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ARS Home » Research » Publications at this Location » Publication #91993
Title: INFLUENCE OF CONTINUOUS GROWTH HORMONE ADMINISTRATION IN ADULT FEMALE CHICKENS

Author
item SCANES, COLIN - RUTGERS UNIVERSITY
item Proudman, John
item RADECKI, STEVEN - RUTGERS UNIVERSITY

Submitted to: General and Comparative Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Sulfamethazine (SMZ) has been shown to advance sexual maturation in broiler male chicks. It results in a transient reduction in plasma thyroid hormone T3 and a significant elevation of luteinizing hormone. The purpose of this study was to determine whether or not changes in gonadotrophs (LH-cells) and thyrotrophs (TSH-cells) could be detected in the anterior pituitary following dietary administration of SMZ. Male broiler chicks were fed a standard broiler ration from hatch until one week of age; experimental chicks were then switched to either an SMZ or control diet. At 1, 2, 3, and 7 days following intake of experimental diets, 3 chicks were sampled from each group, anesthetized, and perfused with heparinized saline followed by 4% paraformaldehyde. Brains were then blocked in sagittal plane and the mid-portion of brain with pituitary intact was dissected, dehydrated and embedded in paraplast. Sections were cut at 8 m and prepared for immunocytochemistry. Polyclonal antibodies against chicken LH and asynthetic peptide of the C-terminal portion of chicken thyroid-stimulating hormone (TSH) were used. Thyrotrophs were found in the rostral lobe of the anterior pituitary with cells more densely immunostained in the ventral region. A significantly higher number of thyrotrophs were found in pituitaries of chicks which consumed SMZ for two days. Pituicytes immunostained for LH were found scattered throughout all regions of the anterior pituitary gland including pars tuberalis. A significantly greater number of LH cells were found in both the ventral and dorsal regions of the rostral lobe of SMZ-treated chicks on day seven following treatment. Results suggest that SMZ effects a transient peripheral reduction in T3 with a concomitant increase in pituitary TSH- and LH-cells.

Technical Abstract: A series of studies were conducted to determine whether growth hormone (GH) exerts effects on adult female chickens. Recombinant chicken GH was administered continuously via osmotic mini-pumps. No consistent effects of GH treatment were observed on reproductive indices. Hens receiving GH treatment for 10 days exhibited hepatomegaly and showed a tendency (P<0.1) for increased spleen and thymus weights. Moreover, there were increases i the circulating concentrations of insulin-like growth factor-I (IGF-I) and IGF-binding proteins (IGF-BPs) (22 kDa IGF-BP after 2, 5, and 10 days and 36 kDa IGF-BP after 10 days). To determine whether the changes in IGF-BPs were due directly to GH or indirectly via IGF-I, the effects of GH or IGF-I (recombinant human) treatment were compared. While GH again elevated the circulating levels of 28 and 36 kDa IGF-BPs, no such effect was observed with IGF-I treatment. However, both treatments exerted similar effects in depressing pituitary GH mRNA levels and elevating plasma concentrations of IGF-I. It is concluded that GH directly elevates circulating concentrations of IGF-I and IGF-BPs, but the negative feedback on GH synthesis is mediated via IGF-I.