M. Rajalakshmi

Pharmacokinetics and pharmacodynamics of a new long-acting androgen ester: maintenance of physiological androgen levels for 4 months after a single injection.

The pharmacokinetics and pharmacodynamics of testosterone trans-4-n-butylcyclohexyl carboxylate (Code name: 20 Aet-1), a new long-acting androgen ester, were evaluated in castrated adult rhesus monkeys and compared with those of testosterone enanthate (TE). A single intramuscular injection of 40 mg of 20 Aet-1 returned serum testosterone (T) to within or close to the diurnal physiological range for 80-136 days. In contrast, a similar dose of TE increased serum T to supraphysiological levels and the response evoked was of short duration. The ratio of T to dihydrotestosterone (T/DHT) ratio in monkeys treated with 20 Aet-1 was comparable to that found in control animals while in TE-treated animals, it was highly elevated. Serum estradiol (E2) elevation by 20 Aet-1 was also of smaller magnitude compared to TE. 20-Aet-1 suppressed LH levels from day 5 until day 115. The levels of LH on day 115 were 45.8% lower compared to the levels on day 13 post-castration. TE suppressed LH levels from day 1-7 post-injection. The values on day 7 were 76.6% lower compared to values on day 13 post-castration. Thus, TE-induced suppression of LH was of shorter duration, but of greater magnitude compared to the effect caused by 20 Aet-1. Similarly, FSH was suppressed for a longer duration (days 21-74) by 20 Aet-1 than by TE. The results indicate that the new testosterone ester has highly favourable pharmacokinetic properties and may prove to be the androgen of choice for supplementation therapy in contraceptive regimens.

Inhibition of spermatozoa maturation in rhesus monkey by cyproterone acetate

The morphology of spermatozoa from the initial segment, caput, corpus and cauda epididymides of normal and cyproterone acetate-treated animals was studied using light and scanning electron microscopy to understand the changes taking place during spermatozoa maturation. A progressive and significant decrease in the percentage of spermatozoa that retained the cytoplasmic droplet and a shift in its position from proximal end of the midpiece to its distal end were seen during epididymal transit; these events were inhibited in cyproterone acetate-treated animals. A large percentage of spermatozoa from the initial segment and the caput epididymides showed coiling of the spermatozoa tail which involved the midpiece, principal piece and the endpiece. The percentage of spermatozoa that showed the coiled tail decreased; a gradual straightening of the spermatozoa tail with less complex types of coiling was also seen during epididymal transit. Cyproterone acetate reversed these changes occurring during maturation. These results indicate that spermatozoa maturation in the rhesus monkey, occurring between the corpus and cauda epididymides, is an androgen-dependent event.

Seminal fructose in normal and infertile men

Fructose levels and fructolysis index in human semen were analysed to assess a correlation, if any, between the levels of this glycolysable sugar and sperm concentration. Semen was collected from normospermic men and men with azoospermia or oligospermia. Seminal fructose levels were elevated in men with obstructive azoospermia and in men who remained azoospermic following vasoepididy mostomy done to correct epididymal blockage. Men with sperm concentration of less than 20 million/ml pre-operatively or following vasoepididy mostomy, showed significantly high levels of fructose and lower fructolysis index. Fructose levels in normospermic infertile men, as well as in men with normal sperm counts (more than 20 million/ml), were similar to that in men of proven fertility.

Effects of testosterone buciclate on testicular and epididymal sperm functions in bonnet monkeys (Macaca radiata)

The effects of testosterone buciclate (TB), a long-acting androgen ester given i.m. at four sites (20 mg/site) on days 1 and 91 of the study period (360 days), on reproductive and hormonal parameters were evaluated in five adult male bonnet monkeys; untreated animals (n = 5) acted as controls to monitor seasonal changes in these parameters. In control animals, testicular volume remained unchanged throughout the study; sperm count, motility and gel penetrability decreased while the percentage of spermatozoa showing retention of cytoplasmic droplet and coiled tail increased in June-July (days 210-240), preceded by reduction in serum testosterone (T) levels on days 120-150 (March-April). The TB-treated animals showed reduced testicular volume (days 90-270), suppressed sperm motility and gel penetrability (days 45-240 except on day 120), decreased sperm count (days 75-270), and an increased percentage of spermatozoa showing retention of cytoplasmic droplet and coiled tail (days 45-240 except on day 120). Even though serum T levels remained elevated until day 300, these levels were within the physiological range. The changes induced by TB were reversible. The suppression of testicular and epididymal functions by TB indicates that this long-acting androgen may have the potentiality to induce and maintain reversible sterility, but further evaluation needs to be carried out to develop an appropriate dosage regimen that would prevent return to normal functions in order to develop this long-acting androgen as a hormonal male contraceptive.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of the ability of a new long-acting androgen ester to maintain accessory gland function in castrated rhesus monkey

The ability of 40 mg of milled suspension of a new long-acting androgen ester (20 Aet-1) to restore and maintain accessory gland function was compared with that of testosterone enanthate (TE) in castrated adult rhesus monkeys. Castration did not abolish the ejaculatory response since only two animals did not void semen in the postcastration period. A single intramuscular injection of 40 mg of these compounds stimulated accessory gland function at levels lower than in the pretreatment period. 20 Aet-1-induced stimulation of prostatic acid phosphatase activity never exceeded control levels unlike that induced by testosterone enanthate which caused hyperstimulation on day 21 of drug treatment. In terms of support of accessory gland function, 20 Aet-1 would appear to offer hope of being a successful androgen for supplementation therapy in male animals.

