EFFECT OF PULMONARY LYMPHATIC OBSTRUCTION ON RABBIT URINE FLOW

1. The effects of pulmonary lymphatic obstruction on urine flow, sodiu m 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 righ t external jugular vein. The experiments were performed on two groups of rabbits (non-hydrated and hydrated). 2. Pulmonary lymphatic obstruc tion caused a significant increase in urine flow in both groups of rab bits. After release of the obstruction, the urine flow returned to bas al values. Urine flow (ml (10 min)(-1)) for both groups was: initial c ontrol, 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 u rine flow was not accompanied by significant changes in concentration of sodium and potassium in urine. Sodium excretion increased significa ntly only in the hydrated rabbits. 4. The increase in urine flow was a bolished 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 ch ange in heart rate, mean arterial blood pressure, mean right atrial pr essure and peak airway pressure. 6. These findings suggest that obstru cting the lymph drainage from the lung results in a reflex increase in urine flow. The afferent pathway for this reflex resides in the myeli nated fibres of the vagi and the efferent pathway in the renal nerves. The rapidly adapting receptors of the airways are likely to be the re ceptors involved.