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thomas Gast; Retinal Arterioles Adapt to Systemic Hypertension by Maintaining Constant Tension in the Smooth Muscle Cells of the Arteriole Wall. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4049.
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© ARVO (1962-2015); The Authors (2016-present)
To understand the biological principles of vascular remodelling in the retinal arteriole wall that results in a thicker wall with a smaller lumen in primary systemic hypertension.
AOSLO data on the internal and external diameters of retinal arterioles from 55 subjects was classified into groups with low tension, normotension, and essential hypertension (HTN). These arterioles varied in size from the capillary level to over 150 microns in diameter. This data was analysed using LaPlace's law as well as collapsible tube theory.
The data relating vessel ID to OD for the 3 groups was of very high quality with R^2 ranging from 0.975 for the HTN subjects to 0.992 for the low tension subjects. Application of LaPlace's law showed that the, presumed to be unaltered by hypertension, walls of the low tension subjects have equal tension per unit wall thickness independent of the vessel diameter. Additionally, calculations on the walls of the normotensive and hypertensive subjects shows that the tension per unit wall thickness remains constant essentially identical to the tension present per unit wall thickness in the low tension subjects. This would seem to indicate that the fundamental regulatory mechanism utilized by the vascular system is maintaining constant tension in each cross sectional area of the vascular wall throughout life. It is also shown that under collapsible tube theory the retinal vascular branches will all collapse at the same external applied pressure.Substitution of experimental values into the formulas give collapse pressures similar to those seen experimentally.
Data on 3 classes of subjects with respect to systemic blood pressure shows thickening of arteriolar walls in HTN as shown by other researchers but low tension patients showed low variance linear data that may represent an initial state of the vasculature unmodified by the influence of elevated blood pressure.LaPlace’s law shows that the arterioles in LTN have equal tension per unit of wall thickness across all vessel diameters. Analysis of the walls in normotension and in HTN show that the tension per unit wall thickness is the same as that in the LTN case indicating that maintaining constant tension within the smooth muscle cells of the wall may be the fundamental physiological process at work in increasing vascular resistance in the presence of HTN.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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