Changes in the Pituitary‐interrenal Axis after Gonadectomy in the Catfish, Clarias batrachus (Linn.)

The effects of gonadectomy on the cytological structure of the hypophysis and interrenal tissue of Clarias batrachus have been investigated. Forty days after gonadectomy remarkable hypertrophy of certain cyanophils, identified later as gonadotrops, has been observed followed by hyperplasia. The somatotrops also seem to undergo similar changes, and as a result the proximal pars distalis (PPD) increases enormously and encroaches upon the pars intermedia (PI). The gonadotrops undergo a gradual degranulation and become devoid of stainable cytoplasm by 90 days. No signet ring cells have been noticed at any stage. The cyanophils in the ventral region of the PPD, identified as thyrotrops, also show degranulation, but to a comparatively limited degree. The ACTH cells undergo gradual hypertrophy and degranulation. A progressive increase is noticed in the nuclear diameter. The interrenal cells are activated as indicated by the enhanced nuclear indices. It is suggested that a fall in gonadal steroids may result in ACTH release which in turn activates the interrenal cells.