Ionophores have limited effects on jejunal glucose absorption and energy metabolism in mice

Abstract

Two experiments, Trial 1 (in vitro) and Trial 2 (in vivo), were conducted to examine the effects of ionophores, monensin, laidlomycin, and laidlomycin propionate on whole-animal O2 consumption, organ weights, jejunal glucose absorption, and O2 utilization, as well as growth, feed and water consumption, and feed efficiency. In Trial 1, 30 male Swiss-Webster mice, 8 wk old, were used to measure the in vitro effects of each of the ionophores at concentrations of 1.62 or 16.2 mM. Six combinations of three ionophores at two concentrations resulted in a total of eight treatments. All eight treatments were exposed to jejunal rings from a single mouse for a total of 30 observations per treatment. Jejunal rings were exposed to each ionophore treatment for 15 min. Laidlomycin propionate (16.2 mM) decreased (P < 0.02) glucose absorption, as estimated by H3-3-O-methyl glucose uptake compared with all other treatments, whereas laidlomycin propionate (1.62 mM) increased (P = 0.032) jejunal DM content compared with 16.2 mM laidlomycin propionate. In Trial 2, 40 5-wk-old mice were allotted into four treatments--control and 16.2 mM each of monensin, laidlomycin, and laidlomycin propionate--for a total of 10 observations per treatment. Ionophores were administered via the drinking water for 14 d. No ionophore treatment had any effect on whole-mouse O2 consumption. Monensin increased (P = 0.004) stomach size and decreased (P = 0.049) the efficiency of BW gain compared with controls. Laidlomycin propionate decreased (P = 0.032) the percentage of whole jejunum oxygen consumption due to oubain-sensitive respiration compared with control. The efficiency of intestinal glucose absorption was not changed due to treatment in either trial. Under the conditions of these studies, monensin, laidlomycin, and laidlomycin propionate had minimal and inconsistent effects on jejunal function and energy utilization in mice. This investigation suggests that changes in the energetic requirements of animals treated with ionophores are not an issue in animal production.

Effect of Genotype on Whole-body and Intestinal Metabolic Response to Monensin in Mice

“…There have been reports that monensin decreased oleic acid absorption in rat enterocytes (Husenet et al, 1990) and intestinal cholesterol uptake from cultured human intestine (Sviridov et al, 1993). Our laboratory failed to find any effects of the ionophore antibiotics, laidlomycin, laidlomycin propionate or monensin on wholebody energy metabolism or jejunal function of Swiss Webster mice (Fan et al, 2003).…”

“…The small intestine was weighed and its unstretched length recorded. The mid-jejunum was removed at its midsection for glucose transport and respiration measurements as well as histological morphometric measurements and biochemical analyses (Fan et al, 2003).…”

“…Either intact jejunal tissue or serosal tissue pieces were placed in incubation chambers fitted with an O 2 electrode containing 4 ml of media 199 and constantly stirred at 37°C to measure O 2 consumption rate. The O 2 consumption rate of intestinal mucosa was estimated using the difference between the O 2 consumption rate of intact jejunal tissue and that of the serosa (Fan et al, 2003). Oxygen consumption rates of jejunal intact tissue and serosal tissue attributable to Na + /K + -ATPase were measured by the differences in O 2 consumption in the presence and absence of ouabain, an inhibitor of Na + /K + -ATPase (Sigma Chemical Co., St. Louis, MO), respectively.…”

“…The ouabain sensitive proportion and the monensin sensitive proportion in jejunal intact tissue respiration were calculated by subtraction of total jejunal tissue respiration from those inhibited by ouabain and monensin, respectively (Fan et al, 2003). Glucose active transport was calculated as the difference between 3OMG accumulation in the media with and without phlorizin (Fan et al, 1996).…”

“…New genetic lines are constantly emerging as a result of selection for enhanced production traits such as growth and body composition. The complex manner in which whole-body and intestinal function may be altered during genetic selection (Croom et al, 1998(Croom et al, , 1999 in animal production systems makes it unlikely that one study using a genotype such as that reported by Fan et al (2003), could reflect possible wholebody and intestinal response to an ionophore antibiotic over a diverse range of genotypes within a species.…”