Assessing the link between skin Aquaporins and morphological attributes under simulated heat stress conditions: A comparative investigation between hair and wool sheep breeds

Abstract

A comprehensive understanding of the functions of Aquaporins (AQPs) is indispensable for elucidating physiological adjustments to varied habitats and addressing water balance complexities amid environmental fluctuations. This experiment endeavors to investigate the relationship between cutaneous AQPs and morphological traits in two sheep breeds with differing haircoat textures, the Naimi and Najdi, under simulated heat stress conditions. Ten male lambs from each breed were housed individually in controlled environments and subjected to cyclic heat stress mimicking summer conditions for six weeks. Sweating rates (SR) were measured biweekly, and skin and coat samples were collected for analysis in the final week. Additionally, the mRNA expression levels of Aquaporin 1 (AQP1), Aquaporin 3 (AQP3), and Aquaporin 5 (AQP5) in skin tissue were assessed. Results showed a (P < 0.05) increase in skin AQPs gene expression following thermal exposure in both breeds, accompanied by elevated SR. However, the Naimi breed exhibited (P < 0.05) higher AQP1 expression levels, correlating with differences in their skin depth, coat thickness, and fleece density compared to the Najdi breed, which showed (P < 0.05) heightened AQP5 expression, consistent with their thicker hair diameter. Both breeds displayed similar upregulation of AQP3, suggesting its equivalent role in facilitating perspiration during heat stress. In conclusion, this experiment represents one of the initial inquiries into the presence of AQPs genes within the dermal layers of sheep. The involvement of both skin AQPs and sweating response might emphasizes the intricate interplay between their physical attributes and genetic predispositions in coping with heat stress, indicating a multifaceted process of thermoregulation in sheep. The obtained findings underscore the role of AQPs in helping sheep breeds with distinct coat textures adapt to environmental challenges and maintain water balance, and thus might support targeted breeding strategies for enhanced heat tolerance in arid environments.