[Changes of contractility and relaxation of corpus cavernosum in hyperlipidemic rabbit in vitro].
OBJECTIVE
To investigate the mechanisms of erectile dysfunction induced by hyperlipidemia through studying the changes of contractility and relaxation of corpus cavernosum in hypercholesterolemic rabbit in vitro.


METHODS
New Zealand white rabbits were randomly divided into control and experiment groups. The control group (n = 20) received a regular diet for 8 weeks while the experimental group (n = 20) were fed a 1% cholesterol diet for 8 weeks. The authors conducted isometric tension studies with phenylephrine, endothelium-dependent vasodilators (acetylcholine), endothelium-independent vasodilators (sodium nitroprusside) and rho kinase inhibitor (Fasudil) on isolated strips of corpus cavernosum.


RESULTS
The weight and total serum cholesterol significantly improved (P < 0.01) in experimental group as compared with the non-fed experimental group. The total serum cholesterol significantly improved (P < 0.01) in experimental group as compared with the control group. The contractility responses to phenylephrine in experiment group in doses (0.5, 1, 5, 10, 50, 100 micromol) were 4.79% +/- 2.00%, 8.84% +/-2.95%, 12.81% +/- 3.77%, 14.63% +/- 5.38%, 25.01% +/- 6.14% and 34.69% +/- 8.53% respectively. The contractility responses to phenylephrine in control group were 1.00% +/- 0.3%, 2.60% +/- 0.72%, 4.28% +/- 1.27%, 5.91% +/- 2.09%, 6.49% +/- 4.02% and 5.64% +/- 11.87% respectively. The contractility responses to phenylephrine significantly improved (P < 0.01) in experimental group in these doses as compared with the control group. The relaxation responses to acetylcholine in experimental group in doses (1, 10 and 100 micromol) were 36.28% +/- 4.71%, 48.81% +/- 4.36% and 56.27% +/- 11.93% respectively. The relaxation responses in control group were 48.04% +/- 4.78%, 69.12% +/- 5.27% and 78.23% +/- 5.30% respectively. There was significant reduction (P < 0.01) in experimental group in these doses as compared with the control group. No difference were found among the two groups in the relaxation response to sodium nitroprusside. The relaxation responses to fasudil in experimental group in doses (0.25, 1.25, 2.5 and 12.5 micromol) were 1.56% +/- 0.43%, 5.03% +/- 1.02%, 8.28% +/- 1.35% and 16.77% +/- 3.57% respectively. The relaxation responses in control group were 4.69% +/- 1.23%, 10.39% +/- 2.05%, 15.08% +/- 3.04% and 25.22% +/- 3.72% respectively. There was significant reduction (P < 0.01) in experimental group in these doses as compared with the control group.


CONCLUSIONS
The improvement of cavernous smooth muscle contractility and the impairment of cavernous smooth muscle relaxation in response to endothelium-mediated stimuli are the mechanisms of erectile dysfunction induced by hyperlipidemia.
Rao
Ke
K
Department of Urology, Tongji Hospital, Tongji Medical College of Huazhong University of Science and Technology, Wuhan 430030, China.
Liu
Ji-Hong
JH
Chen
Rui-Bao
RB
Zhang
Hui-Ping
HP
Wang
Tao
T
Wang
Shao-Gang
SG
Yang
Wei-Min
WM
Ye
Zhang-Qun
ZQ
D000818:Animals; D006949:Hyperlipidemias / Q000503:physiopathology*; D008297:Male; D009119:Muscle Contraction; D009126:Muscle Relaxation; D009130:Muscle, Smooth / Q000503:physiopathology*; D010413:Penis / Q000503:physiopathology*; D011817:Rabbits