Abstract
Background:
The adrenal glands play a vital role in regulating endocrine functions by producing corticosteroids, mineralocorticoids, and androgens. Adrenal androgens contribute to overall systemic androgen levels, primarily through interactions with androgen receptors (AR) within the gland. Although the distribution of AR has been studied in various mammalian species, no research has yet focused on the Sunda porcupines (Hystrix javanica), a species of considerable ecological importance in Indonesia.

Aim:
This study aimed to investigate the endocrinal regulation of the adrenal gland of Sunda porcupines (Hystrix javanica) by examining the distribution of androgen receptor-immunoreactive (AR-IR) cells.

Methods:
This study was conducted at the Laboratory of Anatomy, Faculty of Veterinary Medicine, Universitas Gadjah Mada, Indonesia, from January to August 2022. The research involved six adrenal glands sourced from Sunda porcupines (H. javanica), without regard to sex or age. A sample size of six Sunda porcupines is acceptable for the initial descriptive analysis. Normal tissue specimens were collected and subsequently fixed in Bouin’s solution for 24 h. Tissues were then processed and embedded in paraffin blocks. Histological evaluation was performed in routine staining, and immunohistochemistry (IHC) was performed to detect AR expression. In the IHC procedure, a primary antibody against the androgen receptor, produced in rabbits and polyclonal in nature, which specifically binds to the activated form of the receptor, was used. The localization and distribution of AR-IR cells were assessed descriptively across different zones of the adrenal gland cortex, namely, the glomerulosa (ZG), fasciculata (ZF), and reticularis (ZR), including the medulla.

Results:
AR-IR cells were predominantly localized in the ZG, with a smaller presence observed in the ZF of the adrenal cortex. No AR expression was detected in the ZR. Interestingly, AR-IR cells were also detected in the adrenal medulla.

Conclusion:
This study indicates species-specific distribution patterns of AR-IR cells, which may clarify the role of ARs in physiological adaptation of Sunda porcupines (H. javanica).

Key words: Adrenal gland; Androgen receptor; Androgen receptor-immunoreactive cells; Adrenal androgen; Sunda porcupines.