AGGRAVATING EFFECTS OF ISOLATED CAGING ON THE DEVELOPMENT OF HYPERTENSION AND ITS COMPLICATIONS IN STROKE-PRONE SPONTANEOUSLY HYPERTENSIVE RATS (SHRSP) AND WISTAR-KYOTO RATS (WKY)

Stroke-prone spontaneously hypertensive rats (SHRSP) and normotensive Wistar-Kyoto rats (WKY) were maintained in isolation or in group to analyze the effect of isolation, one type of emotional stress, on the development of hypertension and its complications. SHRSP kept isolated during the whole or a half of the experimental period developed severer hypertension within a shorter period than those kept together with other animals throughout the experiment, and showed significantly higher incidences of cerebral stroke (40 or 33%) than the latter (8.3%). Histological and pathophysiological studies revealed pituitary-adrenal and cardiac hypertrophy accompanying more accelerated urinary epinephrine (E) excretion which indicated emotional stress caused by isolation might aggravate pathological lesions in hypertension. Neither WKY in isolation nor in groups developed hypertension, although isolated WKY had significantly heavier pituitary and adrenal glands accompanied with more accelerated urinary E and calcium excretions than WKY kept in groups.