Samples of connective tissue obtained from the hoof of six laminitic and eight non-laminitic adult horses were analysed zymographically to investigate whether connective tissue matrix metalloproteinases are activated or induced during laminitis. The activity or matrix metalloproteinases was substantially greater in the tissues from the laminitic horses than in the tissues from the non-laminitic horses. A comparison of the collagenolytic activity in the laminitic and control tissues showed that collagenolytic activities corresponding to the 92 kDa (P < 0.001), 72 kDa (P < 0.01) and 66 kDa (P < 0.01) bands were induced in the laminitic tissues.

Background: While there is evidence of laminar leukocyte infiltration in black walnut extract (BWE)-induced laminitis, there is no such evidence for carbohydrate overload (CHO) laminitis.Objective: To assess presence of leukocytes and signs of epidermal stress/injury in the laminar tissue from horses with CHO-induced laminitis.Animals: Twenty-four adult horses. Methods: Immunohistochemistry for myeloid cell markers calprotectin (CP) and monocyte-specific marker (CD163) was performed on laminar sections obtained from 2 groups of horses in the CHO model: the developmental time point (DTP) group (n 5 6) and the onset of lameness (LAM) group (n 5 6), and a control (CON) group (n 5 8).Results: DTP was characterized by an increase in CP 1 leukocytes (7.8-fold increase versus CON, P o .001), and LAM time point was characterized by a more marked increase in laminar CP 1 (108.5-fold, P o .001) and mild increase in CD163

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