PREPUBERAL OVINE MAMMARY DEVELOPMENT IS UNAFFECTED BY OVARIECTOMY

Crossbred ewe lambs were used in a 2 X 2 X 2 factorial design to deter mine the effect of ovariectomy, age, and estrogen administration on pr epuberal mammary development. Intact (I, n = 20) and ovariectomized (O VX, n = 17) lambs were sacrificed at 6 and 13 wk of age after 1 wk of either estrogen 0.1 mg/kg BW/day, s.c.) or vehicle injections. Ovariec tomies were performed at 10 +/- 1 d of age. At sacrifice, one mammary gland was dissected into parenchymal and stromal fractions for biochem ical analyses. Parenchymal explants from the remaining gland were labe led with [H-3]thymidine for histoautoradiography. Neither ovariectomy nor estrogen treatment affected body weight, total gland weight, or pa renchymal weight (P > 0.05). However, means for each of these variable s increased between 6 and 13 wk (P < 0.01). Analysis of relative mamma ry growth showed significant positive deviations from isometry. Howeve r, no significant difference in parenchymal allometry was observed bet ween I and OVX groups. Exogenous estrogen stimulated an increase (P < 0.05) in epithelial cell labeling with [H-3]thymidine, but neither ova riectomy nor age at sacrifice had any effect (P > 0.2) on epithelial l abeling. These results demonstrate that prepuberal allometric mammary growth in the ewe lamb does not require the presence of the ovary. (C) Elsevier Science Inc. 1998.