Effects of local heating of the testis on testicular blood flow and testosterone secretion in the rat

Exposure of one or both testes of rats to heating at 43 degrees C for 30 min resulted in a significant reduction in blood flow per testis, as measured using microspheres. The effects on the testes of unilateral and bilateral heating were similar, although the changes in FSH levels in peripheral blood were in general less marked after unilateral heating. Testicular blood flow fell, along with testicular weight, beginning at 2-4 days and reaching minimum values 14-21 days after heating. Both blood flow per testis and testicular weight were beginning to recover 35 days post-heating and blood flow per testis was normal by 56 days following heat treatment, although testicular weight was still slightly reduced at that time. Heating one or both testes to 42 degrees C produced similar but smaller responses 21 days later, whereas temperatures of 41 degrees C or lower were without effect on the parameters measured, except for some rises in serum LH and FSH. With slight reductions in blood flow, there were corresponding increases in testicular venous testosterone concentration so that testosterone secretion was unaffected. Further reductions in blood flow at 14 and 21 days after heating to 43 degrees C were not fully compensated by an increase in the concentration of testosterone in testicular venous blood, with the result that testosterone secretion fell.