The role of thymus graft on the onset of puberty in juvenile male rats

Abstract

There exists a bidirectional relation between the thymus gland and the hypothalamo- hypophysial-gonadal axis. The thymus secretes various hormones, some of which can regulate the reproductive axis. So, it is worth to explore the possible role of an additional thymus on the onset of puberty in male albino rats. Two groups of male rats aged 5 and 10 days were used for the study. Each subgroup consisted of 4 pups each in control and experimental group. Thymus glands for graft were obtained from newborn male rat pups. Depending on the age group, 5 day or 10-day-old male rat pup were anaesthetized, 2-3 mm incision was made, and a thymus gland was grafted to the axilla. Sham operations were performed to the control pups. Without handling, animals were observed daily for the onset of puberty. On the day of descent of testes, body weight of the animal was noted, blood was collected and used for radio immunoassay. All morphometric measurements were done using an occular micrometer. Volume fraction of seminiferous tubules, intertubular connective tissue of testes, cortex and medulla of the thymus were estimated by point count method. In both the age groups thymus graft advanced the age of descent of testes, and increased body weight and organ weight. It also increased the serum hormone levels. In conclusion, this study indicates that an additional thymus gland has a positive effect on the male reproductive system towards pro-gonadal action, and this effect is more pronounced in older-age groups of rats.