresponding to a molecular weight of 4000 which probably represents
neuropeptide K. These results suggest that
beta-preprotachykinin is preferentially expressed in
carcinoid tumors and that
substance K may also play a role in the
carcinoid syndrome.