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Abstract: Previously, we have provided evidence from in vitro adsorption assays that specifically developed polymer adsorbents (molecularly imprinted [MIP] and nonimprinted [NIP]) can bind alkaloids. To aid in understanding the physiological significance, here we report on research using ex vivo models. The objective was to investigate the physiological significance of MIP and NIP application using ex vivo myography and to compare the impact of MIP and NIP on the ergot alkaloid bioavailability. Lateral saphenous veins were collected from 17 steers (2 veins/steer) for 4 independent studies: 1) dose response of ergotamine (ETA), 2) validation of adsorbent dose, 3) validation of incubation conditions, and 4) evaluation of MIP and NIP (n = 10, n = 6, n = 6, and n = 12, respectively). Products were also evaluated using in vitro isothermal adsorption (ETA [7.813 x 10-7 M] vs. increasing polymer). For Exp. 1, 2, and 4, 1-way ANOVA (GraphPad Prism) was used to analyze data within a CRD. Means were compared using Tukey's test. Percent contractile response normalized to norepinephrine, fitted with a 3-parameter nonlinear regression model (R2 = 0.95) for ETA concentrations (9.8 x 10-8 to 5.0 x 10-5 M), exhibited a sigmoidal response with a maximum of 86.8 ± 7.3% and log EC50(-log[ETA]) of 6.59 ± 0.26 M. Increasing polymer inclusion using a log2 scale (0.625 to 10 mg), as compared with a log10 scale (0.0001 to 1 mg), improved curve fits. Ergotamine added immediately upon thawing increased (P < 0.05) contractile response compared with addition after 1 h incubation at 39 or 20 °C. Isothermal adsorption showed a maximum adsorption of approximately 96% (7.52 x 10-6 mol/10 mg) for both products, with an affinity coefficient (Kd; mg/10 mL) of 0.51 ± 0.10 (R2 = 0.92) and 0.57 ± 0.19 (R2 = 0.83) for MIP and NIP, respectively. At the maximum isothermal adsorption, a maximal reduction of 11.24 ± 2.25 and 9.30 ± 2.74% in contractile response was obtained for MIP and NIP, respectively. Imprinted polymer had better inhibitory response (IC50 = 0.28 ± 0.19 mg) than NIP (IC50 = 0.83 ± 0.26 mg). Comparing in vitro and ex vivo, the trend between the 2 products remained the same, and MIP had a better adsorption affinity (low Kd) to ETA and caused greater inhibition in contractile response (low IC50). Percent contraction was predicted from the adsorption data using the equations y = 0.98 ± 0.06(x) + 0.15 ± 2.07 (R2 = 0.82, P < 0.01) and y = 0.92 ± 0.05(x) - 1.35 ± 1.74 (R2 = 0.87, P < 0.01) for MIP and NIP, respectively. These studies indicated that synthetic polymers are potentially effective adsorbents toward ergot alkaloids that could mitigate their impact, provided that they could be used in animals. Although earlier studies pointed towards an increased specificity of MIP towards alkaloids adsorption, no differences were observed between products. The ex vivo efficacy of both polymers was accurately predicted from in vitro adsorption data
Template and target information: ergotamine, ETA