The effects of arterial blood gas tensions on pressor responses to angiotensin II in the pithed rat.

The influence of arterial blood gas tensions on angiotensin II-mediated pressor responses in the pithed rat was studied by altering the inspired gas mixture at a fixed tidal volume. When rats were ventilated to produce physiological Pa, CO2 levels (35-40 mmHg) responses to boluses of angiotensin II were greater with increasing Pa, O2 over the Pa, O2 range of 65-460 mmHg. There was no difference in response to angiotensin II over the Pa, CO2 range studied (18-50 mmHg). All variations in response to angiotensin II were attributable to changes in Pa, O2. Since arterial blood gas tensions, especially the Pa, O2, modulate pressor responses to boluses of angiotensin II, the physiological effects of this hormone may be most fruitfully explored in rats ventilated to produce normal arterial blood gas tensions.