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Activation of (arachidonyl) phosphatidylinositol turnover in rabbit neutrophils by the calcium ionophore A23187.

ABSTRACT: The addition of the Ca2+ ionophore A23187 to rabbit neutrophils stimulated [14C]arachidonic acid incorporation into phosphatidylinositol and lysosomal enzyme secretion. A significant increase in phosphatidylinositol labelling was observed after a 2 min exposure to 0.1 microM-ionophore A23187. Maximum increases in rate of labelling were obtained with 1 microM-ionophore A23187 within 1 min, declining to basal rates after 15 min. Similarly, maximum rate of enzyme release occurred during the first 2 min of exposure to ionophore and release was essentially complete by 15 min. Threshold and peak ionophore A23187 concentrations for stimulating both processes were identical. In contrast with the specificity of phosphatidylinositol labelling induced by 1 microM-ionophore A23187 in the absence of cytochalasin B, ionophore also significantly stimulated labelling of phosphatidylserine and phosphatidylethanolamine in the presence of cytochalasin B. With a threshold ionophore concentration (0.1 microM), the enhanced incorporation of arachidonate was relatively specific for phosphatidylinositol in cytochalasin-treated cells. Ionophore A23187 did not accelerate labelling of phosphatidylinositol by [14C]acetate or [14C]glycerol, indicating that ionophore A23187 does not stimulate phosphatidylinositol synthesis de novo, although it did promote [14C]palmitate and [32P]Pi incorporation into neutrophil phosphatidylinositol. However, the increase in phosphatidylinositol labelling with these latter precursors was generally slower in onset and much more modest in magnitude than that observed with arachidonic acid. These results support the hypothesis that a Ca2+-dependent phospholipase, which acts on the arachidonate moiety of phosphatidylinositol, is responsible for initiating at least certain of the membrane events coupled to the release of secretory product from the neutrophil.

SUBMITTER: Rubin RP

PROVIDER: S-EPMC1162774 | biostudies-other | 1981 Feb

REPOSITORIES: biostudies-other

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Project description:BackgroundIntracytoplasmic sperm injection (ICSI) has tremendous advantages for resolving the problem of male infertility. However, ICSI fertilization can fail in some patients because of various reasons, primarily because of the failure of oocyte activation. Oocytes have been activated using calcium ionophore (A23187) in previous clinical cases of ICSI fertilization failure. However, studies on the efficiency of calcium ionophore (A23187) activation, its effects on the developmental potential of embryos, and its effects on pregnancy outcomes after embryo transfer are relatively limited.MethodsIn this study, we investigated the safety and long-term efficacy of calcium ionophore (A23187) by analyzing its effects on fertilization, embryonic development, aneuploidy, and pregnancy outcomes in patients undergoing preimplantation genetic testing (PGT) cycles.ResultsComparative analyses of the activation followed by PGT (A-PGT) and PGT groups revealed no significant differences between the oocyte cleavage rate and high-quality embryo rate (98.19% vs. 98.63% and 63.13% vs. 68.39%, respectively, p > 0.05). Although the blastocyst formation rate was significantly lower in the A-PGT group than that in the PGT group (52.22% vs. 59.90%, p < 0.05), no significant difference was observed in the blastocyst aneuploidy rates of the two groups (24.49% vs. 24.55%, p > 0.05). Furthermore, no significant differences were observed between the two groups in terms of the live birth rate (43.75% vs. 52.99%), week of delivery, and birth weight of the infants after transfer of euploid blastocysts (p > 0.05). Furthermore, the 2PN rate, oocyte cleavage rate, blastocyst formation rate, and live birth rate were found to be significantly lower in the A-ICSI group than those in the ICSI group (p < 0.01), but there was no significant difference between the two groups in the week of delivery and birth weight of live births (p > 0.05).DiscussionThese results suggest that the use of calcium ionophore (A23187) activation as an option in cases of ICSI fertilization failure does not affect the ploidy of developing blastocysts and has no significant effects on the week of delivery or birth weight after transfer. Thus, we provide a scientific basis for the clinical safety of oocyte activation using calcium ionophore (A23187).

Project description:1. The effects on phosphatidylinositol metabolism of three Ca(2+)-mobilizing glycogenolytic hormones, namely angiotensin, vasopressin and adrenaline, have been investigated by using rat hepatocytes. 2. All three hormones stimulate both phosphatidylinositol breakdown and the labelling of this lipid with (32)P. 3. The response to angiotensin occurs quickly, requires a high concentration of the hormone and is prevented by [1-sarcosine, 8-isoleucine]angiotensin, a specific angiotensin antagonist that does not prevent the responses to vasopressin and to adrenaline. This response therefore seems to be mediated by angiotensin-specific receptors. 4. [1-Deaminocysteine,2-phenylalanine,7-(3,4-didehydroproline),8-arginine] vasopressin, a vasopressin analogue with enhanced antidiuretic potency, is relatively ineffective at stimulating phosphatidylinositol metabolism. This suggests that the hepatic vasopressin receptors that stimulate phosphatidylinositol breakdown are different in their ligand selectivity from the antidiuretic vasopressin receptors that activate renal adenylate cyclase. 5. Incubation of hepatocytes with ionophore A23187, a bivalent-cation ionophore, neither mimicked nor appreciably changed the effects of vasopressin on phosphatidylinositol metabolism, suggesting that phosphatidylinositol breakdown is not controlled by changes in the cytosol Ca(2+) concentration. This conclusion was supported by the observation that hormonal stimulation of phosphatidylinositol breakdown and resynthesis persists in cells incubated for a substantial period in EGTA, although this treatment somewhat decreased the phosphatidylinositol response of the hepatocyte. The phosphatidylinositol response of the hepatocyte therefore appears not to be controlled by changes in cytosol [Ca(2+)], despite the fact that this ion is thought to be the second messenger by which the same hormones control glycogenolysis. 6. These results may be an indication that phosphatidylinositol breakdown is an integral reaction in the stimulus-response coupling sequence(s) that link(s) activation of alpha-adrenergic, vasopressin and angiotensin receptors to mobilization of Ca(2+) in the rat hepatocyte.

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Activation of (arachidonyl) phosphatidylinositol turnover in rabbit neutrophils by the calcium ionophore A23187.

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