Prostanoid production in rabbit corpus cavernosum: I. regulation by oxygen tension

To investigate the effects of oxygen tension on prostanoid synthesis in rabbit penile corpus cavernosum tissue (RCC) in organ culture.

Strips of rabbit corpus cavernosum were incubated in organ culture media under varying oxygen conditions (0%, 12% and 21% oxygen), in the presence or absence of acetylcholine and arachidonate stimulation. Prostanoids were measured in collected media by radioimmunoassay. Prostaglandin H synthase (PGHS) protein levels and mRNA PGHS expression were measured under both 0% and 21% oxygen conditions.

Basal and acetylcholine-stimulated PGI2 release was progressively diminished as a function of diminishing oxygen tension (pO2 from approximately 165 to 25 mm.Hg). The basal and stimulated production of other prostanoids, thromboxane A2, PGF2alpha, and PGE2, was also significantly inhibited under 0% oxygen (approximately 25 mm.Hg) conditions. However, incubation under 0% oxygen did not alter PGHS protein levels nor mRNA PGHS expression. Cavernosal strips incubated under 0% oxygen but supplemented with exogenous arachidonate (10 microM.) maintained significantly lower PGI2 production than tissues exposed to 21% oxygen (approximately 165 mm.Hg).

These data demonstrate that oxygen tension regulates prostaglandin production in corporal tissue. The reduction in prostanoid production during hypoxia can be attributed to inhibition of PGHS activity rather than the expression of the enzyme. In view of the role of PGI2 as an inhibitor of platelet aggregation and white cell-endothelial adhesion, our findings may provide mechanistic insight into the alteration in corporal blood homeostasis ischemic-hypoxic priapism.