The Study Of Mechanism And Drug Intervention On Chronic Renal Failure Related Erectile Dysfunction

Background : Chronic renal failure (CRF) occurs as a clinical syndrome. 57.9% of CRF cases are associated with erection dysfunction (ED). For patients at the terminal phase of nephropathy, ED incurrence rate accounts for 85.4%, including 25.4% of complete ED, 35.4% of medium ED and 24.6% of slight ED. 52.6% of patients at the terminal phase of nephropathy, who are below the age of 50 are associated with ED, while 70.5% of those patients above 50 are meanwhile ED patients . ED incidence after renal transplantation rate is about 48.9%. ED has become one of important factors negatively influencing the patient's life. Apart from associated variables (e.g. age and sex), ED can be an independent contributor to life quality. Lagged-behind study on the mechanism of CRF related ED has to some extend hindered the clinical treatment.Penile erection is performed at the mandate of neuroendocrine system and realized through the transformation from L-arginine to NO and finally cGMP. NOS, as the key enzyme in the process of this transformation, catalyzes the transformation from L-arginine to L-citrulline and NO. NO then activates guanylate cyclase(GC )to generate cyclic guanosine monophophate(cGMP), which leads to the laxity of smooth muscle in the corpus cavernosum, and the lowerness of blood tension and eventually penile erection. NO, featured by chemical instability and short half life is hard for direct measurement. And thus the metallization of NO is generally tested through measurement of NOS. Gap junction is a special membrane structure linking two neighboring cell. Gap junction intercellular communication (GJIC) facilitates the exchange of information, energy and substances, participates the metabolic couple in intercellular substantial exchange and electronic couple in electronic signal transferring, and plays a regulating role in the whole physiological process of cellular metabolism, homeostasis, and cell differentiation. Gap junction in the corpus spongiosum smooth muscle cell is mainly composed of connexin43(CX43) , which through electronic couple and metabolic couple connects the numerous cells in the corpus spongisum smooth muscle as a functional entity to regulate the synchronic diastole among smooth muscle cells, induce the relaxation of smooth muscle of corpus cavernosum and maintain penile erection.As with the rapid social development, the medication of chronic renal failure keeps refining, so as the medical equipments in this regard. The life span and life quality of CRF patients has been greatly improved as a result. The prevention and treatment of CRF induced erection dysfunction is drawing increasing attention and it then arises as an important topic to quest more effective and safer medicament for CRF induced erection dysfunction.The present study, therefore, attempts to observe the effect on rat's erectile function caused by chronic renal failure and to explore the pathophysiology of CRF related ED through measuring the expression of NOS gene and connexin 43(CX43) in CRF rat's corpus cavernous. It is hoped that the pathophysiological study can provide theoretical basis for clinical treatment on CRF related ED. To observe the effects of various drugs on relaxation responses in chronic renal failure (CRF) rabbit cavernosal strips, so as to provide theoretical guidance for the selection of most effective drugs for CRF reduced erection dysfunction. Part 1 The Mechanism Study of Chronic Renal Failure RelatedErectile DysfunctionObjectiveCRF experimental models were established through operation. The effect of chronic renal failure on rat's erectile function were observed. Through testing the genetic expression of nNOS and eNOS in the rat corpus cavernosum and the expression of CX43 in the rat corpus cavernosum,the mechanism of erection dysfunction caused by chronic renal failure were investigated . The theoretical study base were set up for CRF-related ED.Methods1. Both the rats from control group (NCRF group, n=6, the bilateral kidney were only freed and the fat around kidney were stripped, but there were no nephrectomy.) and experimental group (CRF group, n=30, in one stage, the right kidney was done nephrectomy and he left kidney was done 2/3 nephrectomy) were examined the levels of serum creatinine (Scr) and blood urea nitrogen (BUN) in the blood at 12th week after the resection surgery. The rats from NCRF group and NCR group were injected with a low dose (80μg/kg.d) of apomorphine (APO) at 12th week after the resection surgery in order to measure correspondent penile erections.2. Reverse transcriptase