Low birth weight-associated adult hypertension in the rat
Epidemiological surveys have suggested that intrauterine growth retardation is a risk factor for the development of hypertension in later life. A rat model of intrauterine growth retardation, induced by maternal low-protein diet during the second half of pregnancy, was used to study the relationship between birth weight and adult hypertension. The offspring were born at term and were allowed to nurse normally until weaned to standard chow at 4 weeks of age. They had 15% lower birth weights than control offspring, with complete catch-up growth by age 4 weeks. Both females and males developed progressively worsening hypertension beginning at 8 weeks. The 11-month survival rate was 69% versus 100% in control animals. During the early stages of the hypertension, plasma creatinine was normal, plasma sodium concentration was slightly higher than that of control animals, plasma renin activity was suppressed, and the males had mild proteinuria. Renal function remained normal throughout the 11-month observation period, but plasma renin activity gradually rose above control values. Angiotensin-converting enzyme inhibition by enalapril, begun at 8 weeks of age, was effective in completely normalizing the blood pressure, but did not totally prevent the extra mortality. Sprague- Dawley and Wistar rat strains developed equally severe hypertension after maternal protein deprivation, despite their different susceptibilities to nephrosclerosis with aging. In conclusion, maternal low-protein diet resulted in low birth weight and adult hypertension in the rat. Primary sodium retention and expanded extracellular volume may be critical factors during the development of the hypertension.
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