Effects of the ionophore antibiotics monensin, monensin-propionate, abierixin and calcimycin on ruminal fermentations in vitro (Rusitec)

International audienc

Effects of the ionophore antibiotics lasalocid and cationomycin on ruminal fermentation in vitro

International audienc

Monensin-induced modifications of ionic gradients on Streptococcus faecalis. A

The study of Na+ (23Na NMR), H+ (31P NMR) and K+ (atomic absorption) movements was performed on Streptococcus faecalis cells, with or without monensin addition. Our approach with energized or de-energized cells allowed the distinction between the ionophore effect and the bacterial carriers response. At high monensin concentration the intrinsic systems of the bacteria were unable to re-establish normal ionic gradients. The high selectivity of transport of the ionophore for Na+ / K+ as measured in model physico-chemical sytems, was not determining “in vivo” as the most important damage caused to the bacteria was a large K+ efflux

Etude « in vitro » de quelques antibiotiques ionophores et de certains de leurs dérivés. II. Caractérisation des propriétés ionophores des composés dans un système modèle, pour les ions Na +

International audienc

Mode of action of calcimycin (A 23187). VI. Complexation of transition and heavy metal divalent cations in methanol

Interaction between calcimycin HA and transition and heavy metal divalent cations M2+ in methanol was studied using potentiometry. Both MA+ and MA2 complexes are formed, except for Pb2+. The corresponding stability constants were obtained; these were high. Formation of further species involving the methanolate anion in the coordination of the metal cation is scarse. The selectivity of calcimycin anion for the various divalent cations is determined by the selectivity of its carboxylate group

In vitro study of the effect of different ionophore antibiotics and of certain derivatives on rumen fermentation and on protein nitrogen degradation

International audienc

Mode of action of calcimycin (A23187)

Formation constants of complexes and basic complexes of calcimycin with lanthanum, gadolinium and europium (III) cations were obtained in methanol using a potentiometric method. E.s.r. spectra of gadolinium for varying concentrations of gadolinium perchlorate, calcimycin and tétrabutylammonium methoxide afforded identification of the various species formed. Results obtained are discussed in terms of equilibria, structures and transport of lanthanide cations by calcimycin