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This Article Full Text Full Text (PDF) All Versions of this Article: 70/2/379    most recent biolreprod.103.020420v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal My Folders Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Sen, A. Articles by Flores, J. A. Search for Related Content PubMed PubMed Citation Articles by Sen, A. Articles by Flores, J. A. Agricola Articles by Sen, A. Articles by Flores, J. A.

Expression and Activation of Protein Kinase C Isozymes by Prostaglandin F₂ in the Early- and Mid-Luteal Phase Bovine Corpus Luteum¹

Department of Biology,³ Eberly College of Arts & Sciences, West Virginia University, Morgantown, West Virginia 26506 Division of Animal and Veterinary Science,⁴ Davis College of Agriculture, Forestry and Consumer Science, West Virginia University, Morgantown, West Virginia 26506

Western blotting was used to identify the array of protein kinase C (PKC) isozymes expressed in the early (Day 4) and midcycle (Day 10) bovine corpus luteum (CL). PCK, ßI, ßII, , and µ isozymes were detected in total protein samples prepared from both Day-4 and Day-10 corpora lutea. In contrast, specific antibodies for PKC, , , and isozymes failed to detect protein bands in the luteal samples. PKCßII and isozymes were expressed differentially at these two developmental stages of the bovine CL. In the Day-4 luteal samples, PKC was barely detectable; in contrast, in the Day-10 samples, the actin-corrected ratio for PKC was 1.16 ± 0.13. This ratio was higher than the detected ratio for PKCßI and µ at this developmental phase of the CL (P < 0.01), but it was comparable with the ratio detected for the PCK and ßII. The amount of PKCßII was, although not as dramatic, also greater in the Day-10 CL (actin-corrected ratio was 0.85 ± 0.2) than in the Day-4 CL (0.35 ± 0.09 [P < 0.01]). The actin-corrected ratios for all other PKC isozymes, (Day 4 = 0.93 ± 0.16, Day 10 = 0.97 ± 0.09), ßI (Day 4 = 0.54 ± 0.073, Day 10 = 0.48 ± 0.74), and µ (Day 4 = 0.21 ± 0.042, Day 10 = 0.21 ± 0.38) were not different at these 2 days of the cycle. An experiment was designed to test whether activation of specific isozymes differed between CL that do or do not regress in response to PGF₂. Bovine CL from Day 4 and Day 10 of the estrous cycle were collected and 1 mm CL fragments were treated in vitro for 0, 2.5, 5, 10 or 20 min with PGF₂ (0.1, 1.0, and 10 nM) or minimal essential medium-Hepes vehicle. Translocation of PKC from cytoplasm to membrane fraction was used as indication of PKC activation by PGF₂. Evidence for PKC activation was observed in both Day-4 and Day-10 luteal samples treated with 10 nM PGF₂. Therefore, if PKC, an intracellular mediator associated with the luteal PGF₂ receptor, contributes to the lesser sensitivity of the Day-4 CL, it is likely due to the differential expression of the and ßII isozymes of PKC at this stage and not due to an inability of the PGF₂ receptor to activate the isozymes expressed in the early CL.

¹ This work was supported in part by a Senate Grant of the West Virginia University to J.A.F., USDA/CREES award 98-3503-6634 to J.A.F., and Hatch 321 (NE 161) award to E.K.I.

² Correspondence: Jorge A. Flores, Department of Biology, West Virginia University, 53 Campus Drive, Suite 3139, P.O. Box 6057, Morgantown, WV 26506-6057. FAX: 304 293-6363; jflores{at}wvu.edu

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