Barros Adwell C M Q, Brito L F C, Oba E, Wilde R E, Rizzoto G, Thundathil J C, Kastelic J P
Department of Animal Reproduction and Veterinary Radiology, FMVZ, UNESP, Rubiao Jr. s/n, 18618-000, Botucatu, SP, Brazil.
Agriculture and Agri-Food Canada, Lethbridge Research Centre, PO Box 3000, T1J 4B1, Lethbridge AB, Canada.
Theriogenology. 2018 Aug;116:12-16. doi: 10.1016/j.theriogenology.2018.04.022. Epub 2018 Apr 26.
Two experiments were done in bulls to determine: total testicular blood flow, testis oxygenation and heat, and effects of ambient temperature on testicular temperatures and blood flow. In Experiment 1, arterial blood flow to testes and testicular oxygenation and heat were determined in Angus bulls (n = 8). Blood temperature and hemoglobin O saturation were both greater (P < 0.0001) in the testicular artery than in the testicular vein (39.2 ± 0.2 vs 36.9 ± 0.4 °C and 95.3 ± 0.7 vs 42.0 ± 5.8%, respectively; mean ± SEM). Based on testicular blood flow of 12.4 ± 1.1 mL/min and an arterial-venous temperature differential of 2.3 °C, blood contributed 28.3 ± 5.1 cal/min of heat to the testis, whereas heat produced by testicular metabolism was estimated at 5.8 ± 0.8 cal/min (based on O consumption of 1.2 ± 0.2 mL/min). In Experiment 2, effects of three ambient temperatures (5, 15 and 35 °C) on testicular blood flow and temperatures were determined in 20 Angus bulls. At 35 versus 5 °C, there was greater testicular blood flow (8.2 ± 0.9 versus 4.9 ± 0.7 mL/min/100 g of testicular tissue, P < 0.05), and higher scrotal subcutaneous and intratesticular temperatures (P < 0.01). In conclusion, arterial blood flow was the main source of testicular heat, testes were close to hypoxia, and increased ambient temperature significantly increased scrotal subcutaneous and intratesticular temperatures, as well as testicular blood flow. These studies gave new insights into scrotal/testicular thermoregulation in bulls; they confirmed that testes are nearly hypoxic, but challenged the long-standing paradigm that testicular blood flow does not increase when testes become warmer.
进行了两项针对公牛的实验，以确定：睾丸总血流量、睾丸氧合与热量，以及环境温度对睾丸温度和血流量的影响。在实验1中，测定了安格斯公牛（n = 8）的睾丸动脉血流量、睾丸氧合与热量。睾丸动脉中的血液温度和血红蛋白氧饱和度均高于（P < 0.0001）睾丸静脉（分别为39.2 ± 0.2 vs 36.9 ± 0.4°C和95.3 ± 0.7 vs 42.0 ± 5.8%；平均值±标准误）。基于12.4 ± 1.1 mL/min的睾丸血流量和2.3°C的动静脉温差，血液为睾丸提供了28.3 ± 5.1 cal/min的热量，而睾丸代谢产生的热量估计为5.8 ± 0.8 cal/min（基于1.2 ± 0.2 mL/min的耗氧量）。在实验2中，测定了20头安格斯公牛在三种环境温度（5、15和35°C）下对睾丸血流量和温度的影响。与5°C相比，在35°C时，睾丸血流量更大（8.2 ± 0.9 vs 4.9 ± 0.7 mL/min/100 g睾丸组织，P < 0.05），阴囊皮下和睾丸内温度更高（P < 0.01）。总之，动脉血流量是睾丸热量的主要来源，睾丸接近缺氧状态，环境温度升高显著增加了阴囊皮下和睾丸内温度以及睾丸血流量。这些研究为公牛阴囊/睾丸的体温调节提供了新的见解；它们证实睾丸几乎处于缺氧状态，但对睾丸变暖时睾丸血流量不会增加这一长期存在的范式提出了挑战。
