Circulating tachykinins (substance P, neurokinin A, neuropeptide K) and the carcinoid flush.
Antisera of defined regional specificity have been used to measure the concentration of substance P-like immunoreactivity (SP-LI) and neurokinin A-like immunoreactivity (NKA-LI) during a meal-induced flush in 10 patients with metastatic carcinoid tumours. Although all patients flushed, NKA-LI levels in five patients and SP-LI in six patients were not elevated relative to healthy subjects (NKA-LI, less than 3 pg/ml; SP-LI, less than 10 pg/ml) both in the fasted state and after food. In the patients with elevated basal plasma tachykinin levels, increases in NKA-LI and SP-LI after food were erratic and did not correspond to a defined digestive phase or the occurrence of the flush. Chromatographic analysis of plasma demonstrated the presence of neuropeptide K and neurokinin A, and the detection of COOH-terminal fragments of substance P is consistent with the higher levels of circulating SP-LI measured with a COOH-terminally directed antiserum compared with an NH2-terminally directed antiserum. Subcutaneous injection of the somatostatin analogue SMS 201-995 (50 micrograms) alleviated symptoms of flush in two of three patients but only partially suppressed NKA-LI and SP-LI concentrations. It is concluded that circulating tachykinins cannot be solely responsible for the meal-induced carcinoid flush.
D000328:Adult; D002276:Carcinoid Tumor / Q000097:blood*; D005260:Female; D005502:Food; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D008875:Middle Aged; D015288:Neurokinin A; D009479:Neuropeptides / Q000097:blood*; D015282:Octreotide; D010455:Peptides / Q000097:blood*; D013004:Somatostatin / Q000031:analogs & derivatives / Q000494:pharmacology; D015320:Tachykinins
D036341:Intercellular Signaling Peptides and Proteins; D009479:Neuropeptides; D010455:Peptides; D015320:Tachykinins; C045206:neuropeptide K; C016116:substance P-like peptides; D013004:Somatostatin; D015288:Neurokinin A; D015282:Octreotide