Testosterone/estradiol ratio regulates NO-induced bladder relaxation and responsiveness to PDE5 inhibitors.
BACKGROUND
The efficacy of phosphodiesterase type 5 inhibitors (PDE5i) in treating lower urinary tract symptoms is supported by the extremely high expression and activity of PDE5 in male bladder. Although bladder function regulation is similar among genders, no data are available on PDE5 expression and activity in female bladder.


OBJECTIVE
To investigate sex differences in PDE5 expression and biological activity in female bladder, as opposed to the male counterpart.


METHODS
Gene and protein expression and enzymatic activity of PDE5.


METHODS
We studied gene and protein expression, and enzymatic activity of PDE5 in bladder of male and female rats. A subgroup of female rats was ovariectomized and alternatively replaced with estradiol (E2), progesterone, and testosterone (T) alone or in combination with letrozole to completely abrogate T-induced E formation. As a readout of PDE5 activity, we studied vardenafil efficacy in potentiating sodium nitroprusside (SNP)-induced relaxation in bladder of the different experimental groups.


RESULTS
SNP was three-log unit less potent in relaxing the male bladder than the female one. On the contrary, the PDE5-resistant cyclic guanosine monophosphate (cGMP) analog (Bromo-β-phenyl-1, N(2) -ethenoguanosine-3', 5'-cyclic monophosphorothioate, Sp-isomer [SP-8-Br-PET-cGMPS]) was equipotent in relaxing male and female bladder. Vardenafil was more effective in potentiating SNP-induced bladder relaxation in male than in female. Accordingly, the cGMP-hydrolyzing activity of PDE5 was higher in male vs. female homogenates. In ovariectomized female rats, with or without sex-steroid replacement, vardenafil activity in potentiating SNP-induced bladder relaxation was associated with an increased T/E2 ratio. In particular, masculinization of ovariectomized rats--by the administration of T + letrozole--dramatically increased vardenafil capacity to potentiate SNP-induced relaxation.


CONCLUSIONS
In this study, we demonstrated that PDE5 activity is more pronounced in male as compared with female bladder and that T/E ratio positively regulates responsiveness to PDE5i, thus suggesting that male bladder is a more suitable target for PDE5i than the female counterpart.
Clinical Physiopathology, Sexual Medicine and Andrology Unit, University of Florence, Florence, Italy.
Linda
L
Vignozzi
Sandra
S
Filippi
Annamaria
A
Morelli
Paolo
P
Comeglio
Ilaria
I
Cellai
Erica
E
Sarchielli
Elena
E
Maneschi
Rosa
R
Mancina
Mauro
M
Gacci
Gabriella Barbara
GB
Vannelli
Mario
M
Maggi
D000728:Androgens / Q000494:pharmacology; D000818:Animals; D047072:Aromatase Inhibitors / Q000494:pharmacology; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5 / Q000235:genetics / Q000378:metabolism; D004958:Estradiol / Q000097:blood* / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D015870:Gene Expression; D007093:Imidazoles / Q000494:pharmacology*; D000077289:Letrozole; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009570:Nitriles / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010052:Ovariectomy; D058986:Phosphodiesterase 5 Inhibitors / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D011374:Progesterone / Q000494:pharmacology; D011372:Progestins / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012737:Sex Factors; D013450:Sulfones / Q000494:pharmacology; D013739:Testosterone / Q000097:blood* / Q000494:pharmacology; D014227:Triazines / Q000494:pharmacology; D014230:Triazoles / Q000494:pharmacology; D001743:Urinary Bladder / Q000187:drug effects* / Q000378:metabolism; D000069058:Vardenafil Dihydrochloride
D000728:Androgens; D047072:Aromatase Inhibitors; D004967:Estrogens; D007093:Imidazoles; D020030:Nitric Oxide Donors; D009570:Nitriles; D058986:Phosphodiesterase 5 Inhibitors; D010879:Piperazines; D011372:Progestins; D012333:RNA, Messenger; D013450:Sulfones; D014227:Triazines; D014230:Triazoles; D009599:Nitroprusside; D013739:Testosterone; D011374:Progesterone; D004958:Estradiol; D000069058:Vardenafil Dihydrochloride; D000077289:Letrozole; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5