No abstract

The endogenous cannabinoid receptor agonist anandamide is present in central and peripheral tissues. As the kidney contains both the amidase that degrades anandamide and transcripts for anandamide receptors, we characterized the molecular components of the anandamide signaling system and the vascular effects of exogenous anandamide in the kidney. We show that anandamide is present in kidney homogenates, cultured renal endothelial cells (

The mechanisms by which synchronized embryonic development to the blastocyst stage, preparation of the uterus for the receptive state, and reciprocal embryouterine interactions for implantation are coordinated are still unclear. We show in this study that preimplantation embryo development became asynchronous in mice that are deficient in brain-type (CB1) and/or spleen-type (CB2) cannabinoid receptor genes. Furthermore, whereas the levels of uterine anandamide (endocannabinoid) and blastocyst CB1 are coordinately down-regulated with the onset of uterine receptivity and blastocyst activation prior to implantation, these levels remained high in the nonreceptive uterus and in dormant blastocysts during delayed implantation and in pregnant, leukemia inhibitory factor (LIF)-deficient mice with implantation failure. These results suggest that a tight regulation of endocannabinoid signaling is important for synchronizing embryo development with uterine receptivity for implantation. Indeed this is consistent with our finding that while an experimentally induced, sustained level of an exogenously administered, natural cannabinoid inhibited implantation in wild-type mice, it failed to do so in CB1 ؊/؊ /CB2 ؊/؊ double mutant mice. The present study is clinically important because of the widely debated medicinal use of cannabinoids and their reported adverse effects on pregnancy.Previous investigation suggested that cannabinoid exposure has adverse effects on pregnancy outcome (reviewed in Refs. 1-5). Cannabinomimetic drugs interact with two types of cannabinoid receptors, brain-type (CB1) and spleen-type (CB2) (6 -9). These receptor subtypes are negatively coupled to adenylate cyclase and to N-type and P/Q-type calcium channels and positively coupled to mitogen-activated protein kinase and to A-type potassium channels through G i/o proteins (7, 10). CB1 is expressed in brain and other peripheral tissues (7-11). CB2 is expressed primarily in immune tissues including the spleen, leukocytes, and tonsils (12). We have previously shown that CB1 is expressed in the preimplantation mouse embryo at much higher levels than in the brain (1, 2). The discovery of cannabinoid receptors led to the identification of endogenous cannabinoid ligands, N-arachidonoylethanolamine (anandamide), and 2-arachidonoylglycerol (13-17). We observed that anandamide is synthesized in the pregnant mouse oviduct and uterus (18) and that its levels are far higher in the uterus than in any other mammalian tissue examined (3). However, anandamide levels are significantly lower at implantation sites than at interimplantation sites, suggesting endocannabinoid ligandreceptor signaling during implantation (3). Indeed anandamide at higher levels adversely affects embryo development and implantation, whereas at lower levels it stimulates embryo growth and differentiation via CB1 (1-5). Interestingly, 2-arachidonoylglycerol is present in the mouse uterus at amounts similar to or lower than the lowest anandamide levels (1-5 nmol/g of tissue), and its level does not ...

Anandamide (N-arachidonoylethanolamine) is an endogenous ligand for both the brain-type (CB1-R) and spleen-type (CB2-R) cannabinoid receptors. This investigation demonstrates that the periimplantation mouse uterus contains the highest levels of anandamide (142-1345 pmol͞ mol lipid P; 1-7 g͞g wet weight) yet discovered in a mammalian tissue. The levels f luctuate with the state of pregnancy; down-regulation of anandamide levels is associated with uterine receptivity, while up-regulation is correlated with uterine refractoriness to embryo implantation. Anandamide levels are highest during the nonreceptive phase in the pseudopregnant uterus and in the interimplantation sites, and lowest at the site of embryo implantation. The lower levels of uterine anandamide at the implantation sites may be a mechanism by which implanting embryos protect themselves from the detrimental effects of this endogenous ligand. We also observed a reduced rate of zona-hatching of blastocysts in vitro in the presence of anandamide, and inhibition of implantation by systemic administration of a synthetic cannabinoid agonist CP 55,940. These adverse effects were reversed by SR141716A, a specific CB1-R antagonist. Taken together, the results suggest that an aberrant synthesis of anandamide and͞or expression of the cannabinoid receptors in the uterus͞embryo may account for early pregnancy failure or female infertility.