Evidence against a zinc binding peptide in pilocarpine-stimulated canine prostatic secretions

Changes in serum and prostatic zinc concentrations in rats after intraprostatic injection of zinc: Comparison of two forms of zinc delivery

BACKGROUND

We investigated changes in zinc concentrations in serum and prostatic tissue after an intraprostatic injection of zinc, and compared two forms of zinc delivery: solution and liposome.

METHODS

Ninety-six male Wistar rats were used in the study (24 controls, 72 test rats). The test animals were randomly divided into two groups and were injected intraprostatically with 2 mL of 0.04 mol/L zinc sulfate according to the form of zinc delivery. Nine rats in each test group were sacrificed 1 day, 7, 14 and 28 days after injection, and 24 normal rats were injected intraprostatically with 2 mL of distilled water as controls. Serum and prostatic zinc concentrations of each group were measured by inductively coupled plasma atomic emission spectrometry. Blood chemistries, routine urinalysis, urine culture and histopathologic examination were also performed.

RESULTS

Serum zinc concentrations did not change significantly after the intraprostatic injection of zinc. Prostatic zinc concentrations were found to be significantly greater (P < 0.05) in zinc-injected groups than in the control group. The intraprostatic injection of zinc solution and zinc liposome increased zinc levels in both ventral and dorsolateral lobes significantly. Prostatic zinc levels increased progressively following injection, reaching a peak level in 7 days and maintaining a high value throughout the experimental period. The prostatic zinc level of the 1-day zinc liposome group was higher than that of the 1-day zinc solution group, while no significant difference was observed between the solution and liposome group in 7, 14, 28 days. No abnormal findings were observed in any of the laboratory and histopathologic examinations; however, an acute inflammatory response was observed in the 1-day groups.

CONCLUSION

These findings suggest that an intraprostatic injection of zinc in normal rats increases and maintains the prostatic zinc level for at least 4 weeks without causing any systemic or local toxicities. These findings suggest the potentially important clinical applicability of local zinc to the treatment of chronic prostatitis.

Antibacterial effect of intraprostatic zinc injection in a rat model of chronic bacterial prostatitis

High levels of prostatic zinc are associated with prostatic antimicrobial activities and are depressed in patients with chronic prostatitis. We investigated the inhibition of bacterial growth in the rat prostate with chronic prostatitis after intraprostatic injection of zinc and compared two different types of zinc delivery. Ninety male Wistar rats were used in the study. Experimental chronic bacterial prostatitis was induced by instillation of bacterial suspension (Escherichia coli 10(8) per ml) into the prostatic urethra. Animals were followed for 4 weeks and then injected intraprostatically with either 0.2 ml of zinc liposome (ZL) or zinc solution (ZS) (0.04 M zinc sulphate) or 0.2 ml of phosphate-buffered saline (PBS) for the controls. Ten rats in each group were sacrificed 4, 6 and 8 weeks after injection. The inhibition of inflammation and its consequences were analyzed microbiologically and histologically. Prostatic zinc concentrations were measured by inductively coupled plasma atomic emission spectrometry. Microbiological culture of the prostates demonstrated bacterial growth inhibition by the intraprostatic injection of zinc. The average infection rates and mean log(10) cfu/g of the zinc-treated groups were significantly lower than those of the controls. The histopathology showed resolving prostatitis in zinc-treated groups compared with the controls. Prostatic zinc levels were higher in the zinc-treated groups than in the controls 4 and 6 weeks after zinc injection (P<0.05). However, the ZL and ZS groups were found to be effectively identical in terms of prostatic zinc levels, bacterial cfu, and histological findings throughout the experiment period. The intraprostatic injection of zinc inhibited bacterial growth by increasing zinc levels in the rat prostatitis model. Our results suggest that the local application of zinc to the prostate may be a new treatment for chronic bacterial prostatitis at the point of its pathogenesis.

Prostatitis

Several distinct types of prostatitis, or prostatitis syndromes, are now recognized. The most common forms include acute and chronic bacterial prostatitis, nonbacterial prostatitis, and prostatodynia. Bacterial prostatitis, caused mainly by coliform bacteria, Pseudomonas, and Enterococcus faecalis, is often difficult to cure and usually requires extended therapy (4-16 weeks) with an appropriate antimicrobial agent that achieves therapeutic levels in the prostatic secretory system. About 90% of men with prostatitis have nonbacterial prostatitis or prostatodynia. Nonbacterial prostatitis is an inflammation of the prostate of unknown cause. Patients with prostatodynia typically have sterile cultures and normal prostatic secretions but demonstrate an acquired voiding dysfunction on videourodynamic testing. Because nonbacterial types of prostatitis have no recognized infectious cause, treatment using antimicrobial agents is ineffective and unwarranted.