RESUMO
Multiple cell membrane alterations have been reported to be the cause of various forms of hypertension. The present study focuses on the lipid portion of the membranes, characterizing the microviscosity of membranes reconstituted with lipids extracted from the aorta and mesenteric arteries of spontaneously hypertensive (SHR) and normotensive control rat strains (WKY and NWR). Membrane-incorporated phospholipid spin labels were used to monitor the bilayer structure at different depths. The packing of lipids extracted from both aorta and mesenteric arteries of normotensive and hypertensive rats was similar. Lipid extract analysis showed similar phospholipid composition for all membranes. However, cholesterol content was lower in SHR arteries than in normotensive animal arteries. These findings contrast with the fact that the SHR aorta is hyporeactive while the SHR mesenteric artery is hyperreactive to vasopressor agents when compared to the vessels of normotensive animal strains. Hence, factors other than microviscosity of bulk lipids contribute to the vascular smooth muscle reactivity and hypertension of SHR. The excess cholesterol in the arteries of normotensive animal strains apparently is not dissolved in bulk lipids and is not directly related to vascular reactivity since it is present in both the aorta and mesenteric arteries. The lower cholesterol concentrations in SHR arteries may in fact result from metabolic differences due to the hypertensive state or to genes that co-segregate with those that determine hypertension during the process of strain selection.
Assuntos
Animais , Masculino , Ratos , Aorta/química , Membrana Celular/química , Colesterol/análise , Hipertensão/metabolismo , Artérias Mesentéricas/química , Fosfolipídeos/análise , Colesterol/química , Espectroscopia de Ressonância de Spin Eletrônica , Cromatografia Gasosa-Espectrometria de Massas , Hipertensão/etiologia , Músculo Liso Vascular/química , Músculo Liso Vascular/citologia , Fosfolipídeos/química , Ratos Endogâmicos SHR , Ratos Endogâmicos WKYRESUMO
Multiple cell membrane alterations have been reported to be the cause of various forms of hypertension. The present study focuses on the lipid portion of the membranes, characterizing the microviscosity of membranes reconstituted with lipids extracted from the aorta and mesenteric arteries of spontaneously hypertensive (SHR) and normotensive control rat strains (WKY and NWR). Membrane-incorporated phospholipid spin labels were used to monitor the bilayer structure at different depths. The packing of lipids extracted from both aorta and mesenteric arteries of normotensive and hypertensive rats was similar. Lipid extract analysis showed similar phospholipid composition for all membranes. However, cholesterol content was lower in SHR arteries than in normotensive animal arteries. These findings contrast with the fact that the SHR aorta is hyporeactive while the SHR mesenteric artery is hyperreactive to vasopressor agents when compared to the vessels of normotensive animal strains. Hence, factors other than microviscosity of bulk lipids contribute to the vascular smooth muscle reactivity and hypertension of SHR. The excess cholesterol in the arteries of normotensive animal strains apparently is not dissolved in bulk lipids and is not directly related to vascular reactivity since it is present in both the aorta and mesenteric arteries. The lower cholesterol concentrations in SHR arteries may in fact result from metabolic differences due to the hypertensive state or to genes that co-segregate with those that determine hypertension during the process of strain selection.
Assuntos
Aorta/química , Membrana Celular/química , Colesterol/análise , Hipertensão/metabolismo , Artérias Mesentéricas/química , Fosfolipídeos/análise , Animais , Colesterol/química , Espectroscopia de Ressonância de Spin Eletrônica , Cromatografia Gasosa-Espectrometria de Massas , Hipertensão/etiologia , Masculino , Músculo Liso Vascular/química , Músculo Liso Vascular/citologia , Fosfolipídeos/química , Ratos , Ratos Endogâmicos SHR , Ratos Endogâmicos WKYRESUMO
Intravenous infusion of the converting-enzyme (CE) inhibitor, MK422 (1 mg X kg-1 X hr-1 for 30 minutes) in normotensive controls and two-kidney, one clip (2K1C) rats in the acute phase of renovascular hypertension had a significant hypotensive effect that persisted after 24 hours. In contrast to that prolonged effect, inhibition of the pressor responses to intraarterial or intravenous angiotensin I, and the potentiation of the depressor responses to intravenous bradykinin (BK), were evident during the hour following the infusion of MK422, but not 24 hours later. Potentiation of intraarterially administered BK, however, persisted for 24 hours after infusion of the CE inhibitor. It is concluded that at least the prolonged (24-hour) effect of the treatment with MK422 was due to inhibition of the CE activity in tissues other than the lung, and that increased levels of endogenous BK may be responsible for the inhibitor's hypotensive effect.
