Flavonoids present in ruminant diet affect the contractility of bovine isolated abomasum specimens

Ruminants are constantly exposed to flavonoids present in feed but it is not clear if those phytochemicals have the potential to affect the activity of gut smooth muscle. Therefore, the aim of the study was to verify the effect of three flavonoids on bovine isolated abomasum smooth muscle.

The study was conducted on abomasum smooth muscle collected from healthy dairy cows that underwent routine slaughter. The effect of apigenin, luteolin and quercetin (0.001 – 100 µM) applied in a non-cumulative manner on acetylcholine (ACH)-precontracted abomasum specimens was tested.

The results obtained in studies aimed at testing dose-effect dependence revealed that: (i) apigenin caused dose-dependent myorelaxation; (ii) luteolin acted as a contractile agent, if used in low concentrations and showed a tendency to increase the force of ACH-evoked reaction, if applied at higher doses; (iii) quercetin used in low concentrations enhanced the response to acetylcholine but if it was used in high doses the flavonoid caused clear myorelaxation.

Fig. 1: The effect of apigenin, luteolin and quercetin on ACH-induced contraction of bovine isolated abomasum circular smooth muscle strips.
The results are expressed as % of the contraction caused by acetylcholine applied in the reference dose of 10 µM.
The results are expressed as mean of 5 – 6 independent experiments (± SD). *p ≤0.05 vs. ACh (10 µM) followed by DMSO (0.5%) application.

Interestingly, if flavonoids were used directly in high concentrations the effects were comparable with those evoked by the same phytochemical but applied in the lowest dose. It suggests a non-specific, dose-independent mechanism of action and the possibility that smooth muscle might get used to flavonoids impact and do not respond correctly to a gradual increase of the applied doses in one experiment. Besides, the multiple application of the same flavonoid in the lowest dose revealed that after several treatments the evoked reactions are different from the first one.

Luteolin and quercetin in concentration up to 0.1 µM seem to be potent myocontractile agents. They show the potential to be used as a diet supplement in dairy cattle. Additional to many beneficial effects on animal health, the use of luteolin- and quercetin-rich feed might be used as a method to reduce the likelihood of abomasum dysmotility.