Renal microvascular features of hypertension in Japan, Guatemala, and the United States.

The finding of benign arteriolar nephrosclerosis at autopsy usually implies the prior existence of essential hypertension. It was found in this study that minor degrees of incipient nephrosclerosis in young people can be shown to correlate with seemingly trivial blood pressure elevations. In this study, autopsy tissues were used to assess the magnitude of early nephrosclerosis in five population groupings. A comparison of males in Tokyo, Japan, Guatemala, and New Orleans, La (blacks and whites); and females in Tokyo revealed significant differences among these populations. Blacks exceeded whites in New Orleans in the magnitude of incipient nephrosclerosis in all 10-year age groups from 15 through 24 years to 45 through 54 years. Guatemalan males were, on average, less affected than New Orleans whites in all age groups. The data for all males (age range, 15 through 54 years) in Tokyo revealed little difference in nephrosclerosis from those in New Orleans whites. Blood pressure data were obtained from reports of cross-sectional surveys in these five populations. Blood pressure in males varied across age x race subgroups in close parallel with nephrosclerosis (r = .90), implying that variation in blood pressure among groups of subjects is strongly nephrosclerosis linked, even at very young ages; findings for Tokyo females were aberrant in this correlation. The results suggest that the lifelong progression toward the hypertensive state begins in childhood, and that these beginnings are measurably in the population averages of both nephrosclerosis and blood pressure elevations. Moreover, population differences in these two commensurate measures of the early precursors of hypertension were found to be well established by the ages of 15 through 24 years and were sustained at least into the ages of 45 through 54 years. The years of adolescence are here brought under suspicion of special importance in setting the lifelong course toward the hypertensive state.

Fatty acid composition of adipose tissue in humans: differences between subcutaneous sites.

We compared the fatty acid composition of adipose tissue from three different sites, one deep-seated site (perirenal) and two subcutaneous sites (abdominal and buttock), in 143 autopsied adult humans aged 24-61 y. The proportion of saturated fatty acids was highest in the perirenal adipose tissue and lowest in buttock adipose tissue. The proportions of monounsaturated fatty acids in the three sites were in the reverse order. Linoleic and linolenic acids were similar in the three adipose-tissue sites, an important finding for those concerned about the essential fatty acids, which are solely derived from the diet. The results clearly show that the fatty acid composition of the two subcutaneous fat depots differ significantly. We conclude that abdominal fat is more saturated than buttock fat.

Evidence for the failure of the Laplace law as a sole explanation for wall thickening of arteries in hypertensive and aging normotensive kidneys.

Nephrosclerosis, the morbid condition of the kidney that accompanies essential hypertension, is characterized by thickening of the walls of cortical arteries. According to the law of Laplace, the tension in the wall of an artery should be proportional to the product of pressure (P) times diameter (D). Thus, if wall thickness (T) is governed by wall tension, then it should be proportional to the same product: T = kPD, where k is a proportionality constant. A comparison of immersion-fixed kidneys in normotensives aged 75 to 90 years with those aged 19 to 34 years showed the magnitude of k to increase with age. The increase was 41% in vessels that were relatively close to the heart (outer diameter, 150 to 300 microns) and 30% at the more remote level (outer diameter, 80 to 140 microns). In perfusion-fixed specimens, k also increased with age, being 77% and 35% greater, respectively, for the comparison between normotensives in the two age groups. Normotensives were defined to be those with mean blood pressure less than 115 mm Hg. A similar result was found by defining normotension to be systolic pressure less than 140 mm Hg. Wall thickness was not proportional to pressure in hypertensive compared with normotensive subjects, but rather to a quadratic function that combined age and blood pressure taken together. The law of Laplace did not fully encompass the data that relate the thickening of renal arterial walls to hypertension or to aging in the absence of hypertension. The thickening with age is structurally a metaplasia that exchanges fibrotic intima in the elderly for muscular media in the young. The result was reproduced in perfusion- as well as immersion-fixed specimens and is therefore not distorted by postmortem collapse. The results favor the conclusion that arterial wall thickening in hypertensive and aging normotensive kidneys is sclerosis and not adaptive hypertrophy.(ABSTRACT TRUNCATED AT 250 WORDS)

Two variants of nephrosclerosis separately related to age and blood pressure.

Two variants of nephrosclerosis, roughly corresponding to the arterial and the arteriolar forms, have been examined in a series of autopsy kidneys by five observers using quantitative morphometry. These two variants are both marked by fibroplastic intimal thickening and medial wastage in the arteries, but one of these affects vessels of sizes that are closer to the heart, whereas the other affects sizes that are more remote from the source of arterial pressure. Both types of nephrosclerosis were found to increase with aging in subjects without hypertension. Each year of aging added 0.15 units of intimal thickening to the close vessels and 0.11 to the remote vessels. Each millimeter of mercury of elevated blood pressure was equivalent to 1 year of aging in the close and 2 years in the remote levels of the arterial tree. The four variables, age, blood pressure, remote level intimal thickness, and close level intimal thickness, were found to hold complex curvilinear interrelationships when examined by regression analysis. A dynamic model was suggested by the following findings: The earliest changes shown by young normotensives are in the close vessels, possibly because of the aging effect of the normal pulse wave. Later, the changes extend into the remote level, perhaps because the thickened intima is rigid and propagates the pulse wave abnormally far into the smallest arteries. Hypertension could then be viewed either as a cause for an exaggeration of this normal process or as a consequence of its extension into the remote level vessels where resistance to blood flow is greater or both. The objective morphometric method showed good agreement in the findings by independent observers and is considered to be suitable for epidemiologic studies of nephrosclerosis.