O₂-dependent prostanoid synthesis activates functional PGE receptors on corpus cavernosum smooth muscle

Abstract

We have previously demonstrated that decreased O2 tension inhibits prostaglandin synthesis from human corpus cavernosum smooth muscle cells in static culture over 8-18 h (R. B. Moreland et al., Molecular Urology 2: 41-47, 1998). In this report, an experimental system was designed that allowed determination of the effects of O2 tension changes over the time frame of physiological penile erection. Human corpus cavernosum smooth muscle cells were cultured on microcarrier beads in enclosed stirrer flasks so that rapid changes of O2 tension could be modulated. After 18 h of equilibration at 30-40 mmHg to simulate blood PO2 at penile flaccidity, O2 tension was increased to 100 mmHg for 1 h and then returned to 30-40 mmHg. Media samples were withdrawn for prostanoid synthesis and cell samples were taken for cAMP determinations. After 18 h of 30-40 mmHg PO2 values, prostanoid synthesis by human corpus cavernosum smooth muscle cells was low (0.1-0.7 pmol/10(6) cells). When PO2 was increased to 100 mmHg, a rapid increase in PGE2 >> PGF2alpha > PGD2 was observed (thromboxane A2 was undetectable), which peaked at 5.7 pmol PGE2/10(6) cells. Increased O2 tension correlated with increased PGE2 and increased intracellular synthesis of cAMP. The prostaglandin G/H synthase inhibitor indomethacin or the E prostanoid (EP2)-selective antagonist AH-6809 each inhibited the O2-tension-dependent increases in cAMP. These data support a role of differential O2 tension in the penis in the smooth muscle synthesis of PGE2, which in turn increases cAMP synthesis via EP2 receptors.

Expression of functional prostaglandin D (DP) receptors in human corpus cavernosum smooth muscle

“…2 We have previously demonstrated that PGE 1 causes cAMP levels to increase to 750 -1000 pmol=mg protein in human cavernosal smooth muscle cells through either the EP2 and=or EP4 receptors. 12,16 This PGE 1 -induced increase in cAMP synthesis was observed to be proportional to the relaxation response. In contrast, the induction of cAMP synthesis by BW245C in the present study appears much less robust than the efficacy of DP agonists on smooth muscle relaxation.…”

“…Human corpus cavernosum smooth muscle cells were grown from tissue explants 17 and cultured on Cytodex TM III microcarrier beads (Pharmacia, Piscataway, NJ), as previously described for human corpus cavernosum smooth muscle cells 12 and human umbilical endothelial cells. 19 Cells were grown and maintained under low shear conditions at media PO 2 corresponding to blood PO 2 during penile erection (100 mm Hg).…”

Functional prostaglandin E (EP) receptors in human penile corpus cavernosum

“…We have previously demonstrated the expression of EP2 and EP4 receptors in HCC and in cultured SMC using RT-PCR. 6 We were not successful in demonstrating EP1 receptor mRNA expression either by RNase protection or RT-PCR (data not shown) despite pharmacologic functional evidence suggesting the presence of these receptors (see below).…”

“…4,5 In addition, corpus cavernosum smooth muscle cells (SMC) in culture have been shown to synthesize PGD 2 , PGE 2 and PGF 2a , all of which are regulated by oxygen tension. 6 Of these eicosanoids, only PGE 1 has been reported to relax penile cavernosal smooth muscle. [7][8][9][10] Further, arachidonic acid, the precursor of PGE 2 , can relax human corpus cavernosum (HCC) smooth muscle in the presence of thromboxane receptor antagonists, a process blocked by the prostaglandin G/H synthase inhibitor indomethacin.…”

Gene and protein expression profiles of prostaglandin E2 receptor subtypes in the human corpus cavernosum

“…They have found the expression of EP2, EP3I and EP3II receptor mRNA; however, the expression of EP1 and EP4 receptor mRNA was not determined. But before, Moreland et al 15 reported that human corpus cavernosum express both EP2 and EP4 receptor mRNA. In addition, there are eight isoforms of EP3 receptor.…”