Synthesis and biological activity of [D-Trp6] chicken luteinizing hormone-releasing hormone |
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Authors: | Robert P Millar Judy A King |
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Institution: | 1. Department of Chemical Pathology, University of Cape Town Medical School, Observatory 7925, Cape Town, Republic of South Africa;2. Groote Schuur Hospital, Observatory 7925, Cape Town, Republic of South Africa |
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Abstract: | An agonist of chicken hypothalamic luteinizing hormone-releasing hormone (cLH-RH). D-Trp6] cLH-RH, was synthesized and tested for luteinizing hormone (LH)-releasing activity using dispersed chicken anterior pituitary cells, as well as for binding to rat anterior pituitary membrane receptors. cLH-RH and mammalian LH-RH (mLH-RH) gave identical dose-response curves in stimulating chicken LH release ( and respectively) and similar estimates of potency. The D-Trp6] analogs of cLH-RH and mLH-RH stimulated LH release at lower doses ( and respectively) and were approximately 20-fold more potent. In contrast to the activity in the chicken bioassay, cLH-RH bound to rat anterior pituitary membrane receptors with a much lower affinity than did mLH-RH and had a relative potency of 2%. D-Trp6] cLH-RH was approximately 100-fold more potent than cLH-RH in the rat receptor assay while D-Trp6] mLH-RH was 28-fold more active than mLH-RH. These data demonstrate that substitution of Gly6 of LH-RH with D-Trp enhances the LH release from chicken pituitary cells to a similar extent to that observed in mammals, and indicate that the approaches used to produce active LH-RH analogs in mammals are likely to be applicable to birds. |
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Keywords: | Chicken LH-RH agonist LH-releasing activity Receptor binding activity |
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