Aortic vascular and atrial responses to (±)‐1‐O‐octadecyl‐2‐acetyl‐glyceryl‐3‐phosphorylcholine

• Published in: British journal of pharmacology Vol. 79; no. 3; pp. 667 - 671
• Main Authors: Cervoni, P., Herzlinger, H.E., Lai, F.M., Tanikella, T.K.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.07.1983; Nature Publishing Group
• Subjects: Animals; Aorta - drug effects; Dose-Response Relationship, Drug; Heart Atria - drug effects; In Vitro Techniques; Male; Muscle Contraction - drug effects; Muscle, Smooth, Vascular - drug effects; Myocardial Contraction - drug effects; Platelet Activating Factor - administration & dosage; Platelet Activating Factor - analogs & derivatives; Platelet Activating Factor - pharmacology; Rats; Rats, Inbred Strains; Stimulation, Chemical
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1111/j.1476-5381.1983.tb10003.x

1 The effects of (±)‐1‐O‐octadecyl‐2‐acetyl‐glyceryl‐3‐phosphorylcholine (octadecyl‐AGPC) were studied in three types of aortic vascular smooth muscle preparations, namely, strips, rubbed and unrubbed rings, and an atrial preparation in normotensive rats. 2 In the resting tension state, octadecyl‐AGPC did not elicit significant contractions in either rubbed or unrubbed ring preparations at concentrations lower than 1 × 10−4m. However, at a concentration of 3 × 10−4 m, octadecyl‐AGPC markedly contracted both types of ring preparations. This contractile response was partially antagonized by pretreatment with reserpine and completely blocked by phentolamine (1 × 10−6m). 3 In preparations contracted with noradrenaline (NA), octadecyl‐AGPC elicited biphasic responses in intact ring preparations; an initial relaxation followed by contraction. Octadecyl‐AGPC induced only a slight contraction in strips and a slight relaxation in the rubbed ring preparation. 4 Octadecyl‐AGPC did not elicit any significant effect on chronotropy or inotropy at concentrations up to 3 × 10−5 m. When the concentration was 1 × 10−4 m, octadecyl‐AGPC produced significant positive chronotropic and inotropic effects on spontaneously beating right and electrically driven left atrial preparations, respectively. Both effects were blocked by propranolol (5 × 10−8m); reserpine pretreatment antagonized only the chronotropic response. 5 In [3H]‐dihydroalprenolol ([3H]‐DHA) binding studies, octadecyl‐AGPC had a Kd of 427.85 μm and thus was much less potent than isoprenaline (Kd = 465.10 nm) or propranolol (Kd = 4.4 nm) in displacing [3H]‐DHA in rat cardiac membrane preparations. 6 In conclusion, relaxation and contraction induced by octadecyl‐AGPC in aortic preparations is an indirect rather than a direct effect. An unknown factor released from endothelial cells is responsible for aortic smooth muscle relaxation by octadecyl‐AGPC while released NA appears to be responsible for aortic vascular contraction and for the positive chronotropic and inotropic effects in the atrial preparations.