Anterior pituitary content and in vitro secretion of heterogeneous isoforms of bovine luteinizing hormone : effects of endocrine milieu and in vivo progestin treatment /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1990.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | Luteinizing hormone (LH) exists as a family of variants that differ in carbohydrate content (which influences the charge heterogeneity of the hormone). Steroids have been implicated in altering the distribution of these isoforms, yet limited information exists regarding the profile of bovine LH (bLH) isoforms and the influence of steroids on the distribution. Therefore, this study was conducted to investigate: 1) the profile of bLH isoforms from two physiologically different models (yearling steers vs prepuberal heifers); 2) the effects of in vivo progestin treatment on the in vivo and in vitro release of bLH in cycling heifers and 3) the influence of in vivo progestin treatment on the bLH isoform profile in the non-perifused and the perifused hemipituitary and on isoforms released in vitro in response to luteinizing hormone releasing-hormone (LHRH). Yearling steers (n=5) and prepuberal heifers (n=7) were utilized to determine if gonadal steroids influence the distribution of isoforms of bLH. Separation of the variants of pituitary-derived bLH was achieved by chromatofocusing based on differences in the apparent isoelectric point (pi). Ten isoforms of bLH were detected in yearling steer pituitary homogenants, whereas, six isoforms were detected in prepuberal heifer pituitary homogenants. The predominant isoform for both yearling steers and prepuberal heifers eluted at an apparent pi of 8.89 (28% and 19% of total isoforms, respectively). Cycling heifers were sampled (15 min interval for 6 hr) to evaluate the effects of in vivo progestin (norgestomet) treatment on LH release. In vivo release of LH pre- or post-LHRH and during LHRH-induced (100 ug) LH release did not differ between heifers with the progestin implant in place (0 hr) or 24 hr post-implant removal (24 hr). However, during in vitro perifusion pituitary slices from the 24 hr group released more LH pre- and post-LHRH and during LHRH-induced LH release. Ten isoforms of bLH were detected both within the hemipituitaries that were not perifused (stored) and in hemipituitaries after-perifusion... |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Physiology of reproduction." |
| Physical Description: | xi, 112 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |