Autoregulation in hypertension: a review.
The hypothesis examined here is that autoregulation of peripheral flow is the dominant factor in initiating and maintaining the rise in peripheral resistance in hypertension. Vascular smooth muscle possesses myogenic activity, which is dependent upon wall tension and thus upon intravascular pressure, but the activity is modulated by metabolic factors which are flow-dependent. Autoregulation of flow by the microvessels is considered to be a reflection of the wider concept of autoregulation of tissue or cellular oxygen tension through the control of oxygen delivery and extraction in relation to oxygen consumption. Indirect evidence for the hypothesis, involving the measurement of oxygen delivery and consumption both in the whole body and in defined regions in various forms of hypertension, is discussed. Individual and species differences in the type of response of the microvessels to changes in oxygen tension and in the dependence/independence of oxygen consumption on flow may account for some of the discrepant observations. Specific criticisms of the hypothesis are discussed and it is concluded that the balance of indirect evidence supports the hypothesis. Lastly, if autoregulation is indeed involved in development of hypertension, it constitutes only a part of a complex pathogenic mechanism, whose major role is to maintain sodium and water balance in the body.
Ledingham
J M
JM
Medical Unit, London Hospital Medical College, UK.
D000818:Animals; D004285:Dogs; D006706:Homeostasis / Q000502:physiology*; D006973:Hypertension / Q000503:physiopathology*; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D051381:Rats; D014655:Vascular Resistance / Q000502:physiology