| Summary: | The present study reports the effects of MMI-treatment and castration on the maturation of the pituitary of White Leghorn cockerels. Body weights increase with age, but are significantly lower in the MMI-treated birds. Increases in total serum proteins and albumin in MMI-treated birds results in a much higher albumin/globulin ratio than that found in other birds. Castrated birds have the heaviest and MMI-treated birds have the smallest pituitaries. The increase in pituitary size appears to be due to cellular hypertrophy since the amount of DNA/gland is the same in castrated and control birds and is less in MMI-treated birds. Serum GH, TSH, T₃, and T₄ decreased with age in all groups, but were lowest in MMI-treated cockerels. Serum LH levels were highest in castrated birds and lowest in MMI-treated birds and serum prolactin highest in MMI-treated birds. Thyrotrophs, corticotrophs and lactotrophs were restricted to the cephalic lobe and somatotrophs occurred only in the caudal lobe. Luteotrophs occurred in both cephalic and caudal lobes of the pituitary. An increase in TSH, GH, PRL, ACTH, and LH cells occurred during maturation in both control and castrated birds but PRL, TSH and LH producing cells decreased in MMI-treated birds. Somatotrophs decreased in size with age as did their granules. Castrated birds had gonadotrophs that were significantly larger than those of normal or MMI-treated birds. This increase in gonadotroph size made a significant contribution to the postnatal increase in the size of the pituitary gland.
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