Stress responses in the chemistry and mRNA abundance of the peripheral blood in the American alligator

Abstract

To monitor physiological and toxicological conditions in an endangered species, noninvasive to minimally invasive sampling methods are needed. We analyzed peripheral blood cells to determine if we could monitor some physiological responses of the American alligator following capture stress. Juvenile American alligators were restrained for 16 h to examine the stress response in plasma and blood cells. Plasma corticosterone concentrations were increased by restraint as were plasma concentrations of aspartate aminotransferase (AST), creatine kinase (CK), uric acid, and glucose; a sexually dimorphic response was seen in AST and CK concentrations. The lapse time of restraint was associated with altered messenger RNA (mRNA) levels of the glucocorticoid receptor (GCR) in red blood cells and JUN proto‐oncogene in both white and red blood cells. A two‐way cluster analysis revealed that two major clusters of factors were associated with the responses seen: (a) mRNA levels of GCR and heat‐shock proteins in both blood cells were associated with plasma corticosterone concentration, whereas (b) androgen receptors and JUN mRNA levels in both blood cells were associated with cloacal temperature and body composition. Blood cells appear to be an excellent source to examine the cellular stress response to steroid hormone signals in mRNA levels. We propose that this approach, using blood cells, could provide essential insights into the molecular responses associated with stress in reptiles as well as many other nontraditional model species, including endangered species.

Physiological stress response in free‐living Amazonian caimans following experimental capture

“…For example, C. porosus subjected to exhaustive physical activity (Seymour et al, 1985) or manual physical restraint (Franklin et al, 2003) responded with high blood lactate concentrations. Similar effects have also been reported for A. mississippiensis (Coulson & Hernandez, 1983; Kohno et al 2019). Obviously, even free‐living crocodiles are subject to some muscular workload when capturing their prey, and consequently, lactate levels tend to increase.…”

“…mississippiensis (Coulson & Hernandez, 1983;Kohno et al 2019). Obviously, even free-living crocodiles are subject to some muscular workload when capturing their prey, and consequently, lactate levels tend to increase.…”

“…All analyses were performed in duplicate. The use of this kit was previously validated for crocodilians by Finger et al (2018) and Kohno et al (2019). Serial dilutions of the plasma that contained a high content of corticosterone that was similar to the standard curve.…”

Identification and evaluation of antioxidant and reference genes for quantitative real-time PCR in blood of Caiman latirostris

“…In this work, we identify and validate reference genes to obtain reliable and accurate data in qPCR from blood of C. latirostris hatchling. The evaluation and validation of reference genes in crocodilians is limited [ 26 ] and most gene studies have used a single reference gene without evaluating the stability or the expression of other housekeepings [ 40 , 41 , 42 , 43 , 44 ].…”

“…The possibility to apply molecular gene expression markers in C. latirostris would allow us to understand the specific meaning of many alterations produced by pesticides and observed through traditional biomarkers. In this sense, we believe it is necessary to study the stability of potential reference genes under normal conditions, since there is limited information in crocodilian species [ 26 ]. The aim of this study was to evaluate the catalase ( cat ) and superoxide dismutase ( sod ) genes transcript levels in C. latirotris blood, to propose them as biomarkers of oxidative stress induced by environmental stressors.…”