Pronounced induction of testicular PGF(2 alpha) and suppression of testosterone by cadmium-prevention by zinc.

• In order to investigate the effects of cadmium (Cd) on testicular prostaglandin F(2 alpha) (PGF(2 alpha)) production, adult male Sprague-Dawley rats were exposed to CdCl(2) by subcutaneous injections. Dose-response as well as temporal-response experiments were performed, and PGF(2 alpha) levels were determined by radioimmunoassay (RIA). The highest cadmium dose (10 micromol/kg) caused a dramatic elevation of testicular PGF(2 alpha), which was established to occur 48 h after exposure. At this point of time, cadmium-treated animals displayed PGF(2 alpha) levels 16.7 times higher than saline-injected controls. No significant differences were found with the lower doses used (1 and 5 micromol/kg). In addition, the influence of pre-treatment with zinc (Zn) was assessed. The very strong stimulatory effect on PGF(2 alpha) synthesis (22.3-fold) detected after exposure to 20 micromol/kg cadmium, was completely absent in the group given zinc (1 mmol/kg) prior to cadmium exposure. Plasma testosterone concentrations were determined in the three experiments, and all groups with strongly elevated PGF(2 alpha) levels showed drastically lowered concentrations of testosterone. Zinc pre-treatment abolished not only the cadmium-induced rise in PGF(2 alpha) but also the testosterone reduction. Additionally, cadmium was found to inhibit the expression of steroidogenic acute regulatory protein (StAR), which is responsible for the rate-limiting step in steroidogenesis. The present findings establish that cadmium can cause a strong induction of testicular PGF(2 alpha) production, which might help to explain the well-known antisteroidogenic effect of this heavy metal. Such an inhibitory effect could be due to reduced levels of StAR.

Nyckelord

Analysis of Variance

Animals

Cadmium Chloride

antagonists & inhibitors

toxicity

Dinoprost

biosynthesis

Leydig Cells

drug effects

metabolism

Male

Phosphoproteins

drug effects

metabolism

Radioimmunoassay

Rats

Rats

Sprague-Dawley

Testis

drug effects

metabolism

Testosterone

biosynthesis

blood

Zinc

pharmacology

Cadmium; Rat; Prostaglandin F2α (PGF2α); Steroidogenic acute regulatory protein (StAR); Testis; Testosterone

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