Our aim was to compare the ultrastructure of penile cavernous tissue in the spontaneous hypertensive rat (SHR) and normotensive rat, and study the relation of blood pressure with erectile function. After injection of apomorphine (APO), penile erectile frequency in 16-week-old SHR (group A) and Wistar-Kyoto rat (WKY) (group B) was observed and noted. The ultrastructure of the penile cavernous tissue was studied by scanning electron microscope and transmission electron microscope. The mean blood pressures were significantly higher in group A than in group B (P ¼ 0; 171.20710.94 and 117.60712.38, n ¼ 5, for group A and group B, respectively). After treatment of the two groups with APO, the erectile frequency in group A was significantly less than in group B (P ¼ 0.007; 0.4070.55 and 2.4071.14, n ¼ 5, for group A and group B, respectively). Significant ultrastructural pathological changes were observed in the tunica albuginea and penile cavernous tissue of SHR. The elastic fibers were decreased and the collagen fibers of the sinusoid were increased in group A. The tunica albuginea thickness (mean7s.d.) was 100.2077.22 lm and 126.0077.65 lm in group A and group B, respectively. The tunica albuginea of group A was significantly thinner than that in B (P ¼ 0.001). Some endothelial cells and smooth muscle cells exhibited damaged mitochondria, and endoplasmic reticulums and Schwann cells were degenerated in group A. Although the function of penile erection might be affected by a secondary effect related to endothelial dysfunction of hypertension, these ultrastructural pathological changes of the penile cavernous tissue might also be one of the important mechanisms of erectile dysfunction caused by hypertension.

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