Immunohistochemical detection of gastrin and motilin peptides, their receptors, VIP receptors and caspase activity from the abomasal wall of cattle

摘要

ObjectiveThe aim of this study was to examine the possible effects of gastrin, motilin peptides, their receptors and vasoactive intestinal polypeptide (VIP) receptors on the occurrence of abomasal displacement (AD). A decreased amount of stimulating factors (motilin, motilin receptors) accompanied by an increased amount of inhibiting factors (gastrin, gastrin receptors, VIP receptors) in the abomasal wall could be a cause of the hypo- or atony of the abomasum prior to the abomasal displacement. The caspase-3 activity of the abomasal wall was also examined as apoptosis marker in order to investigate the degree of impairment of the abomasal wall between healthy cows and cows with AD. Material and methodsBiopsies of the corpus abomasi and antrum pylori were available from 20 slaughtered German Holstein cows and from 20 German Fleckvieh cows. Furthermore, material from 20 other German Holstein cows with abomasal displacement as well as biopsies from another three cows of this breed were available. In the latter, an abomasal impaction was experimentally induced by placing a variable gastric band. The paraffin embedded biopsy samples were cut 6µm thick with a microtome for the immunohistochemical investigations. The positive signals were quantified by measuring the stained areas using semiautomatic software program AnalySIS® (Olympus). In this study gastrin and motilin peptides, their receptors, VIP receptors and caspase-3 were stained immunohistochemically (ABC-/AEC-technique).ResultsGastrin was detected only in the tunica mucosa of the antrum. No significant breed difference was found between German Holstein (GH) and German Fleckvieh (GFV) regarding the immunoreactive (IR) area of this gastrointestinal peptide (GFV: 1174 ± 655 µm², GH: 1105 ± 930 µm²). The comparison between GH with abomasal displacement (AD) and without AD, GH cows with AD revealed a larger IR gastrin area (GH with AD: 1277 + 863 µm²). However, this difference was not significant. Gastrin receptors (CCKBR) were detected neither in GH nor in GFV cows in the tunica muscularis of the abomasal wall. Motilin also could not be detected in any layer of the abomasal wall of both breeds contrary to the motilin receptors. In both localizations of the abomasal wall of GFV cows, the IR area for these receptors tended to be larger than in GH cows without AD (antrum: 206 ± 57 µm² vs. 179 ± 53 µm²; corpus: 172 ± 69 vs. 152 ± 52 µm²). No significant differences were found in this regard (p = 0.11). The intra-breed comparison observed significant larger motilin receptor IR areas in GH cows without AD compared to GH cows with AD in both localizations (antrum: 125 ± 55 µm²; corpus: 124 ± 43 µm²; p = 0.003). In GH cows with experimentally induced abomasal impaction, a decrease of the IR area of motilin receptors was detected after placing the gastric band for 72 hours (antrum, 1st OP: 95 ± 46 µm², 2nd OP: 47 ± 8 µm²; corpus, 1st OP: 101 ± 19 µm²; 2nd OP: 80 ± 28 µm²), however this decrease was not significant (p = 0.27). Regarding the number of VPAC1 receptor in the abomasal wall, no inter-breed difference could be detected (antrum: GFV 19 ± 10, GH 18 ± 6; corpus: GFV 19 ± 10, GH 18 ± 8). However, GH cows with AD have a significant higher number of these receptors compared to the healthy cows of this breed (GH with AD antrum: 24 ± 11, corpus: 26 ± 11; p = 0.005). It is also observed that, experimental induction of an abomasal impaction has also increased the number of VPAC1 receptors (antrum, 1st OP: 13 ± 5, 2nd OP: 15 ± 4; corpus, 1st OP: 16 ± 6, 2nd OP: 20 ± 10), however this difference was not significant. Caspase activity, as a criterion for the impairment of the abomasal wall, was significantly higher in GH cows with abomasal displacement compared to healthy GH cows (GH cows with AD antrum: 26 ± 11%, corpus: 29 ± 9%, GH cows without AD antrum: 17 ± 6%, corpus: 21 ± 7%, p = 0.002). The same tendency was also observed in GH cows with experimentally induced AD, however this difference was not significant (p = 0.12). Also no significant difference was detected in the ratio of apoptotic cells between both breeds. ConclusionsThe motilin receptor seems to have an important role in the abomasal motility. Motilin receptors are detected in the tunica muscularis of abomasal wall of all subjects. The tendency that GFV cows have higher amounts of motilin receptors in their abomasal wall, might explain why the cows of this breed are less susceptible to AD. The reduced amounts of motilin receptors in the GH cows with AD and experimentally induced abomasal impaction, in comparison to the healthy GH cows, indicates that AD could cause mechanical destruction of these receptors due to the mechanical stretching or hypoxia of the abomasal wall, to which the increase of the caspase activity could provide evidence.Gastrin seems not to be involved in the occurrence of AD. The absence of the gastrin receptors in the abomasal wall found in this study supports this finding.A lower amount of motilin receptors and a higher amount of VPAC1 receptors in GH cows with AD, compared to healthy GH cows, could be an explanation for the occurrence of AD in these cows. However, according to the results gathered from the subjects with artificially induced abomasal impaction indicates that these changes were likely a consequence of AD itself, rather than being a cause of it.