Effects of pulse-modulated microwave radiation and conventional heating on sperm production.

The effects on testicular function of pulse-modulated microwave radiation (PM MWR, 1.3 GHz) and of conventional heating were studied in the rat. Anesthetized adult males (Sprague-Dawley, 400-500 g) were treated then killed at specific intervals with respect to the 13-day cycle of the seminiferous epithelium. PM MWR at 7.7 mW/g (90 min) yielded a modest decline in daily sperm production (DSP) that derived primarily from effects on primary spermatocytes. PM MWR at 4.2 mW/g was ineffective. The mean intratesticular temperature during the former reached 40 degrees C and did not exceed 38 degrees C during the latter. MWR considerably in excess of 7.7 mW/g yielded decrements in virtually all germ cell types, with primary spermatocytes again being most markedly affected. Using conventional heating, intratesticular temperatures in excess of 39 degrees C for 60 min were required for significant decrements in DSP. Levels of circulating follicle-stimulating hormone and of leutinizing hormone were resistant to either treatment. We conclude that the damage threshold and the differential sensitivity of immature germ cells to PM MWR can be adequately explained by the consequent macroscopic heating.