Increased Angiotensin-(1–7) in Hypophysial-Portal Plasma of Conscious Sheep
作者:
Anne C. Lawrence,
Iain J. Clark,
Duncan J. Campbell,
期刊:
Neuroendocrinology
(Karger Available online 1992)
卷期:
Volume 55,
issue 1
页码: 105-114
ISSN:0028-3835
年代: 1992
DOI:10.1159/000126103
出版商: S. Karger AG
关键词: Angiotensin I;Angiotensin II;Angiotensin III;Angiotensin-(1-9);Angiotensin-(2-7);Angiotensin-(2-9);Angiotensin-(2-10);Median eminence;Prolyl endopeptidase
数据来源: Karger
摘要:
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 < 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 pitui
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