ENDOTHELIN-1 AND BREATHING PATTERN IN PIG

The respiratory and vascular effects of Endothelin-1 (ET-1) were evalu ated in six anesthetized and spontaneously breathing pigs. ET-1 was ad ministered intrajugularly as a bolus of 100 pmol/Kg. Then the vascular effects of the peptide, administered at the same dose, were evaluated in the same pigs during mechanical ventilation. Our results show that during mechanical ventilation ET-1 has a biphasic effect on pulmonary and systemic arterial pressure, while in spontaneously breathing pigs it affects only pulmonary arterial pressure. Our results also show th at ET-1 changes the breathing pattern, lengthening the inspiration and expiration times. During pulmonary hypertension, the lengthening migh t be due to a vagal reflex, while during pulmonary hypotension it migh t be due to direct involvement of ET-1 in the control of the breathing pattern.