CAROTID-ARTERY MECHANICAL-PROPERTIES OF DAHL SALT-SENSITIVE RATS

We evaluated the mechanical properties of the carotid artery in anesth etized Dahl rats with or without long-term treatment with the diuretic compound indapamide. The mechanical properties of the carotid artery were evaluated by establishing pressure-volume curves in situ in vivo before and after total relaxation of arterial smooth muscle by potassi um cyanide. Dahl salt-sensitive and salt-resistant rats were fed eithe r a low (0.4%) or high (7%) NaCl diet for 5 weeks. In each group, half the rats received for the same period of time oral treatment with ind apamide (3 mg/kg per day). Blood pressure, heart rate, and pressure-vo lume curves were studied at the end of the 5-week period. In untreated Dahl salt-sensitive rats, the pressure-volume curve of the carotid ar tery was shifted to the right compared with that in untreated Dahl sal t-resistant rats. The finding was observed even after potassium cyanid e and regardless of the NaC1 diet (P<.01 between Dahl salt-sensitive a nd -resistant rats). Indapamide was able to prevent the development of hypertension in Dahl salt-sensitive rats receiving a high NaC1 diet ( 185+/-7 versus 146+/-8 mm Hg in untreated and treated Dahl salt-sensit ive rats with a high NaCl diet, P<.0005). In the other groups, indapam ide had no effect on blood pressure. Indapamide treatment increased ca rotid arterial static compliance in Dahl salt-sensitive rats with a hi gh or low NaCl diet and to a lesser extent in Dahl salt-resistant rats . The increase was observed even after total relaxation of carotid art erial smooth muscle by potassium cyanide. These results suggest that ( 1) the mechanical properties of the carotid arteries were altered in D ahl salt-sensitive rats independently of NaCl diet and transmural pres sure changes, and (2) the diuretic compound indapamide prevented the d isturbed mechanical properties of the carotid artery in Dahl salt-sens itive rats with a high or low NaCl diet, acting on both arterial struc ture and function. Sodium sensitivity (and not sodium intake) influenc es the changes in the carotid artery mechanical properties of Dahl rat s.