Acute phase protein concentrations following serial procaine penicillin G injections in horses.

Abstract

BACKGROUND: Acute phase protein (APP) measurement is used to detect inflammation. Intramuscular (IM) injections could cause tissue injury and induce an acute phase response (APR). OBJECTIVES: To evaluate the effects of IM procaine penicillin G (PPG) injections on APP concentrations in horses. STUDY DESIGN: Prospective longitudinal design. METHODS: PPG was administered intramuscularly to six horses, twice daily, for 5&#x2009;days. Plasma fibrinogen (FIB), serum amyloid A (SAA), haptoglobin (HAP), creatine kinase (CK), and aspartate aminotransferase (AST) were quantified daily for 5&#x2009;days before the first injection, during the course of administration, and for 4&#x2009;days after the final dose. Analytes were quantified every other day for the remaining 16&#x2009;days. Data were compared using a parametric or non-parametric repeated measures ANOVA and a Tukey's or Mann-Whitney rank sum test, respectively. Significance was set at p&#x2009;<&#x2009;0.05. RESULTS: CK was increased over baseline (mean&#x2009;&#xb1;&#x2009;SD: 200&#x2009;&#xb1;&#x2009;74&#x2009;IU/L) on Days 1-6 (p&#x2009;<&#x2009;0.001 to p&#xa0;=&#xa0;0.02, mean&#x2009;&#xb1;&#x2009;SD: 723-1177&#x2009;&#xb1;&#x2009;355-544&#x2009;IU/L) and AST was increased above baseline (mean&#x2009;&#xb1;&#x2009;SD: 233&#x2009;&#xb1;&#x2009;58&#x2009;IU/L) on Days 2-7 and 10 (p&#x2009;<&#x2009;0.001 to p&#xa0;=&#xa0;0.05, mean&#x2009;&#xb1;&#x2009;SD: 307-437&#x2009;&#xb1;&#x2009;79-146&#x2009;IU/L). Increased FIB was noted over baseline (mean&#x2009;&#xb1;&#x2009;SD: 177&#x2009;&#xb1;&#x2009;30&#x2009;mg/dl) on Days 6-8 and 10 (p&#xa0;=&#xa0;0.02 to p&#xa0;=&#xa0;0.03, mean&#x2009;&#xb1;&#x2009;SD: 234-252&#x2009;&#xb1;&#x2009;33-49&#x2009;mg/dl). SAA was increased above baseline (mean &#xb1;&#x2009;SD: 4.7&#x2009;&#xb1;&#x2009;2.9) on Day 6 (p&#xa0;=&#xa0;0.02, mean&#x2009;&#xb1;&#x2009;SD: 113&#x2009;&#xb1;&#x2009;186&#x2009;&#x3bc;g/ml). There was no change in HAP. MAIN LIMITATIONS: Healthy horses were used, small sample size, and a lack of a negative control group. CONCLUSIONS: Serial intramuscular procaine penicillin G (IM PPG) injections may result in increased positive APP concentrations in horses and this must be considered when these test results are interpreted.