Oxygen-induced contraction in the guinea pig neonatal ductus arteriosus.
We investigated the mechanism of oxygen-induced contractions in ductus arteriosus isolated from neonatal guinea pig. A preparation equilibrated at low Po2 (less than 40 mm Hg) displayed a steady membrane potential of -54.8 mV. Application of oxygen (Po2 (less than approximately or equal to 300 mm Hg) resulted in: (1) stepwise development of tension coupled to action potentials and (2) sustained membrane depolarization to -32.9 mV associated with tonic contraction. Mechanical sensitivity to oxygen persisted at any[K]o up to 126 mM, and tension was always larger at a given [K]o or a given membrane potential with high Po2 than with low Po2. The change in membrane potential per decade change in [K]o was 35 mV at low Po2 and 16 mV at high Po2. Oxygen contractions occurred when the ductal strips were bathed in K-free media or exposed to ouabain. We conclude that oxygen caused a conductance change in the sarcolemma resulting in depolarization, which is coupled to contraction. There is also evidence of a membrane potential-independent contraction mechanism.
D000818:Animals; D004373:Ductus Arteriosus / Q000502:physiology*; D005260:Female; D006168:Guinea Pigs; D008564:Membrane Potentials; D009200:Myocardial Contraction / Q000187:drug effects*; D009467:Neuromuscular Depolarizing Agents / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D010100:Oxygen / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D011191:Potassium Deficiency; D011247:Pregnancy; D013314:Stress, Mechanical
D009467:Neuromuscular Depolarizing Agents; D010042:Ouabain; D011188:Potassium; D010100:Oxygen