Acid activation of renin in rabbit uterus

During the first 2 days post-partum there is a rapid fall in the uterine renin content of the rabbit. A similar loss of renin can be reproduced in vitro when pregnant and post-partum and to a lesser degree non-pregnant uterine tissue slices are incubated at pH 7.4 at 37 degrees C. When a secondary incubation of these previously incubated preparations is performed at pH 4.8 an activation of renin is seen. There was not an inverse correlation between the amounts of renin lost during the primary incubation at pH 7.4 and the amounts of renin activated during the secondary incubation at pH 4.8. In similarly incubated preparations of kidney cortex, where only a small per cent of the initial renin content is lost during the primary incubation at pH 7.4, no activatable renin is seen.