Abstract
In 1963 Okamoto and Aoki (1) had separated, by selective inbreeding, a colony of Wistar rat with 100% incidence of spontaneous hypertension. These rats were named spontaneously hypertensive rats (SH. rats) and, thereafter, various investigations of these SH. rats have been carried out by Okamoto et al. Although this SH. rat was distributed to many other laboratories in Japan as well as in other countries, the accurate longevity and motal causes of the SH. rats remain still to be reported. Because of high incidence of pulmonary and other infections in the conventional circumstances, many rats died in early age accidentally. These interfered seriously with the studies on the sequences of developments of hypertension and its pathophysiological etiology. The present work revealed that the maintenance of the SH. rats in the specific pathogen free (SPF) condition prevented the animals from the infections and brought about the exact observation of the causes of the spontaneous death and of the hypertensive lesions at the advanced ages.
