Stress hypertension: the "wrong" genes in the "wrong" environment.

Jim Henry demonstrated an animal's society can induce an increase in blood pressure and its cardiovascular sequale. He recognized that the stress required to elevate blood pressure was a function of the genetically determined behavioral traits of the mice used. He termed some strains aggressive, others peaceable. Being highly inbred (indeed isogenic strains) it was intriguing to find that the behavior of these genetically identical individuals could differ markedly once placed in a society that decreased territory. A dominant or "king" mouse emerged. Other non-dominant males were aggressive and striving to be king. Adrenal medullary systems were activated and renins high. Others huddled in one cage and appeared to have given up. Jim called them depressed. Their adrenal cortex was hyperplastic suggesting pituitary adrenal axis activation as in depression, their renin was low and corticosterone high. In rats, careful selection of a strain genetically aggressive had to be combined with titration of societal stress to reliably induce hypertension. Its likely that humans retain some, if not all, of these variations, i.e. some respond to stress with an increase in blood pressure and others do not, some respond via the sympathetic pathway and others by adrenal cortical activation. The suggestion that African American's high blood pressures is due to stress is relevant to the Henry paradigm and the known genetic influences on sodium retention in blacks. The integration of this paradigm with the genetically increased sensitivity to the blood pressure raising effects of dietary sodium in blacks is proposed and discussed.