Summary. Ornithine decarboxylase (ODC) activity was measured in epididymides of 45-day-old rats. Higher ODC activity was detected in the corpus and cauda than in the caput epididymidis. Bilateral castration for 7 days caused epididymal ODC to fall to undetectable values, whereas testosterone restored activity to normal values. The effect of the androgen was significantly inhibited by cyproterone acetate. The caput was more sensitive to the action of testosterone than were the corpus and caudal segments. Unilateral castration for 4 or 8 days did not affect ODC on the control or castrated side, but the activity fell in epididymides of both sides after removal of the remaining testis. These results show that epididymal ODC activity is androgen-dependent.
M. A. de las Heras and R. S. Calandra
M. B. Campos, M. L. Vitale, R. S. Calandra and S. R. Chiocchio
Summary. The presence of 5-hydroxytryptamine (5-HT) was determined by h.p.l.c. in perchloric extracts of each isolated compartment of the adult rat testis. The testicular capsule, interstitial cells and interstitial fluid contained 5-HT, but 5-HT was not detected in the tubular compartment.
In a group of adult rats, one testis was unilaterally denervated, and the contralateral testis used as control. The superior spermatic nerve, arising from the renal plexus, was excised and 1 week after surgery 5-HT content was measured in the capsule and interstitial fluid of both testes. Denervation caused a significant fall (34%) in 5-HT content. These results indicate that at least part of the testicular 5-HT derives from a serotonergic innervation of the gonad.
Keywords: testis; rat; serotonin; innervation; interstitial fluid; denervation
M. A. de las Heras, S. I. Gonzalez and R. S. Calandra
Summary. Unilateral orchidectomy resulted in a significant decrease in tissue content of putrescine and polyamines. However, no differences were detected when the results were expressed in terms of ng g−1 tissue. At 48 h after bilateral orchidectomy, a significant decrease in putrescine content was observed, but spermidine and spermine content were unaffected. The observed decrease in putrescine was prevented by treatment with testosterone propionate, but neither spermidine nor spermine were affected. Bilateral orchidectomy resulted in a significant decrease in the tissue content of putrescine, spermidine and spermine after 7 days. Treatment with testosterone propionate increased the content of putrescine, spermidine and spermine in the epididymis by about 200%, 92% and 34%, respectively. When results were expressed as nmol g−1, a significant decrease after castration in putrescine and spermidine, but not in spermine, was observed. Treatment with testosterone propionate restored putrescine concentration, but had no effect on spermidine and spermine concentrations. In castrated rats treated with testosterone propionate, the anti-androgen flutamide abolished the effect of the androgen on putrescine and spermidine content, but there was no effect on spermine.
Acetylputrescine was not detected in the epididymis, while acetylpolyamines were detected at much lower concentrations than polyamines. After bilateral orchidectomy there was a decrease in the tissue content of all acetylpolyamines and an increase in their tissue concentration. The effect of castration on acetylpolyamine content was reversed by testosterone propionate treatment. We conclude that an active synthesis of polyamines occurs in the rat epididymis, and that this process depends upon the androgen environment. Regulation of ornithine decarboxylase activity appears to be the main step that is controlled by androgens.
Keywords: flutamide; putrescine; testosterone; spermidine; spermine; rat
M. A. de las Heras, M. O. Suescun and R. S. Calandra
Summary. After castration, there was a marked decrease in serum androgen concentration at 6 h, and a dramatic inhibition of ornithine decarboxylase (ODC) at 12 h. Administration of testosterone propionate to castrated rats at a dose of 0·05 mg/animal restored ODC activity to the normal value. However, no change was observed when intact rats were treated with testosterone even at a 40-fold higher dose, indicating that endogenous androgens present in intact rats are far in excess for maintenance of maximal levels of activity. Administration of the antiandrogen flutamide to intact rats caused a moderate decrease in epididymal weight, whereas this effect was more pronounced in castrated, androgen-treated rats. In the latter, the effect of flutamide was significant at the lowest dose used (0·5 mg/day). ODC activity was significantly decreased by flutamide treatment of intact rats, but even at the highest dose used (10 mg/day) only a 39% inhibition was observed. In flutamide-treated rats, LH concentrations were markedly increased, as were serum and epididymal androgens. In androgen-treated castrated rats, flutamide caused epididymal ODC to fall to undetectable values. These results show that: (1) androgens are essential for the maintenance of ODC activity in the epididymis; (2) epididymal ODC activity is maximally stimulated by endogenous androgens, at least in the pubertal rat; (3) the apparent potency of flutamide is substantially lowered by an increase in epididymal androgens. We suggest that ODC is a sensitive marker of the action of androgens and antiandrogens in the epididymis.
Keywords: androgen; antiandrogen; epididymis; ornithine decarboxylase; rat
María A. de Larminat, M. J. Hinrichsen, C. Scorticati, J. M. Ghirlanda, J. A. Blaquier and R. S. Calandra
Summary. Uptake and metabolism of [3H]testosterone, mainly to 5α-dihydrotestosterone (5α-DHT) and 5α-androstanediol were higher in the caput than in the cauda epididymidis in vitro. The metabolites represented 57, 49 and 47% of the total radioactivity in the caput, corpus and cauda epididymidis, respectively; subcellular distributions of the metabolites in each segment showed 67% of total radioactivity in cytosol and 18% in the nuclei. In both fractions, the amount of 5α-DHT was greater than that of androstanediol while the reverse was true for the mitochondria and microsomes.
The distribution of 5α-reductase activity in subcellular fractions was similar to that of the microsomal marker enzyme NADPH: cytochrome C reductase, whilst 3α-hydroxysteroid dehydrogenase was found mainly in the cytosol. Maximal 5α-reductase activity was at pH 5·3, apparent K m values in the microsomal and nuclear fractions were 1·65 ± 0·7 and 1·75 ± 0·36 × 10−6 m respectively, and the V max in these preparations was 5·28 ± 1·19 and 3·1 ± 0·52 pmol/mg protein/min, respectively. The activity of 5α-reductase was inhibited by Zn2+, Cu2+, Ba2+ and Cd2+ and by epitestosterone, progesterone and 4-androstene-3-one-17β-carboxylic acid.