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(Hypertension. 2001;38:679.)
© 2001 American Heart Association, Inc.
Endocrine Systems |
From Department of Medicine, College of Human Medicine, Michigan State University, East Lansing.
Correspondence to Scott C. Supowit, PhD, Michigan State University, B-338 Clinical Center, East Lansing, MI 48824. E-mail scott.supowit{at}ht.msu.edu
Abstract
Abstract Calcitonin gene-related peptide (CGRP) and substance P are known to play a counterregulatory role in acquired models of salt-dependent hypertension. In contrast, neuronal production of these peptides is decreased in the spontaneously hypertensive rat, which may contribute to the elevated blood pressure. To determine the role played by CGRP and substance P in Dahl-salt hypertension, 4- to 6-week-old male salt-resistant (DR) and salt-sensitive (DS) rats were divided into 4 groups (n=5/group) and pair-fed low-salt (0.2% NaCl) (DR/LS and DS/LS) and high-salt (8% NaCl) diets (DR/HS and DS/HS) for 3 weeks. After 3 weeks, all the rats had venous (for drug administration) and arterial (for blood pressure monitoring) catheters surgically implanted and were studied in the conscious and unrestrained state. Mean arterial pressure was significantly higher in the DS/HS rats animals (185.8±1.6 mm Hg, P<0.001). Intravenous administration of CGRP and SP receptor antagonists was without effect in any of the groups studied. CGRP and SP mRNA content from dorsal root ganglia were not significantly different between the groups. Whereas immunoreactive CGRP was decreased in the DS groups (DS/HS, 9.4±0.4 pg/µg protein; DS/LS, 11.1±0.8 pg/µg protein; P<0.01) compared with the DR groups (DR/HS, 13.9±0.6 pg/µg protein; DR/LS, 14.6±0.6 pg/µg protein), neuronal SP production was similar between all the groups. Thus, CGRP and substance P do not play a counterregulatory role in Dahl-salt hypertension. The decrease in neuronal CGRP expression in DS rats appears to be genetically determined as in SHR, however, and may contribute to the increase in blood pressure following salt-loading.
Key Words: rats neuropeptides hypertension, genetic blood pressure RNA radioimmunoassay
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