Location of Renin in Rabbit Uterus by Help of Microdissection

The location of renin was investigated on microdissected cryostat section of freeze‐dried uterine tissue from three non‐pregnant and six 28 days pregnant rabbits. A coarse separation of the uterine layers of the mesometrial part of the wall showed about the same high renin content in the endometrium and the circular myometrium, but a much lower content in the longitudinal myometrium. In the antimesometrial part of the wall the renin content was lower in the endometrium than in the two muscle layers. In the pregnant endometrium renin was mainly located to the endometrial stroma in which high values were measured in smaller vessels (40–60 μ in diameter). In the pregnant myometrium renin was located both to the arteries, arterioles and venoles, the renin concentration being especially high in the smaller vessels (30–60 μ), the values of the venoles exceeding those of the arterioles. In addition to the isolated vessels renin was found in muscle and connective tissue devoid of arterioles and venoles. This can be due either to ubiquitous occurrence of renin producing cells, or to release of renin from the vessels to the extracellular fluid.