Increased Angiotensin-(1–7) in Hypophysial-Portal Plasma of Conscious Sheep
| Autor: | Iain J. Clark, Duncan J. Campbell, Anne C. Lawrence |
|---|---|
| Rok vydání: | 1992 |
| Předmět: |
medicine.medical_specialty
Endocrinology Diabetes and Metabolism Angiotensin III Angiotensinogen Radioimmunoassay Peptide hormone Gonadotropin-Releasing Hormone Cellular and Molecular Neuroscience Endocrinology Prolyl endopeptidase Internal medicine Endopeptidases Renin Renin–angiotensin system Animals Medicine Chromatography High Pressure Liquid Sheep Endocrine and Autonomic Systems business.industry Angiotensin II Serine Endopeptidases Median Eminence Hypophyseal portal system Peptide Fragments Portal System Hypothalamus Pituitary Gland Median eminence Angiotensin I Peptides Prolyl Oligopeptidases business medicine.drug |
| Zdroj: | Neuroendocrinology. 55:105-114 |
| ISSN: | 1423-0194 0028-3835 |
| DOI: | 10.1159/000126103 |
| Popis: | Studies were undertaken to characterize angiotensin peptides in hypophysial-portal blood of conscious sheep and to determine whether the median eminence (ME) secretes angiotensin peptides into the hypophysial-portal circulation. Simultaneous measurements of angiotensin peptides in jugular and hypophysial-portal plasma were performed in 6 sheep. Cerebrospinal fluid (CSF) was collected and data for hypophysial-portal plasma were corrected for CSF contamination. Angiotensin peptides were also measured in extracts of sheep ME. In a separate group of 4 sheep, simultaneous measurements of angiotensin peptides in arterial and jugular plasma were performed. Using high performance liquid chromatography-based radioimmunoassays, 8 angiotensin peptides were measured: Ang-(1-7), Ang II, Ang-(1-9), Ang I, Ang-(2-7), Ang III, Ang-(2-9), and Ang-(2-10). Renin, angiotensinogen and prolyl endopeptidase were also measured. No differences in angiotensin peptide levels in arterial and jugular plasma were observed. Angiotensin peptide levels in hypophysial-portal plasma were similar to those in jugular plasma, except for Ang-(1-7), the levels of which were 5-fold higher in hypophysial-portal plasma, and Ang I, for which the levels in hypophysial-portal plasma were 46% of the jugular levels. Renin and angiotensinogen levels were similar in arterial, jugular, and hypophysial-portal plasma. Angiotensin peptide contents of sheep ME were less than 16 fmol/ME. However, the prolyl endopeptidase content of sheep ME was 430-fold higher than plasma levels. The low levels of angiotensin peptides in sheep ME indicate that it does not secrete these peptides into the hypophysial-portal circulation. Rather, the high level of prolyl endopeptidase in ME is consistent with region-specific metabolism of Ang I delivered to the ME by arterial blood, generating increased levels of Ang-(1-7) in hypophysial portal plasma. The increased levels of Ang-(1-7) in hypophysial-portal plasma may play a role in regulation of pituitary function. |
| Databáze: | OpenAIRE |
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