Hederagenin and medicagenic acid effects on the contractility of bovine isolated abomasum specimens

The diet of ruminants includes several plants rich in triterpenoid saponins, predominantly alfalfa and clovers. Due to numerous pharmacological properties of saponins [1], plants rich in those secondary metabolites are used as phytogenic feed additives in cows [2]. On the other hand, there is only very limited data on saponins' impact on gastrointestinal motility in ruminants. Therefore, the aim of the study was to verify the effect of hederagenin and medicagenic acid on bovine abomasal contractility.

The abomasal tissues were collected from adult cows that underwent routine slaughtering. Saponins were tested on acetylcholine-precontracted strips containing either circular or longitudinal smooth muscles.

The obtained results indicate that both tested saponins are potent contractile agents. Hederagenin used in a concentration of 0.01µM or higher enhanced significantly and dose-dependently the force of acetylcholine-induced contraction. The strongest contraction was measured in circular muscle preparations, if hederagenin was used in a dose of 100µM, in which case it amounted to 184.11 ± 15.50% of acetylcholine-evoked reaction. In case of medicagenic acid a significant increase of the abomasum contractility was noticed even if saponin was used in the lowest tested dose (0.001µM), in which case it amounted to 142.35 ± 4.92% of acetylcholine-induced contraction. The increase of medicagenic acid concentration resulted in further enhancement of abomasum contraction force but there was no clear dose-effect dependency.

Taking into account rather low bioavailability of saponins in cows, it is noteworthy that both tested compounds increased significantly abomasum contractility while applied in very low doses. The contractile character and reversibility of the reactions induced by hederagenin and medicagenic acid allow to presume that their effects do not result from smooth muscle cells damage but rather from enhanced cell permeability and alerted ion flow.

Acknowledgements: The study was supported by a research grant from the National Science Centre Poland No. UMO- 2012/05/D/NZ9/01610.

Keywords: Triterpenoid saponins, abomasum, smooth muscle, contractility.

References:

[1] Francis G, Kerem Z, Makkar HPS, Becker K. The biological action of saponins in animal systems: a review. Br J Nutr 2002; 88: 587 – 605

[2] Cheeke PR. Actual and potential applications of Yucca schidigera and Quillaja saponaria saponins in human and animal nutrition. In: Oleszek W, Marston A, editors. Saponins in food, feedstuffs and medicinal plants. Dordrecht: Kluwer Academic Publishers; 1999: 241 – 254