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 hair 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. 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 AQPs gene expression following thermal exposure in both breeds, accompanied by elevated SR. The Naimi breed exhibited (P < 0.05) higher AQP1 expression levels, correlating with differences in skin depth, coat thickness, and hair density compared to the Najdi breed, which showed (P < 0.05) heightened AQP5 expression, consistent with its thicker hair diameter. Both breeds displayed similar upregulation of AQP3, suggesting its equivalent role in facilitating perspiration during heat stress. In conclusion, the involvement of both skin AQPs and sweating response emphasizes the intricate interplay between their physical attributes and genetic predispositions in coping with heat stress, indicating a multifaceted process of thermoregulation in sheep. This research highlights the importance of understanding AQPs functions in adapting to environmental challenges and maintaining water balance in diverse habitats.