Long-term effects of captopril on cellular sodium content and mechanical properties of aortic smooth muscle from spontaneously hypertensive rats.
The long-term effects of captopril on passive Na permeability and Na content in aortic smooth muscles of spontaneously hypertensive rats (SHR) were examined in relation to the mechanical properties of the muscles. Captopril or hydralazine when administered for 6 weeks exhibited antihypertensive action throughout the period. Cellular Na in both freshly excised aortas and incubated aortas from SHR leaked out more rapidly in cold Li-solution than those from normotensive Wistar-Kyoto rats, suggesting increased permeability in SHR aortas. Long-term treatment with captopril decreased the "permeability" of the vascular membrane of SHR, whereas hydralazine failed to decrease it. Incubation of the aortas in K+-free Tyrode's solution produced a slowly developing contraction. The rate of rise of this contraction was faster in SHR aorta that in Wistar-Kyoto aorta. In aortas from captopril-treated SHR, the rate of rise in the contraction was suppressed. The contractile response to K+-free medium was related to the passive permeability to Na and thereby to the increment of cellular Na. It is suggested that, after prolonged administration, captopril alters the abnormal permeability to Na of the vascular smooth muscle membrane in SHR and that the alteration contributes to the antihypertensive effect of the agent.
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002216:Captopril / Q000494:pharmacology*; D006830:Hydralazine / Q000494:pharmacology; D006973:Hypertension / Q000378:metabolism / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D011392:Proline / Q000031:analogs & derivatives*; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*; D014661:Vasoconstriction / Q000187:drug effects
D006830:Hydralazine; D011392:Proline; D002216:Captopril; D012964:Sodium