Vasoconstrictor response of arterioles of the hamster cheek pouch to norepinephrine, prostaglandin H2, F2 alpha and carbocyclic thromboxane A2, a possible thromboxane A2 analogue.

Activated platelets produce thromboxane A2, a potent vasoconstrictor, which may play an important role in pathophysiological disturbances of microcirculation. Thromboxane A2 has a very short half life and has neither been isolated nor synthesized. Hence, the recently reported stable analogue, carbocyclic thromboxane A2 (CTA2), may become an interesting tool in pharmacological research. Its vasoconstrictor potency was compared in vivo with norepinephrine, prostaglandin H2 and F2 alpha using the following method: vessels of a hamster cheek pouch preparation were exposed to a superfusion to which the respective compounds were added to give 1 ng/ml to 0.1 mg/ml final concentrations. The decrease of vessel diameters was measured microscopically. Prostaglandin H2 was found to be the most potent vasoconstrictor followed by CTA2 and norepinephrine. Prostaglandin F2 alpha was least effective. The respective maximal vasoconstrictory responses did not differ significantly.