[Thermal effect on alpha 1-adrenoceptors in the guinea-pig vas deferens: histological and binding studies]

To study the mechanism of thermotherapy on benign prostatic hyperplasia, we examined thermal effects on alpha 1-adrenoceptors in the guinea-pig vas deferens. The histological changes in the muscle cells after thermal exposure were also examined by electron microscopy.

The guinea-pig vasa deferentia were pretreated at 4 degrees C (control group), 43 degrees C, 50 degrees C, and 55 degrees C (heated group) for 1 hour and returned to 37 degrees C for 1 hour or 2 hours. Radioligand binding assay for alpha 1-adrenoceptors was performed by an incubation of [3H]prazosin with the crude membrane fraction from vasa deferentia. The dissociation constant (Kd) and the number of binding sites (NBS) of alpha 1-adrenoceptors were calculated from Scatchard analysis. The histological changes in the muscle cells were also examined at 4 degrees C, 40 degrees C, 50 degrees C, and 55 degrees C for 1 hour by electron microscopy.

Kd and NBS did not change at 43 degrees C, but declined significantly above 50 degrees C for 1 hour. The changes in Kd and NBS above 50 degrees C for 1 hour did not recover after returning to 37 degrees C for 1 hour or 2 hours. Electron microscopic observations revealed a loss of myofilaments and dark staining of nuclear chromatin of the smooth muscle cells after thermal exposure above 50 degrees C.

The binding ability of [3H]prazosin to alpha 1-adrenoceptors declined after thermal exposure above 50 degrees C. Also, the muscular damages were observed histologically after thermal exposure above 50 degrees C. These results indicated that the irreversible decrease in NBS and the disruption of smooth muscle fibers were associated with the thermotherapy.