Ginsenoside Rg3 improves erectile function in streptozotocin-induced diabetic rats.

INTRODUCTION: Ginsenoside Rg3 is one of the active ingredients isolated from Panax ginseng C.A. Meyer. Previous studies demonstrated that Rg3 has antioxidant and neuroprotective abilities.

AIM: The purpose of this study was to evaluate the protective effect of Rg3 on erectile function in streptozotocin (STZ)-induced diabetic rats.

METHODS: Two-month-old Sprague-Dawley male rats received a one-time intraperitoneal (IP) STZ (60 mg/kg) or vehicle injection after a 16-hour fast. Three days later, rats were randomly divided into four groups and were treated with daily gavage feedings of a mix of distilled saline water and 0.5% carboxymethylcellulose or Rg3 dissolved in the mix at doses of 10 mg/kg and 100 mg/kg for 3 months. A sham group underwent IP injection of saline followed by daily gavage of the above mix for 3 months.

MAIN OUTCOME MEASURE: Erectile function was assessed by cavernosal nerve electrostimulation at 3 months. The penis was then harvested and deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was performed. Western blot was performed to examine cleaved caspase-3, platelet endothelial cell adhesion molecule (PECAM)-1, and smooth muscle actin (SMA). Neural regeneration was measured by nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase staining. Superoxide dismutase (SOD) and malondialdehyde (MDA) levels were detected by colorimetry.

RESULTS: In the negative control group, the functional evaluation showed a lower mean intracavernosal pressure (ICP) with cavernosal nerve stimulation than in the sham group; there was a significant change in the expression of cleaved caspase-3, bcl-2, bcl-xl, PECAM-1, and SMA, as well as in the SOD and MDA production in the corpus cavernosum. Histological analysis of specimens stained for NADPH showed a significant change in the staining quality of the neurons in the dorsal nerves; TUNEL showed a greater apoptotic index in corpus cavernosum cells. With daily oral gavage with 100 mg/kg Rg3, the ICP/mean arterial pressure value was significantly higher than in the controls. The level of cleaved caspase-3, bcl-2, bcl-xl, PECAM-1, and SMA and the number of positively stained nerve fibers tended to revert to normal after Rg3 treatment. The apoptotic index in corpus cavernosum cells was lowered.

CONCLUSION: Oral gavage with Rg3 appears to both prevent degeneration of neurons in the dorsal nerves and exert an antioxidant effect in the corpus cavernosum of rats.