In Memoriam |
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Authors: | TS Gross WF Williams CS Galina J Manspeaker MA Haaland E Russek |
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Institution: | 1. Animal Sciences Department, University of Maryland, College Park, MD 20742 USA;2. National University of Mexico, Ciudad Universitaria, Villa Obregon Mexico;3. Virginia-Maryland Regional College of Veterinary Medicine, Maryland Campus, College Park, MD 20742 USA |
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Abstract: | Thirteen cows, Experiment I, were injected at 1 h post-partum with saline (n=4) or Human Chorionic Gonadotropin, (HCG) (n=9). Eleven additional cows, Experiment II, were ovariectomized (ovx) unilaterally at 10 days pre-partum (n=4) or 4 h post-partum (n=7) to remove the only corpus luteum (CL). These ovx post-partum animals (n=7) were also injected as part of Experiment I with saline (n=2) or HCG (n=5). All CL were sliced and incubated in media alone and with LH, tritium-labeled-pregnenolone (3HP5) or both. Blood samples were collected pre- and post-injection, Experiment I and pre- and post-surgery, Experiment II. Plasma and media samples were analyzed for progesterone (P4) by radioimmunoassay. Media samples with 3HP5 were chromatographed for determination of P5 conversion to P4. No significant differences (P > 0.1) between P4 profiles for saline or HCG treated animals were observed. Pre- and post-partum CL slices were able to convert P5 to P4. Post-partum CL slices were unresponsive to LH whereas pre-partum slices responded. These data indicate the decline in luteal function peri-partum is probably not due to withdrawal of gonadotropin support. |
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