Glycine transport in mouse eggs ad preimplantation conceptuses

Winkle, Lon J. Van; Haghighat, N.; Campione, Allan L.; Gorman, James M.

doi:10.1016/0005-2736(88)90185-x

Cited by 78 publications

(56 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although the substrate specificities of systems B 0,+ and b 0,+ are very similar, the latter reacts poorly with amino acids branched at the â_carbon (Van Winkle et al 1988a) and this does not fit with the good reactivity shown here for isoleucine and valine (Table 1). Other properties, which have been reported for system B 0,+ , that fit to the substrate specificity shown in Table 1 are the poor stereospecificity for ª_ and ¬_alanine (Van Winkle et al 1985), the relatively high affinity (Van Winkle et al 1985) and the lack of tolerance to N_methylation (Van Winkle, Haghighat, Campione & Gorman, 1988b). It seems pertinent to examine whether the results reported here may contribute to an explanation of the effects of amino acids on the secretion of AP hormones observed in vivo (see Introduction).…”

Section: Discussionmentioning

confidence: 59%

Mechanisms for stimulation of rat anterior pituitary cells by arginine and other amino acids

Alonso

Núñez

García‐Sancho

1997

The Journal of Physiology

View full text Add to dashboard Cite

Arginine and other amino acids are secretagogues for growth hormone and prolactin in the intact animal, but the mechanism of action is unclear. We have studied the effects of amino acids on cytosolic free calcium concentration ([Ca2+]i) in single rat anterior pituitary (AP) cells. Arginine elicited a large increase of [Ca2+]i in about 40 % of all the AP cells, suggesting that amino acids may modulate hormone secretion by acting directly on the pituitary. Cell typing by immunofluorescence of the hormone the cells store showed that the arginine‐sensitive cells are distributed uniformly within all the five AP cell types. The arginine‐sensitive cells overlapped closely with the subpopulation of cells sensitive to thyrotrophin‐releasing hormone. Other cationic as well as several neutral (dipolar) amino acids had the same effect as arginine. The increase of [Ca2+]i was dependent on extracellular Ca2+ and blocked by dihydropyridine, suggesting that it is due to Ca2+ influx through l‐type voltage‐gated Ca2+ channels. The [Ca2+]i increase was also blocked by removal of extracellular Na+ but not by tetrodotoxin. The substrate specificity for stimulation of AP cells resembled closely that of the amino acid transport system B0,+. We propose that electrogenic amino acid influx through this pathway depolarizes the plasma membrane with the subsequent activation of voltage‐gated Ca2+ channels and Ca2+ entry. Amino acids also stimulated prolactin secretion in vitro with a similar substrate specificity to that found for the [Ca2+]i increase. Existing data on the stimulation of secretion of other hormones by amino acids suggest that a similar mechanism could apply to other endocrine glands.

show abstract

Section: Discussionmentioning

confidence: 59%

Mechanisms for stimulation of rat anterior pituitary cells by arginine and other amino acids

Alonso

Núñez

García‐Sancho

1997

The Journal of Physiology

View full text Add to dashboard Cite

show abstract

“…However, we unexpectedly found that GLYT1 in 1-cell mouse embryos did not transport betaine (Hammer and Baltz, 2002). Furthermore, established mammalian organic osmolyte transporters shown to accept betaine (BGT1 and System A) were not present in early PI mouse embryos (Van Winkle et al, 1988;Hammer and Baltz, 2002). Proline also effectively protected PI mouse embryo development against increased osmolarity (Dawson and Baltz, 1997;Baltz, 2001).…”

mentioning

confidence: 78%

“…We focused first on glycine, since early PI embryos were known to transport glycine at a high rate, via the GLYT1 (slc6a9) transporter (Hobbs and Kaye, 1985;Van Winkle et al, 1988), which is a member of the Na þ -and Cl À -dependent neurotransmitter transporter (NTT or SLC6) family (Nelson, 1998;Hoglund et al, 2005). Also, a large amount of glycine is present in the oviduct, with mouse oviductal fluid containing 0.5-3.0 mM glycine (Guerin et al, 1995;Harris et al, 2005) and similarly high amounts in tubal fluid of other mammals.…”

mentioning

confidence: 99%

The organic osmolytes betaine and proline are transported by a shared system in early preimplantation mouse embryos