polymerase chain reaction (RT-PCR) was thereafter conducted to examine the gene expression of endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) in the rat corpus cavernosum in 12th week after the resection surgery.3. Western blot method was thereafter conducted to examine the expression of connexin 43(CX43) in the rat corpus cavernosum in 12th week after the resection surgery.Results1. NCRF group witnessed one death whereas CRF group saw 5 cases of death. The levels of BUN and Scr in CRF group were 27.35±2.51 mmol/L,126.62±10.05 umol/L while The levels of BUN and Scr in NCRF group were5.40±0.42 mmol/L,51.40±4.01 umol/L, which presents a significant difference(P < 0.05). Penile erection ratio of the CRF group is 7/25 while that of NCRF is 5/5, which presents a significant difference(P< 0.05). In terms of penile erection frequency, the average of CRF group is (1.0±0.0 ) while that of NCRF group is as high as (2.2±0.8) , which also shows notable difference (P < 0.05).2. With regards to the gene expression of nNOS in the rat corpus cavernosum, the average of CRF group (0.21±0.07 ) is similarly lower than that of NCRF group(0.40±0.08) with significant difference (P < 0.01). As to the gene expression of eNOS in the rat corpus cavernosum, the RT-PCR results showed that the average of CRF group (0.28±0.08 ) is lower than that of NCRF group (0.67±0.13) with notable difference (P< 0.01).3. With regards to the expression of CX43 in the rat corpus cavernosum, the average of CRF group (0.18±0.08 ) is similarly lower than that of NCRF group(0.53±0.27) with significant difference (P < 0.01).Conclusions1. There were no death rate increase in CRF experimental models established by resecting off 5/6 kidney from male sprague-dawley (SD) rats in one stage . Establishment of animal experimental models by resecting off 5/6 of rat kidney in one stage is of high feasibility. After the injection of APO, CRF group reported less erection rate and erection frequency than NCRF group, which shows CRF significantly reduces the erectile function of the rats.2. Expression of nNOSmRNA and eNOSmRNA in the corpus cavernosum of CRF group show apparent scarcity, compared with NCRF group. CRF-related ED bears correlation with the decrease in the gene expression of eNOS and nNOS in the rat corpus cavernosum.3. Expression of CX43 in the corpus cavernosum of CRF group show apparent scarcity, compared with NCRF group. CRF-related ED bears correlation with the decrease in the expression of CX43 in the rat corpus cavernosum. Part 2The Effect of Drug Intervention on Relaxation Responses in Cavernosal Strips of the Rabbit with Chronic Renal FailureObjectiveTo observe the effects of various medicaments on phosphodiesterase inhibitor-induced relaxation responses in chronic renal failure (CRF) rabbit cavernosal strips, so as to provide theoretical guidance for the selection of most effective drug for CRF reduced erection dysfunction.Methods10 New Zealand rabbits were performed 5/6 nephrectomy to form CRF rabbit model for the experiment. BUN and Cr levels in blood serum were measured both before the establishment of rabbit models and four weeks after the establishment. The entire penis of the experiment rabbit was removed at the end of 4-week period .The strips of corpus cavernosum smooth muscles were then exposed to papaverine, sodium nitroprussiate and tadalafil of different concentration levels to measure the ratios of relaxation responses.Results1. The Scr value at the end of 4-week period records as 126.62±10.05μmol/L, which is significantly higher than that of four weeks before, i.e 1.40±4.01μmol/L, (P<0.05). Blood serum BUN value at the end of 4-week period (27.35±2.51 mmol/L) is significantly higher than before (5.40±0.41 mmol/L) (P<0.05).2. Under the same concentration levels as 10-8 mol/L,10-7 mol/L,10-6 mol/L,10-5 mol/L and 10-4 mol/L respectively, the effects of papaverine and sodium nitroprussiate on relaxation responses in the smooth muscles of CRF rabbit cavernosal strips show no difference (P>0.05). Under the same concentration, tadalafil induce higher ratio of relation responses in the smooth muscles of CRF rabbit cavernosal strips, compared with papaverine and sodium nitroprussiate, with most significant difference occurring under the concentration indicators of 10-5 mol/L and 10-4 mol/L (P<0.01).ConclusionsThe effects of tadalafil on relaxation responses in CRF rabbit cavernosal strips highly depend on its concentration. The effect of tadalafil on relaxation responses in CRF rabbit cavernosal strips is better than that of papaverine and sodium nitroprussiate. Tadalafil may be an effective drug for treating CRF reduced erection dysfunction.