Effect of dihydrotestosterone on testicular and accessory gland function in male rhesus monkeys

Pituitary, testicular and accessory gland functions were assessed at intervals of 10-20 days in adult male rhesus monkeys given 10, 100 or 1000 micrograms dihydrotestosterone (DHT). Circulating levels of LH and testosterone were suppressed. Ejaculated spermatozoa showed morphological abnormalities and decrease in motility but sperm counts were unaffected. Seminal fructose was decreased in animals receiving DHT. Sexual behaviour was maintained in these animals.

Suppression of testicular and epididymal functions in a non-human primate (bonnet monkey) by combined administration of a gonadotropin-releasing hormone antagonist and testosterone buciclate.

The ability of a long-acting androgen, testosterone buciclate (TB), to induce suppression of testicular and epididymal sperm functions when given in combination with a potent GnRH antagonist (Antide) either on day 1 or 45 of Antide administration (days 1-90) as well as the ability of TB to maintain Antide-induced suppression of spermatogenesis were evaluated in adult bonnet monkeys. A group of untreated animals (group I) acted as controls. All animals given Antide and androgen simultaneously (group II) became azoospermic but at different times. When androgen administration was delayed 45 days after start of Antide treatment (group III), the mean sperm concentration remained in the normospermic range and only three animals became azoospermic. Antide given alone (group IV) induced azoospermia in three animals and oligospermia in the remaining animals; spermatogenesis recovered when Antide was withdrawn and TB was injected. In all Antide-treated animals (groups II-IV), non-motile spermatozoa or sperm with non-progressive motility and poor gel penetrability were seen in the ejaculate.

Effect of two new androgen esters on serum levels of testosterone in castrated rhesus monkey

The pharmacokinetics of two new androgen esters were tested in castrated male rhesus monkeys. A single injection of 40 mg of 20 Aet-2 (testosterone-trans-4-n-pentyl cyclohexyl carboxylate) increased serum testosterone to three times the castrate levels and was maintained nearly at this level until day 182. When given as four separate injections of 20 mg each, 20 Aet-2 increased serum testosterone within 24 hours and the peak levels were attained on day 2 (34.6 +/- 6.20 nmol/L) which was more than five times the levels obtained by 40 mg 20 Aet-2 given as a single injection. This was followed by a decrease in serum testosterone until day 98 when the levels were similar to that in animals given a single injection of 20 Aet-2. Administration of 40 mg of 3 Ad (testosterone-cis-3-(n-hexyl) cyclobutane carboxylate) given as a single injection increased serum testosterone levels to reach a peak level (47.4 +/- 4.64 nmol/L) on day 5 followed by a gradual decrease to castrate levels by day 70. The profile of serum testosterone in animals injected with 80 mg of 3 Ad as four separate injections was similar to that in animals given a single dose of 40 mg of 3 Ad. The data suggest a correlation between the bioavailability of the drug and the formulation of the vehicle. The possible effect of hydrolysis rate on pharmacokinetics of the drugs is discussed.

In vitro organ culture of rhesus monkey epididymal tubules

The caput and cauda epididymal tubules of rhesus monkey were cultured for 5 days using a simple organ culture system. The viability of the tubules in culture was established by assessing: (a) the histology of the epididymis; (b) motility and viability of spermatozoa; and (c) scanning electron microscopic morphology of spermatozoa before and at the end of culture. The efficacy of the culture was evaluated by introducing the antiandrogen, cyproterone acetate, into the culture medium. Cyproterone acetate caused degenerative changes in the histology of the epididymis and coiling of the epididymal spermatozoa which may be due to alterations in epididymal milieu.

Effects of levonorgestrel butanoate alone and in combination with testosterone buciclate on spermatogenesis in the bonnet monkey

The spermatogenic effects of levonorgestrel butanoate were studied in adult male bonnet monkeys when administered alone and in combination with testosterone buciclate. Levonorgestrel butanoate (0.25, 1.0 and 2.5 mg kg−1) given as two injections on days 0 and 60 (groups II, III, IV) resulted in thickening and folding of the basement membrane and disruption of cell associations in groups III and IV (on day 120). In group II, no apparent changes in testicular histology were observed. When these doses of levonorgestrel butanoate were combined with 40 mg of testosterone buciclate (groups V, VI, VII), maximum changes were seen in group VI in which all stages of spermatogenesis were absent on day 120 except for a small number of spermatogonia. The changes caused by lower dose (group V) and higher dose (group VII) of levonorgestrel butanoate were less prominent than in group VI. A significant decrease in the number of dark A (Ad) and B spermatogonia was observed in all groups except for Ad spermatogonia on day 120 in group V, B spermatogonia on day 60 in group IV and B spermatogonia on day 120 in group III. A significant decrease in pachytene spermatocytes was seen on day 120 in groups V only. Early spermatids showed a significant decrease only in groups V and VII on day 120 of treatment. Advanced spermatids were suppressed significantly in group IV on day 60 and in groups IV and V on day 120. These data indicate that levonorgestrel butanoate (1.0 mg kg−1) in combination with 40 mg of testosterone buciclate was the most effective treatment in suppressing spermatogenesis. The site of action of this combination regimen is at the level of renewing Ad spermatogonia.