The effects of pulmonary lymphatic obstruction on urine flow, sodium and potassium excretion were examined on anaesthetized, artificially ventilated New Zealand White rabbits. Pulmonary lymphatic obstruction was produced by raising the pressure in a pouch created from the right external jugular vein. The experiments were performed on two groups of rabbits (non-hydrated and hydrated). 2. Pulmonary lymphatic obstruction caused a significant increase in urine flow in both groups of rabbits. After release of the obstruction, the urine flow returned to basal values. Urine flow (ml (10 min)-1) for both groups was initial control, 5.3 +/- 0.9; lymphatic obstruction, 8.9 +/- 1.0; final control, 6.2 +/- 0.7 (means +/- S.E.M.; n = 21, P < 0.025). 3. The increase in urine flow was not accompanied by significant changes in concentration of sodium and potassium in urine. Sodium excretion increased significantly only in the hydrated rabbits. 4. The increase in urine flow was abolished by bilateral cervical vagotomy and by renal nerve sectioning. Cooling the cervical vagi to 8 degrees C also abolished the response. 5. Pulmonary lymphatic obstruction did not produce any significant change in heart rate, mean arterial blood pressure, mean right atrial pressure and peak airway pressure. 6. These findings suggest that obstructing the lymph drainage from the lung results in a reflex increase in urine flow. The afferent pathway for this reflex resides in the myelinated fibres of the vagi and the efferent pathway in the renal nerves. The rapidly adapting receptors of the airways are likely to be the receptors involved.
