Diabetes-related Changes Of AQPs Expression In Rat Vaginal Tissues

Objective:The prevelance of female sexual dysfunction ishigher.Recently,sexual dysfunction in women with diabetes mellitus isconcerned.The decreased vaginal lubrication is a common reason ofsexual dysfunction in women with diabetes mellitus,but the mechanism isunknown.Water channel proteins,aquaprins(AQPs),are membraneproteins that facilitate transcellular transportation of water and smallsolutes.The aim of this study is to investigate the Diabetes-relatedchanges of AQPs expression in rat vaginal tissues,and to demonstrate thepossible reason of the decreased vaginal lubrication,and facilitate theclinic treatment for sexual dysfunction in women with diabetes mellitus.Methods:Female Sprague-Dawley rats(n=40) were randomly dividedinto4experimental groups: group A(4-week control group),groupB(8-week control group),group C(4-week diabetic group) and groupD(8-week diabetic group).The models of diabetic rat were established bya single intraperitoneal injection of1%Streptozotocin（Sigma,America）. Glucose and estradiol concentrations in rat bloodplasma were determined before the experiment.The animals wereanesthetized with3%pentobarbital sodium,and a4-cm lower midline abdominal incision was made.The pelvic nerve identified on thepostrolateral aspect of the rectum.A RM6280c multichannel physicalsignal collection system electrode was placed around the vaginal branchof the pelvic nerve.Unilateral pelvic nerve stimulation was accomplishedwith7V of pulse amplitude,16Hz frequency and0.8milliseconds pulseduration.Vaginal secretion were measured by the use of a pre-weightedcotton tipped stick,The pelvic nerve was stimulated for60seconds,andthe cotton tipped stick was placed in vaginal for1minute.Subsequently,the cotton tipped stick was removed andweighed.Vaginal lubrication was assumed to be the weight of the fluidabsorbed by the cotton swab.To prevent contamination with urine,thebladder contents were removed through needle.The throughout vaginalwall was dissected.The vaginal tissue was grinded use liquid nitrogen topowder.The protein was extracted.The cell homogenates were separatedby12%SDS-polyacrylamide gel electrophoresis.The relative expressionof AQP1,AQP2,AQP3was examined by immunoblot analysis. Results:The serum concentrations of glucose were higher in group C（26.42±3.09mmol/l） and group D（27.74±1.46mmol/l） than groupA（6.6±0.45mmol/l）and group B（6.14±0.75mmol/l）(P＜0.05).The serumconcentrations of estradiol in all groups were no significant difference(p＞0.05).Estimated vaginal secretion after nerve stimulation was lower inboth group C(2.7±0.67mg) and group D(2.5±1.03mg) than group A(5.7±1.23mg) and group B(5.5±1.08mg) respectively （P＜0.05）.Western Blotting showed that the expression of AQP1,AQP2, andAQP3isoforms was decreased significantly in both group C and groupD(P＜0.05). Conclusions:The vaginal secretion of diabetic rats waslower than normal rats.The decrease of vaginal lubrication in diabetic ratsmay be the result of down-regulation of AQP1,2,and3isoforms.Theexpression of AQP1,2and3may be modulated by the serum glucoselevel.