PGE2 prevents anomalies induced by hyperglycemia or diabetic serum in mouse embryos.

Both a high level of D-glucose in the medium and serum from a diabetic rat can induce neural-tube fusion defects and growth retardation in cultured mouse and rat embryos. To test our hypothesis that a deficiency of PGs may be involved in the mechanism of hyperglycemia- and diabetic serum-induced teratogenesis and growth retardation, we added PGE2 to the medium of a whole mouse embryo culture containing either normal rat serum and 52.7 mM D-glucose (hyperglycemic) or diabetic rat serum and 22.2 mM D-glucose (diabetic). After a 24-h culture, 94% of hyperglycemic embryos and 81% of diabetic embryos had neural-tube fusion defects; in addition, the number of somites, the morphological score, and the protein content of the embryos were significantly lower than those of controls. Supplementing the medium with PGE2 at concentrations of 0.028-28.4 nM (hyperglycemic) or 28.4 nM (diabetic) significantly reduced the incidence of neural-tube defects and increased the number of somites, the morphological score, and the protein content. These results strongly support the hypothesis that the teratogenicity of diabetic serum, as well as the teratogenic action of hyperglycemic culture, are mediated through a deficiency of PGs.

Diabetic embryopathy.

Infants of diabetic mothers have three to four times the incidence of congenital malformations than that in the general population. These anomalies include defects of the neural tube, heart, urogenital system, skeleton and alimentary tract, and the caudal regression syndrome. The anomalies are considered to result from the maternal metabolic derangements. The mechanism has been suggested to involve a diminished turnover of phosphoinositide or arachidonic acid, or an excess of free oxygen radicals. As most of the anomalies in infants of diabetic mothers occur in the first few weeks of pregnancy, strict glycemic control beginning before conception appears mandated.

Biochemical basis of the diabetic embryopathy.

Signal transduction, phosphatidylinositol turnover and the arachidonic acid cascade appear to be a final common pathway involved in the differentiation and development of the early embryo and several embryonic organ structures. Disruption of this biochemical pathway by various agents may account for the occurrence of the diabetic embryopathy.

Cyclosporin A-induced embryopathy in embryo culture is mediated through inhibition of the arachidonic acid pathway.

Embryos from Swiss Webster mice were grown in culture for 24 hr starting at Day 8.5 of gestation to study the effects of cyclosporin A (CsA) on the developing embryo. The embryos exposed to concentrations of CsA from 0.1 microgram/ml to 10.0 micrograms/ml developed a significant increase in the incidence of malformations from 28.6% to 78.6%, as compared with the 6.8% incidence of malformations in the control embryos. These malformations included defects in the neural tubes, head folds, and facial arches. In addition, inhibition of embryonic growth in CsA-exposed embryos was shown by a lower somite number, crown-rump length, and protein content than those of the control embryos. Supplementation of the culture medium with arachidonic acid or prostaglandin E2 decreased the incidence of CsA-induced malformations by 50% to 70% and prevented the CsA-induced inhibition of growth. We conclude that CsA causes abnormal embryonic development in mouse embryo culture and that the mechanism of CsA-induced embryopathy involves inhibition of the arachidonic acid pathway.

John Lattimer lecture. Lipokinins: novel phospholipase A2 activators mediate testosterone effects on embryonic genitalia.

Testosterone-treated calf thymocytes produce increased amounts of proteins, termed lipokinins, that stimulate phospholipase A2 from snake venom and mammalian tissue. The induction of these proteins by testosterone is blocked by cycloheximide and, thus, requires new protein synthesis. These proteins activate phospholipase A2 stoichiometrically. They are inactivated by boiling, trypsin or alkaline phosphatase but not by deoxyribonuclease or ribonuclease. Lipokinins significantly repair the failure of masculinization in the Tfm mouse with an X-linked deficiency of androgen-receptor. Thus, the post-receptor effects of testosterone on embryonic genitalia may be mediated through stimulation of phospholipase A2 by lipokinins. Moreover, lipokinins may be involved as stimulators of the arachidonic acid cascade, as lipocortins are inhibitors.

Lipopolysaccharide alters suckling rat liver glycogenolysis.

Gram-negative sepsis/septic shock in the newborn continues to be a major medical problem, causing high mortality. Hyperglycemia followed by hypoglycemia is a common symptom in endotoxic shock. However, the mechanism of newborn glucoregulatory response to endotoxin has not been well understood. Paradoxically, monocyte-phagocytes can contribute to shock by overwhelming secretion of cytokines and also host defense by detoxifying endotoxin. Since monocyte-phagocyte function is immature in the newborn, this study was performed to evaluate Kupffer cell's role in liver glycogenolysis during endotoxic shock. Endotoxin (LPS) induced hyperglycemia in 10-day-old rats, and increased net glucose output in the isolated perfused liver. 1) Cytarabine decreased Kupffer cell function (decreased hepatic colloid carbon uptake) and blunted LPS-increased liver net glucose output in the Cytarabine + LPS-treated group (104 +/- 4 vs. 146 +/- 3 micrograms/min/g wet liver in the LPS-treated group: P < .001). 2) Indomethacin (IND) suppressed LPS-induced liver net glucose output in the LPS + IND-treated group (133 +/- 5 vs. 146 +/- 3 micrograms/min/g wet liver, P < .05). Thus, prostaglandins were suggested to contribute to glycogenolysis in the 10-day-old rat liver. 3) Phorbol 12-myristate 13-acetate (PMA) increased liver net glucose output (166 +/- 4 micrograms/min/g wet liver), and H-7, a protein kinase C inhibitor, blunted PMA-induced liver glucose output (140 +/- 2 micrograms/min/g wet liver, P < .05). H-7 enhanced LPS-induced liver net glucose output (196 +/- 9 micrograms/min/g wet liver, P < .01). Therefore, protein kinase C may not be the dominant cell signaling system for LPS stimulation in suckling rat Kupffer cells.