Increased flow of testicular blood plasma during local heating of the testes of rams

Abstract

After removal of the scrotal skin, one testis of each of 12 adult anaesthetized rams was kept at 33°C for 60 min, then heated either to 36°C for 60 min and then to 39°C for 60 min, or to 36°C for 120 min and then returned to 33°C for 100 min, while the other testis was maintained at 33°C. Flow of testicular blood plasma as measured every 10 min using the technique of dilution of sodium p-aminohippurate. When the temperature of the testis was raised to 36°C, flow of blood plasma gradually increased and reached a higher than normal rate at the end of the first hour, without any further increase during the second hour. The increase in mean flow rate was 25.8 ± 3.4% (mean ± SEM) during the second hour at 36°C, and 77.1 ± 12.8% during the hour at 39°C, compared with the respective values at 33°C. No significant changes were seen in testicular lymph flow determined by collection for 10 min in four rams at 36°C (60 min) and then at 39°C (60 min). These results are different from those from earlier studies in which total blood flow was unchanged when the scrotum and testes were heated. The difference could be related either to lack of heating of the scrotum or to the lower temperatures used in the present study. Changes in the flow of arterial blood bypassing the testis through arterio-venous anastomoses in the spermatic cord might be involved, as a result of heating of the testes.