Parathyroid hormone-related protein in rat penis: Expression, localization, and effect on cavernosal pressure

Although PTH-related protein-(1-36) [PTHrP-(1-36)] is known to be expressed in smooth muscle and to exert potent myorelaxant effects, its tonic effect s on cavernosal smooth muscle has not yet been explored. Using the RT-PCR t echnique, the present study establishes that PTHrP messenger RNA is present in microdissected corpus cavernosa in the rat. In immunohistochemical stud ies using affinity-purified antibodies to middle regions of PTHrP, immunost aining was localized throughout the penile structures, including vessels, c avernosal smooth muscle, and trabecular ftbroblasts. Strong immuno-staining for PTHrP was also detected in the dorsal nerve bundles. In anesthetized r ats, intracavernosally injected boluses of increasing doses of PTHrP-(1-36) (0.3-30 pmol in 100 mu l saline) had little effect on intracavernosal pres sure. However, they markedly potentiated the dilatory response to papaverin e (8-800 nmol), increasing the papaverine-induced intracavernous pressure b y 2.5-fold, close to the mean arterial pressure. In conclusion, the caverno sal expression of PTHrP messenger RNA, the distribution of immunoreactive P THrP throughout the structuro-functional components of the erectile apparat us and its strong potentiating action on papaverine-induced cavernosal rela xation, collectively suggest that PTHrP participates in the control of cave rnosal tone.