1: Am J Hypertens. 2004 Jan;17(1):25-30. 

Enhanced heme oxygenase-mediated coronary vasodilation in Dahl salt-sensitive
hypertension.

Johnson RA, Teran FJ, Durante W, Peyton KJ, Johnson FK.

Department of Physiology, Tulane University Health Sciences Center, New Orleans,
Louisiana 70112, USA. RobertJ393@aol.com

BACKGROUND: Cardiovascular tissues express heme oxygenase (HO), which
metabolizes heme to form carbon monoxide (CO). Carbon monoxide promotes
relaxation of coronary vascular smooth muscle. Increased HO-1 expression
provides cardioprotection during certain pathologic conditions. On a high salt
(HS) diet Dahl salt-sensitive (DS) rats develop hypertension that is accompanied
by left ventricular hypertrophy, whereas Dahl salt-resistant rats (DR) do not.
This study tests the hypothesis that cardiac HO-1 expression is increased in DS
rats with salt-induced hypertension and provides cardioprotection by promoting
coronary vasodilation. METHODS: Male DS and DR rats were placed on a HS (8%
NaCl) or low salt (LS, 0.3% NaCl) diet for 4 weeks. Cardiac HO isoform
expression were determined by immunohistochemistry. Experiments used isolated
paced Langendorff-hearts perfused at a constant flow. Changes in coronary
perfusion pressure and left ventricular contractility (dP/dt(max)) were measured
in response to an inhibitor of HO, chromium mesoporphyrin (CrMP). RESULTS: With
respect to the LS group, DS rats on HS diet showed elevated mean arterial
pressure and increased heart weight. Coronary arterial HO-1 immunostaining was
enhanced in HS rats, but HO-2 staining was similar in both groups. In isolated
Langendorff-hearts the HO inhibitor CrMP increased coronary perfusion pressure
and calculated coronary resistance, and decreased left ventricular contractility
(dP/dt(max)) in both groups, but the response was exaggerated in HS rat hearts.
In the DR strain, HS diet did not augment CrMP responses and had no effect on
any of the parameters measured with respect to the LS diet. CONCLUSIONS: These
findings suggest that coronary HO-1 expression is increased to promote enhanced
coronary vasodilation in DS rats with salt-induced hypertension.

PMID: 14700508 [PubMed - indexed for MEDLINE]