19-norandrostenedione (19-NORA) is known as an intermediate in the metabolic pathway from androstenedione to estrone. Administration of esterified 19-nortestosterone, anabolic steroid, reduces serum gonadotropin and testosterone concentration,
and
results in reversible azoospermia in men. 19-NORA have been isolated from testis, but its function in testis is not clear yet. Therefore, this study was designed to determine the effect of 19-NORA on steroidogenesis and on spermatogenesis.
19-NORA was administrated by single intratesticular injection on adult male rats weighing 350-400g in dose of 1mg/50μl. The serum and testis were collected on 1, 3, 7, 12, 48hr after injection. The histological differences in testis were
observed
by
routine paraffin method. The concentrations of testosterone and estradiol in serum and in left testis were determined by the conventional radioimmunoassays. One hour after 19-NORA treatment, serum concentrations of testosterone and estradiol
increased
significantly, compared to those of pre-treated (0hr) group, and reduced gradually to the control level on 7 hour after injection. The concentration of testosterone in left testis increased slightly 1 hour after injection, and estradiol level
increased
significantly (p<0.05). Also, testosterone and estradiol level of control group revealed no difference with pre-treated (0hr) group. Gonad index, structure of seminiferous tubules, and the number of step 7th spermatid were simillar to control
group.
The present study suggests that the elevation of testosterone level results from increment of estradiol followed by the rapid metabolism of 19-NORA at 7 hour after injection, and then testosterone concentration may be recovered to control level
by
feedback mechanism of hypothalamus-hypothysis-testis axis.
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