Adenosine potentiates forskolin‐induced delay of meiotic resumption by mouse denuded oocytes: Evidence for an oocyte surface site of adenosine action

Abstract

Adenosine is present in the mouse follicular fluid and has been shown to interfere with oocyte maturation in vitro. To clarify the mechanism of adenosine action on meiotic arrest, we have characterized the synergistic action of this purine with forskolin on the meiotic resumption of mouse denuded oocytes. Forskolin delays meiotic resumption by approximately 1 hour; adenosine at concentrations ranging between 30-750 microM has no significant effect. Conversely, adenosine treatment together with forskolin produces a further delay in the resumption of meiosis. This adenosine effect is dose-dependent and mimicked by adenosine analogs like N6-phenylisopropyl adenosine (PIA), 2-chloroadensoine (2-CLA), 5'-N-ethylcarboxamide (NECA). Dipyridamole, which inhibits adenosine transport, does not prevent the meiosis-arresting synergistic effect of adenosine with forskolin. Adenosine causes a 50% increase of adenosine triphosphate (ATP) content in the oocyte. However, this increase is not directly responsible for the observed delay in oocyte maturation for the following reasons: (1) the dose response of inhibition of meiotic resumption does not correlate with the doses of adenosine producing an increase in ATP; (2) dipyridamole blocks the increase in intracellular ATP, but it has no effect on the adenosine inhibition of maturation; (3) adenosine analogs inhibit oocyte maturation but do not affect intracellular ATP levels. These results suggest that the synergism of adenosine with forskolin on meiotic arrest does not require uptake of the nucleoside nor its conversion to ATP and that the adenosine effects are exerted at the level of the oocyte plasma membrane.

Adenosine levels in the postimplantation mouse uterus: Quantitation by HPLC‐fluorometric detection and spatiotemporal regulation by 5′‐nucleotidase and adenosine deaminase

“…This primitive morphogenetic system illustrates the utility of adenosine as a regulatory link between cellular metabolism and cell function. Other studies have shown the ability of adenosine to regulate vascular development (Dusseau et al, 1986;Adair et al, 1989), meiotic maturation of the oocyte (Eppig et al, 1985;Salustri et al, 1988), and embryonic limb-bud outgrowth (Knudsen and Elmer, 1987). These data suggest that adenosine may mediate intercellular interactions although its role in development is not understood.…”

Exogenous Adenosine Reduces the Mitochondrial Membrane Potential of Murine Oocytes During the Latter Half of In Vitro Maturation and Pronuclear Formation Following Chemical Activation

“…Following binding to the receptors at the cell surface, adenosine acts through the adenylate cyclase pathway. The receptors have been known to be expressed in both oocytes [32] and cumulus cells [33]. Adenosine A1 and A3 receptors have been known to activate adenylate cyclase, and conversely, A2 receptors inhibit adenylate cyclase [34].…”

Hypoxanthine Regulation of Oocyte Maturation in the Mouse: Insights Using Hypoxanthine Phosphoribosyltransferase-Deficient Animals1

“…More than 10 years ago, the purines, hypoxanthine (HX) and adenosine, were identified as components of follicular fluid that brought about meiotic arrest when added to cultures of spontaneously maturing mouse oocytes [6,7]. An inhibitory effect of these purines on spontaneous oocyte maturation has since been confirmed in numerous species, including the mouse [8][9][10][11], rat [12,13], cow [14], monkey [15], hamster [16], pig [17], and rabbit [18]. In addition, a sizable body of evidence has implicated the purine metabolic pathways as critical participants in the regulation of meiotic arrest (see [19] for review).…”