The effect of testosteron on Ascaris suum worm load and larval growth were studied. The results revealed that the effect of testosterone on A. suum infection was dose dependent. Administration of 0.5 mg testosterone propionate (TP) for 18 days significantly increased the mice susceptibility to A. suum infection (66.2 ± 11.15 larvae) (mean ± S.E.) when compared to the control. Higher dosage of testosterone (1.0, 2.5 or 5.0 mg TP) did not show any significant effect. The present experiment also showed that administration of testosterone (0.5 mg TP) for 7 days increased the host susceptibility (86.1 ± 5.86 larvae) to A. suum infection compared to the control (14.6 ± 1.71 larvae) (P < 0.001). Similar results were found when the hormone was administered for 14 and 28 days. On the contrary, when gonadectomised mice were given 0.5 mg TP, the level of susceptibility increased (P < 0.001). It is believed that testosterone indirectly influence the parasitic infection through its effect on the lymphoid organs.
Kesan testosteron terhadap bebanan dan pertumbuhan larva Ascaris suum telah dikaji. Hasil kajian menunjukkan bahawa pengaruh testosteron terhadap infeksi A. suum adalah bergantung kepada takaran hormon yang diberikan. Didapati hanya takaran 0.5 mg testosteron propionat (TP) yang diberikan selama 18 hari meninggikan kerentanan mencit (66.2 ± 11.15 larva) (min ± S.E.) terhadap infeksi parasit jika dibandingkan dengan kawalan (38.0 ± 7.13 larva) (P>0.05). Takaran testosteron yang lebih tinggi (1.0, 2.5 atau 5.0 mg TP) tidak menunjukkan kesan yang jelas. Hasil percubaan juga menunjukkan bahawa pemberian hormon (0.5 mg TP) selama 7 hari boleh meningkatkan kerentanan perumah (86.1 ± 5.86 larva) terhadap infeksi A. Summ. Perbandingan dengan kawalan (14.6 ± 1.71 larva) dan menunjukkan perbezaan yang nyata pada P < 0.001. Begitujuga dengan pemberian hormon selama 14 dan 28 hari. Sebaliknya gonadektomi telah mengurangkan kerentanan mencit terhadap infeksi A. suum. Walau bagaimanapun, kesan sebaliknya didapati apabila mencit yang gonadektomi itu diberi suntikan 0.5 mg TP (P < 0.001). Hormon testosteron dipercayai mempengaruhi corak infeksi parasit secara tidak langsung dengan mempengaruhi perkembangan organ-organ limfoid.
Gonadectomized male mice aged 5 weeks were given 5 mg testosterone propionate daily for 14 days. The treatment significantly decreased the number of blood leukocytes. The number of all individual types of leukocytes except basophils in vehicle-treated gonadectomized mice was increased. Testosterone-treated mice consistently had a lower number of leukocytes after being infected with Plasmodium berghei than did vehicle-treated mice. The results suggest that testosterone suppresses the production of leukocytes and that testosterone-treated mice become more susceptible to parasite infection.
Gonadectomized male albino rats aged 7 weeks were given 1.5 mg/kg testosterone propionate daily and inoculated with 50 third-stage larvae of Angiostrongylus malaysiensis. The treatment significantly increased the number of larvae and adult worms recovered from the brain and pulmonary arteries, respectively, and the rats exhibited smaller thymus glands. The total numbers of leukocytes, monocytes, neutrophils, and especially eosinophils increased significantly post-infection, but the counts were higher in the untreated infected controls. Presumably, immunosuppressive effects of testosterone may at least partly be responsible for the higher loads of A. malaysiensis worms found in male rats as compared with females in the field.
Daily intramuscular injection with thyroxine (T4) at a dose of 2.5 micrograms/100 g body weight decreased the larvae and adult worm burden of Parastrongylus malaysiensis in the brain and pulmonary arteries of male Sprague-Dawley albino rats. In contrast, rats treated with propyl thiouracil (PTU), an antithyroid drug, at a dose of 3.75 mg/100 g body weight retained greater numbers of larvae and adult worms. The results may reflect the contrasting immunomodulatory effects of T4 and PTU that influence the susceptibility of the host.
Gonadectomized male laboratory rats were given 0.06 mg/kg estradiol benzoate daily for 14 days before being inoculated with 50 third-stage larvae of Parastrongylus malaysiensis. Hormone treatment was continued until the rats were killed. The numbers of larvae in the brain and of adult worms in the pulmonary area of the rats were determined every 7 days after the inoculation. It was found that the rats treated daily with estradiol benzoate had significantly and consistently higher numbers of larvae and adult worms as compared with the controls. The number of total leukocytes increased significantly after the rats were infected. The results show that estradiol-treated rats become susceptible to P. malaysiensis infection, which may indicate that the immunosuppressive effects of testosterone observed in earlier studies may partly be caused by estradiol that was peripherally aromatized from testosterone.