Effect Of Low Androgen Status On Galanin And GalRs In Rat Corpus Cavernosum And Their Relationship With Erectile Function

Background:The exact mechanism of erectile dysfunction(ED)caused by hypoandrogen is not completely clear.The combination of galanin and Gal Rs affects the contraction and relaxation of smooth muscle cell(SMC)through its downstream pathway.However,the effect of androgen on galanin and Gal Rs and the relationship between galanin and erectile function under hypoandrogen is still unclear.Objectives:To explore whether low testosterone level damages the erectile function of rat by regulating the expression of galanin and Gal R and the relationship between galanin and erectile function.Materials and methods:Thirty-six male Sprague Dawley(SD)rats,8weeks of age,were randomly grouped into 6(n=6):sham operation group(sham group),castration group(cast group),testosterone replacement group(cast+T group),sham+transfection group(sham+LV Gal group),castration+transfection group(cast+LV Gal group)and castration+empty transfection group(cast+LV vector group).The rats in castration group were excised the bilateral testis and epididymis and the scrotum skin was sutured,while only the scrotum was incised and sutured in the rats of sham group.After castration,testosterone propionate(30 mg/Kg)was injected subcutaneously into the rats in the cast+T group every other day.At the 5 weeks of surgery,lentivirus vector carrying the galanin gene(2x10~8TU/m L,10μl)was injected into the penile cavernous tissue of rats in the transfection group.The rats in the empty transfection group were injected with the same doses and titers of empty vector.After the 6 weeks of castration,the intracavernosal pressure(ICP),mean arterial blood pressure(MAP),nitric oxide(NO),serum T concentration,galanin,Gal R1-3,ROCK1,ROCK2,e NOS and p-e NOS in the rat penile tissues were measured.Results:The ICPmax/MAP was significantly lower in the cast group(3v:0.32±0.018;5v:0.43±0.033)compared to the sham group(3v:0.63±0.029;5v:0.74±0.02)and the cast+T group(33v:0.64±0.023;5v:0.75±0.048)(P<0.01);The ICPmax/MAP was significantly increased in cast+LV Gal group(3v:0.45±0.025;5v:0.55±0.038)compared with that in the cast group(3v:0.32±0.018;5v:0.43±0.033)(P<0.01)under 3v and 5v electrical stimulation;Serum testosterone and NO concentration of rat corpus cavernosum were significantly lower in the cast group(1.44±0.37nmol/L;4.96±0.61μmol/gprot)and cast+LV vector group(1.32±0.31nmol/L;6.86±3.17μmol/gprot)compared to the sham group(20.37±0.96nmol/L;13.90±0.87μmol/gprot)and cast+T group(19.37±1.60nmol/L;14.28±0.94μmol/gprot),respectively(P<0.01).When compared to the sham and cast+T group,the serum testosterone and NO content of corpus cavernosum of rats in the cast+LV Gal group was significantly decreased(1.59±0.2 nmol/L;12.75±3.27μmol/gprot)(P<0.01).NO concentration of rat corpus cavernosum in the cast+LV Gal group was significantly higher than that in the cast group and cast+vector group.IHC results showed that galanin and Gal R1-3 were respectively distributed in the cytoplasm and membrane of ECs and SMCs of penile cavernous tissue in rats.The expression of galanin and Gal R1-3 in the penile cavernous tissue of rats was significantly lower in the cast group than that in the sham and cast+T group(P<0.01).Compared with the rats in the cast group and cast+vector group,the expression of galanin in the rat corpus cavernosum was significantly increased in the cast+LV Gal group(P<0.01).The expression of Gal R1-3 in the penile cavernous tissue of rats in the cast+LV Gal group were no significant changes compared with the rats in the cast group and cast+vector group.Western blot results showed that when compared to the sham and cast+T group,the expression of galanin,Gal R1-3 and p-e NOS/e NOS in penile cavernous tissue of rats in the cast group and cast+vector group were significantly decreased(P<0.05)and the expression of ROCK1 and ROCK2 in penile cavernous tissue of rats in the cast group and cast+vector group were significantly increased(P<0.05).When compared with the cast group and cast+vector group,the expression of galanin and p-e NOS/e NOS were significantly increased(P<0.05)and the expression of ROCK1 and ROCK2 were significantly decreased(P<0.05)in the cast+LV Gal group.Conclusion:Low androgen status impairs erectile function of rats by inhibiting the expression of galanin and Gal R1-3,upregulating the level of ROCK1 and ROCK2,inhibiting the e NOS/NO signaling pathway and reducing NO synthesis and release in corpus cavernosum.Upregulation of the expression of galanin in rat penile cavernosum tissue by intracavernous injection of lentiviral vector carrying the galanin-specific overexpression gene can inhibit the high expression of ROCK1 and ROCK2,activate the e NOS/NO signaling pathway and alleviate erectile function in castrated rats.