Osmolarity changes can enhance the release of renin from human chorion

Sections of human chorion were perfused with an aerated buffer for 5 hours. Samples were collected every 20 minutes and the concentration of active and total renin in the perfusate was measured. Substitution of the initial bicarbonate buffer (281 mosm/L) with a buffer of 251 mosm/L doubled the rate at which active and inactive renin were released into the perfusate. When the osmolarity of the solution was reduced by 60 mosm/L, a threefold rise in the concentration of active renin and a sixfold rise in that of total renin was seen. However, these effects were transient, and renin secretion decreased before osmolarity was raised to the previous value.