Aldosterone, Deoxycorticosterone, Corticosterone, and Prolactin Changes during the Lifespan of Chronically and Spontaneously Hypertensive Rats*

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Abstract
Male and female spontaneously hypertensive rats (SHR), which develop hypertension spontaneously with maturation, were autopsied at select time intervals from weaning to 28 months. Their blood pressure began to rise steeply at 4–5 weeks, reaching a zenith of 180–240 mm Hg after 4 months. Elevated blood pressures were maintained in both sexes. After 20 months, the male SHR began to die of myocardial infarction and hypotensive crisis. Heart and adrenal gland weight increased progressively not only during the phase of rapidly rising blood pressure but also during the period of plateaued but sustained high blood pressure. RIA of plasma levels of aldosterone, deoxycorticosterone, corticosterone, and PRL, under both quiescent and mildly stressful conditions, demonstrated that the pituitaryadrenal axis of SHR progressively increases its propensity to respond to stress with maturation. This capacity to respond to stress was maintained despite the severe high blood pressure and the attainment of relative old age, i.e. 2 yr. An incremental change in circulating PRL, corticosterone, and aldosterone as early as 2 months of age, when blood pressure levels are beginning to rise, suggests that there may be some connection between the genetically programmed pathogenesis of the spontaneous hypertension and the progressively increasing (with age) sensitivity of the pituitary-adrenal axis to stress.