Bicarbonate sensitive soluble adenylyl cyclase (sAC) generates the cAMP in aqueous humor (AH)

Abstract

Purpose: Recently we demonstrated that sAC a bicarbonate sensitive enzyme that catalyzes the conversion of ATP to cAMP plays a role in regulating outflow facility in mice. sAC is highly expressed in ciliary body but cold not be detected in drainage tissues implying a communicative pathway linking the cilliary body to regulation of outflow facility. In this study we aimed to determine whether cAMP is present in the AH of mice and whether it is generated by sAC.

Methods: AH was collected from the eyes of 3-6-month old sAC knock-out (KO) mice or WT litermates by cannulation of the anterior chamber with borosilicate glass microneedles. AH collection was performed between 2:00 PM and 4:00 PM to avoid the influence of circadian dynamics on our measurements. AH from both eyes of four mice were pooled and cAMP concentration determined using a commercial ELISA kit (Bio-Rad).

Results: Levels of cAMP in AH of sAC KO mice were 0.37 ± 0.59 pmol/ml (mean±sd, n=3) significantly different (p < 0.05) from the 2.67 ± 1.33 pmol/ml (mean±sd, n=3) measured in litermate controls.

Conclusions: cAMP levels in sAC KO mice were reduced ~7.25 fold. These findings suggest that cAMP in AH is generated primarily by sAC. Further studies are necessary to understand the effects of varying cAMP in AH on outflow facility.

Keywords: 455 ciliary body • 633 outflow: trabecular meshwork • 447 cell-cell communication