Extracellular ADP and ATP stimulated the synthesis of prostacyclin - as reflected by the release of 6-keto-PGF1 alpha - in the rabbit aorta, the rabbit pulmonary artery and the rat aorta. A doubling of 6-keto-PGF1 alpha output was produced by 3 microM ADP. Adenosine had no effect and the stimulation by ADP was blocked by quinidine, but not by theophylline. This stimulation was abolished by indomethacin and lost after mechanical removal of the endothelium. Stimulation of vascular prostacyclin synthesis by ADP released from aggregating platelets could help localize thrombus formation to areas of vascular damage.

Lupin is toxic because of its alkaloid content, sparteine and lupanine in particular. Although the pharmacological properties of sparteine are well known those of lupanine have not been much studied. This paper reports procedures for extraction, purification and crystallization of lupanine, and methods for the preparation of an extract for injection of Lupinus mutabilis Sweet, and for the determination of the acute toxicity and maximum non-lethal dose (DL0) of lupanine, sparteine and lupin extract in the mouse. The three substances were tested on the central nervous system (CNS) for locomotor activity, for interaction with specific drugs used for treatment of the CNS (the stimulant drugs amphetamine and pentetrazol and the depressant drugs pentobarbital and chlorpromazine) and for analgesic activity. The results indicate that lupanine and lupin extract are less toxic than sparteine and that at the doses studied the three products have a weak sedative effect on the CNS.

The acute effect of in vitro deendothelialization on the production of prostacyclin (PG12) by the rabbit aorta has been investigated. The effectiveness of removing endothelium by rubbing it against filter paper or scraping it with a scalpel was demonstrated by scanning electron microscopy and en face examination after silver staining. Endothelium removal produced an immediate stimulation of PGI2 release, resulting in 408% of the control after rubbing and 367% of the control after scraping, during the first 30-min period of incubation. This increased production of PG12 gradually declined over time to reach values similar to the control after 2 h. At that time, the deendothelialized aorta was totally unresponsive to the stimuli that increase PG12 release in the intact aorta (acetylcholine, ADP, ionophore A23187, and arachidonic acid). The enhanced production of PG12 in the deendothelialized aorta was associated with an increased release of free arachidonic acid (353% of the control): in contrast with PG12, this stimulation was maintained for at least 150 min. A transient exposure of the deendothelialized aorta to ibuprofen (250 1M) was followed by a rebound of PG12 production, which was also prolonged by BW-755C (3-10 ;&M). In conclusion, removal of the endothelium triggered an immediate and sustained mobilization of free arachidonic acid in the rabbit aorta: the resulting increase of P012 production was short-lived, probably as a consequence of cyclooxygenase self-inactivation. Our results indicate that the subendothelium has a significant capacity to produce PGI2, but that this capacity is expressed only briefly.

The production of prostacyclin by rings of rabbit aorta was assessed by the radioimmunoassay of 6-keto-PGF1 alpha. In steady-state conditions, the rings released 11 ng 6-K-PGF1 alpha per 100 mg tissue in 30 min. Acetylcholine increased this output: a significant effect was detected at 1 microM and at 10 microM the amplitude of stimulation was 10-fold. The production of PGE2 and PGF2 alpha was also increased, but to a lesser extent. The stimulatory action of acetylcholine was mimicked by carbamylcholine and inhibited by atropine; it was abolished in a calcium-free medium. Dog and rat aorta also produced more 6-K-PGF1 alpha in response to cholinergic agonists. A short rubbing of the intimal surface of the aorta removed the layer of endothelial cells and completely abolished the cholinergic effect. It is concluded that in the aorta, cholinergic agonists, acting on a muscarinic receptor, stimulate the production of prostacyclin by endothelial cells.

Epinephrine and norepinephrine (1-10 microM) stimulated the release of prostacyclin (PGI2) from the rabbit aorta in vitro. The stimulation was maintained for at least 2 h in the continuous presence of epinephrine. Phenylephrine mimicked this effect, whereas the selective alpha 2-agonist UK-14,304 was completely ineffective. The action of epinephrine was abolished by prazosin (1 microM) and was maintained in the presence of yohimbine. Epinephrine or phenylephrine neither increased the basal release of PGI2 from bovine aortic endothelial cells nor potentiated the stimulatory action of adenine nucleotides, which is mediated by P2-purine receptors. The response to epinephrine was lost in freshly deendothelialized strips of rabbit aorta, possibly because of cyclooxygenase self-inactivation. The response recovered however following overnight incubation of these strips in a cell culture medium. The response to epinephrine was mimicked by neither phorbol 12-myristate,13-acetate nor ionophore A23187. It was not inhibited by pretreatment with pertussis toxin. It is concluded that adrenergic agents stimulate the vascular production of PGI2, by activating alpha 1-receptors located on smooth muscle cells.