Carbon monoxide enhances development of hypertension in Dahl rats

The influence of carbon monoxide (CO) on the development of systemic hypertension was studied in Dahl rats selectively bred for susceptibility (DS) and resistance (DR) to NaCl-induced hypertension. This study was designed to examine the interactions among rat line (DS or DR), NaCl content of diet, and exposure to CO. The rats were exposed to 500 ppm CO or conditioned air, 21 hr/day, for 62 to 63 consecutive days. Carbon monoxide exposures affected blood pressure only in DS rats fed a high NaCl diet, where it enhanced the development of NaCl-induced hypertension. Whole-body weights were not affected by CO, but organ weight changes in the form of cardiomegaly ranging from 22% (DR, low NaCl) to 36% (DS, high NaCl), and splenomegaly ranging from 29% (DR, low NaCl) to 98% (DS, high NaCl) were observed. The mean equilibrium carboxyhemoglobin concentration was 42% in the CO-exposed rats. The hematologic responses to the CO exposures were elevated total hemoglobin and hematocrit.