To extract or not to extract in secretin radioimmunoassay?
The importance of an ethanol extraction procedure in the radioimmunoassay of plasma secretin was investigated. The extraction step led to a higher assay sensitivity of 0.35 fmol/ml, compared to 5.93 fmol/ml using unextracted samples. The rise of plasma secretin after infusion of a low dose of secretin (1 pmol.kg-1.h-1) in 10 healthy humans was only detected after sample extraction. Higher doses (3 and 9 pmol.kg-1.h-1) resulted in increments of plasma IRS (immunoreactive secretin), which could be recorded both with and without sample extraction. After a steak meal 7 of 10 subjects showed a significant increase of plasma secretin assaying extracted plasma samples. The secretin release occurred in spikes. The mean increase of plasma IRS in this group was 0.6 fmol/ml, the mean maximal secretin release above basal was 2.3 fmol/ml. Without sample extraction, plasma secretin was not significantly changed. We conclude that plasma samples should be extracted in order to detect physiological postprandial secretin release.
Fried
M
M
Outpatient Clinic, University Hospital Basel, Switzerland.
Schulthess
C
C
Beglinger
C
C
Müller
B
B
Gyr
K
K
D000818:Animals; D005502:Food; D006801:Humans; D011817:Rabbits; D011863:Radioimmunoassay / Q000379:methods; D012633:Secretin / Q000097:blood*
D012633:Secretin