Heterogeneity of Immunoreactive Motilin

Abstract

Motilin-like immunoreactivities were examined in extracts of duodena of pig, human, dog, rat, cat, rabbit and guinea pig with a combination of radioimmunoassays using three different antisera possessing distinct region-specificities. Antisera GP-1103 and R-1104 were rather C-terminal specific, but the immunological feature of GP-1103 was different from that of R-1104. In the case of antiserum GP-1103, the Glu residue in position 15 in the motilin molecule participated in antigen-antibody interaction, but not in the case of R-1104. Antiserum MBR-02 was N-terminal specific, with of the three assay systems, only a single major peak was detected in the elution profile from BioGel P-10 column of motilin-like immunoreactivity in the porcine duodenal extract, of which the elution volume corresponded to that for synthetic porcine motilin. On the other hand, the gel filtration profiles of the human and canine duodenal extracts consisted of two or three peaks of the immunoreactivity. The major peak emerged in the elution volume identical with that for synthetic porcine motilin and the other two peaks were eluted earlier. The peak which was eluted in the volume corresponding to that for BSA marker was detectable only by the assay system with N-terminal specific antiserum MBR-02. The immunoreactivity of the major peak component in the human, canine or rat extract was found to be lower than that in the porcine extract. The present data may indicate the existence of heterogeneity of motilin-like immunoreactivity and species variation of the structure of the immunoreactive motilin.

Radioimmunoassay with Heterologous Antibody(Hetero-Antibody RIA): Utilization of Highly Cross-Reactive Antibody Present in Polyclonal Antiserum.

“…3A). This might be in accordance with the observations by Yanaihara and his coworkers [9,10], who reported that the assay values for motilin depend on antisera with different specificity to epitopes in the motilin molecule.…”

Structure and Expression of the Human Motilin Gene

“…Since the 22-amino-acid peptide (in the human and presumably other species) is encoded on two exons, motilin may in fact comprise two functional domains. Furthermore, the structure of the human motilin gene presented here may represent the basis for the interspecies heterogeneity in the motilin structure which has been observed or inferred by others (Shin et al, 1980). Thus, it is interesting to note that although there is complete amino acid identity between human and porcine motilin, 5 of 22 amino acids are different in canine motilin.…”

Comparative Assessment of Secretin and Motilin Responses to Graded Duodenal Acidification in Anaesthetised Pigs

“…As compared to secretin, motilin required more stringent acidification of the mucosa to be released: the pH thresh old ranged from 1.0 to 1.9. This difference was not likely to reflect defective recognition of motilin-like components because this pep tide was measured with an assay based on the porcine peptide thus alleviating the potential problem of molecular heterogeneity as met with canine or human motilin [21,22], In addition, the immunoreactive substances de tected in plasma by the secretin and motilin assays were essentially similar to the stan dard preparations at gel chromatography.…”