Renin-Like Substance in Blood after Hemorrhage.

Discussion and ConclusionsThe observed phenomena are consistent with the concept that the blood of the normal animal, with normal pulse pressure, contains activator but no renin whereas blood taken after hemorrhage when the pulse pressure may be low contains demonstrable amounts of a renin-like substance. Moreover, since the gut always responds slowly to posthemorrhagic blood, it seems likely that this blood contains a diminished amount of activator, since the usual response to a mixture of renin and activator is prompt. Prehemorrhagic blood, which according to this concept contains no renin is incapable of sensitizing the gut to either pre- or posthemorrhagic blood. The results in the single exceptional experiment already cited might be explained by assuming a low renin activator or high renin inhibitor content in the normal blood of the animal in question.If, as it appears, the renin content of blood increases after hemorrhage, when the effect of such an increase would help restore the blood pressure to normal levels, these findings support the view that the kidney acts as an organ of internal secretion, preserving the homeostasis of the whole circulatory system by a humoral mechanism.The assay method here described is not specific for renin or renin activator and further experiments to make the identity of the active substances involved more certain are in progress.