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Title: EFFECT OF ZERANOL ON TRANSCRIPTIONAL REGULATION OF PITUITARY SYNTHESIS AND SECRETION OF GROWTH HORMONE IN GROWING WETHER LAMBS

Author
item THOMAS, M - UNIVERSITY OF MISSOURI
item RAYMOND, S - UNIVERSITY OF MISSOURI
item Carroll, Jeffery - Jeff Carroll
item Matteri, Robert
item HILLMAN, L - UNIVERSITY OF MISSOURI
item CHANETSA, F - UNIVERSITY OF MISSOURI
item ROZEBOOM, K - UNIVERSITY OF MISSOURI
item LIPSEY, R - UNIVERSITY OF MISSOURI
item KEISLER, D - UNIVERSITY OF MISSOURI

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 8/1/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The DNA binding protein, Pit-1, is a regulator of the growth hormone (GH) and prolactin genes. In rodents, Pit-1 interacts with the estrogen- estrogen receptor complex to transactivate the prolactin gene. Since estrogens increase pituitary secretion of GH in ruminants, we hypothesized that estrogen and Pit-1 would interact to enhance pituitary synthesis and secretion of GH. To test this hypothesis, 66 crossbred wethers (< 2 wk of age) were assigned by breed-type to either a control (CT) or one of three groups implanted with the estrogenic growth promotant, zeranol (Z, 12 mg, Ralgro, Mallinckrodt Vet). Implant groups were: Z0 (implanted d0, d45, and d90), Z45 (implanted d45 and d90), and Z90 (implanted d90). Twenty- eight d after implant, serum was collected every 12 min for 4 h prior to pituitary collection from a subset of wethers from CT and Z groups (n < 4 per group). Pituitary mRNA levels of GH and Pit-1 were determined with RNA Aslot blot analyses and densitometry. Spearmans correlation of the relationship of these factors to serum concentrations of GH, pituitary weight, and treatment are as follows (* = r P < .05): Pituitary weight Treatment GH mRNA Pit-1 mRNA -.11 .37* .40* -.10 Serum GH .36* .57* .44* Pituitary weight .08 .10 Treatment .31* GH mRNA These data do not provide evidence to support the hypothesis that estrogen stimulates pituitary secretion of GH in ruminants through an interaction involving Pit-1.