Baseline Lung Function and Inflammatory Indices in Guinea Pigs: Effects of Growth, Repeated Lavage, and Orotracheal Intubation

Abstract

We examined the relationships between baseline lung function, weight, and indices of inflammation in bronchoalveolar lavage (BAL) liquid in unsensitized, anesthetized guinea pigs (GPs) and evaluated a model for performing orotracheal intubation and BAL without having to sacrifice the animal. Thirty-six GPs were anesthetized and orotracheally intubated. Lung resistance (R₁₎ and elastance (E₁) were measured. BAL was then performed with sterile saline, and the animal permitted to cover. White blood cells and differentials, total protein (TP), histamine, prostaglandins (PGs) D₂ F_2a E₂ leukotrienes (LTs) B₄, and C₄/D₄/E₄ were measured in the BAL liquid as indices of inflammation. Body weight (and by inference, age) directly correlated with BAL concentrations at TP and PGD₂ and inversely correlated with LTC₄/D₄/E₄ and % eosinophils. Significant correlations were found between PGD₂ vs. TP (r = 0.54, p < .001), histamine vs. % eosinophils (r = 0.45, p = 0.03), and % macrophages vs. % neutrophils (r = – 0.76, p < .001). R_L and E_L did not correlate with BAL measurements of cells or mediators. A second group of 9 animals was lavaged, permitted to recover, and re-lavaged 2 weeks later, with no significant changes noted in lung mechanics, BAL cell profiles, or mediators between study days. These data demonstrate that some baseline BAL inflammatory indices in the GP correlate well with body weight and with each other and that baseline BAL measurements of inflammatory mediators may vary with size or age of the animal, an important consideration in studies using the GP for BAL measurements of inflammatory mediators. The data further document the reproducibility and feasibility of reintubating and lavaging the same animal over a period separated by 2 weeks without having to sacrifice the animal.