Anas¹,

Hammer²,

Lever

et al. 2006

Journal Cellular Physiology

View full text Add to dashboard Cite

Betaine and proline protect preimplantation mouse embryos against increased osmolarity and decreased cell volume, implying that they may function as organic osmolytes. However, the transport system(s) that mediates their accumulation in fertilized eggs and early embryos was unknown, and previously identified mammalian organic osmolyte transporters could not account for their transport. Here, we report that there is a single saturable transport component shared by betaine and proline in 1-cell mouse embryos. A series of inhibitors had nearly identical effects on both betaine and proline transport by this system. In addition, K i values for reciprocal inhibition of betaine and proline transport were $100-300 mM, similar to K m values ($200-300 mM) for their transport, and both had similar maximal transport rates (V max ). The K i values for inhibition of betaine and proline transport by dimethylglycine were similar ($2 mM), further supporting transport of both substrates by a single transport system. Finally, betaine and proline transport each required Na þ -and Cl À . These data were consistent with a single, Na þ -and Cl À -requiring, betaine/proline transport system in 1-cell mouse embryos. While betaine was only transported by a single saturable system, we found an additional, less conspicuous proline transport route that was betaine-insensitive, Na þ -sensitive, and inhibited by alanine, leucine, cysteine, and methionine. Furthermore, we showed that betaine, like proline, is present in the mouse oviduct and thus could serve as a physiological substrate. Finally, accumulation of both betaine and proline increased with increasing osmolarity, consistent with a possible role as organic osmolytes in early embryos.

show abstract

“…Glycine is also abundant in the embryo's environment in vivo, with 0.5-3.0 mM glycine in oviductal fluid (Guerin et al, 1995;Harris et al, 2005), far above the half-maximally effective concentration of 50 mM for protecting embryo development against increased osmolarity (Dawson and Baltz, 1997). Additionally, a single, robust glycine transport mechanism was shown to be present and active in early preimplantation embryos until compaction, and had been identified as the classical amino acid transport system designated GLY (Van Winkle et al, 1988).…”

Section: Organic Osmolyte Usage By Preimplantation Embryosmentioning

confidence: 99%

Cell volume regulation in mammalian oocytes and preimplantation embryos

Baltz

Zhou

2012

Molecular Reproduction Devel

View full text Add to dashboard Cite

SUMMARYThe earliest stages of preimplantation embryos are particularly sensitive to increased osmolarity, even within the physiological range. This sensitivity contributed to persistent developmental arrest, even when embryos were cultured in vitro in older, conditioned culture media, and seems to arise when embryos at the 1-and 2-cell stages accumulate inorganic ions used for cell volume homeostasis at too high a level, through activation of coupled Na þ /H þ and HCO 3 À /Cl À exchange. Such accumulation of inorganic ions can be disruptive since, above a certain level, the increased ionic strength disrupts cellular biochemistry and macromolecular functions and alters membrane potential. To counter this, embryos have evolved mechanisms of cell volume regulation that are unique to early preimplantation embryogenesis. The primary role of these is glycine accumulation via the GLYT1 transporter, with a secondary contribution by betaine accumulation via the SIT1 transporter. Independent cell-volume regulation first arises in the oocyte only after ovulation is triggered, when the strong oocyte-zona pellucida adhesion present in germinal vesicle stage oocytes in the ovarian follicle is released and GLYT1 becomes activated to begin accumulating glycine. Open questions still remain regarding how these processes are regulated.Mol. Reprod. Dev. 79: 821-831, 2012. ß

show abstract

Glycine transport in mouse eggs ad preimplantation conceptuses

Cited by 78 publications

References 33 publications

Mechanisms for stimulation of rat anterior pituitary cells by arginine and other amino acids

Mechanisms for stimulation of rat anterior pituitary cells by arginine and other amino acids

The organic osmolytes betaine and proline are transported by a shared system in early preimplantation mouse embryos

Cell volume regulation in mammalian oocytes and preimplantation embryos

Contact Info

Product

Resources

About