Effects of sauna-like heat stress on the respiratory tract ciliogenesis and cilia in adult male rats.

Rats were exposed daily to +85 degrees C for 10 min for 60 d; half of them were exposed to -15 degrees C for 8.5 min each time immediately after heating. Rats were sacrified in groups at intervals of 20 d. Their respiratory cilia were studied with the electron microscope. In ciliogenesis, and increase was noted in the nunmber of fibrogranular areas and basal bodies deep in the cytoplasm. In the cilium the 9+2 pattern was reduced to 8+2; electron-dense material appeared at the ciliary base of other cilia. The last two changes were reversible. Only the trachea and main bronchus were affected. The ciliary changes appeared only after heating followed by cooling at -15 degrees C; those related to ciliogenesis appeared with and without cooling at -15 degrees C. Heat seemed to be a non-specific stimulus, but the role of the systemic effects of hyperthermia must be considered.