Renal histological and antioxidant response in Egyptian desert lizards during brumation

Desert lizards undergo hibernation (brumation) to survive extreme cold and food scarcity. This study investigated brumation-induced renal adaptations in four desert-dwelling species (Uromastyx aegyptia, Varanus griseus, Trapelus savignii, and Tarentola annularis) compared to their active states. Histological examination during brumation revealed kidney degeneration, including glomerulosclerosis, necrotic tubules, and cytoplasmic vacuolization. Morphometric analysis showed species‑specific renal changes during brumation; glomerular diameter significantly decreased in U. aegyptia as well as T. annularis but increased in V. griseus and T. savignii. Proximal tubule diameter increased in T. savignii but decreased in U. aegyptia, while distal tubule diameters increased significantly in T. savignii but decreased in U. aegyptia. Oxidative stress, indicated by malondialdehyde (MDA), increased significantly in all species during brumation. Superoxide dismutase (SOD) and catalase (CAT) activities increased with distinct patterns within each species. Furthermore, SOD expression increased by 0.77-fold, 1.79-fold, 0.12-fold, and 0.51-fold in U. aegyptia, V. griseus, T. savignii and T. annularis, respectively. CAT expression increased by 5.24-fold, 0.86-fold, and 0.35-fold in U. aegyptia, V. griseus, and T. annularis, but decreased in T. savignii by 0.90-fold. These findings indicate that desert lizards employ distinct, species-specific antioxidant strategies to mitigate renal oxidative stress induced by brumation, with obligate brumators (U. aegyptia and V. griseus) showing more consistent upregulation than facultative species (T. savignii and T. annularis), suggesting that the intensity of antioxidant defense correlates with the depth and duration of winter dormancy.