The effect of oestrogen and progesterone on the pressor action of angiotensin in the rat.

1. A comparison was made between the pressor responses to angiotensin in rats during different stages of the oestrous cycle, pregnancy, pseudopregnancy and also following oestrogen and progesterone treatment.2. No evidence for an effect of oestrogen on the response to angiotensin was found.3. Pregnancy and pseudopregnancy were found to diminish the pressor response to angiotensin.4. Progesterone treatment also diminished the response to angiotensin.5. It is suggested that the decrease in pressor response in pregnancy and pseudopregnancy is attributable to progesterone.6. The possible mode of action of progesterone is discussed.