Neuropeptide Y and nitrite levels in preeclamptic and normotensive gravid women.

OBJECTIVES: Vascular tone is controlled largely by the sympathetic nervous system and is modulated by neuropeptide Y. Preeclampsia is linked to sympathetic overactivity. Nitric oxide can cause vasorelaxation of vessels or decrease sympathetic outflow by activating the baroreceptor reflex. Our purpose in this study was to compare serum levels of neuropeptide Y and nitrite levels in normotensive and preeclamptic gravid women. STUDY DESIGN: Twelve preeclamptic and 12 normotensive women matched for race, body mass index, parity, and gestational age were studied. Neuropeptide Y was measured by using a commercial radioimmunoassay. Nitric oxide was converted to nitrite by using metallic cadmium, and nitrite levels were determined spectrophotometrically by using a colorimetric assay. Data are presented as mean +/- SEM and were compared by using a t test. RESULTS: Neuropeptide Y levels were similar among preeclamptic and normotensive gravid women (33.8 +/- 3.0 and 32.2 +/- 3 pg/mL, respectively). Similarly, there were no differences in nitrite concentrations between preeclamptic and normotensive patients (11.6 +/- 0.8 vs 11.2 +/- 0.4 micromol/L, respectively). We also examined the ratios of neuropeptide Y and nitrite and found no correlation between preeclamptic and normotensive women. CONCLUSION: Peripheral levels of neuropeptide Y or nitrite do not correlate with preeclampsia. Assessment of sympathetic overactivity in preeclampsia requires an alternate model.

Regulation of hsp70 mRNA levels during oocyte maturation and zygotic gene activation in the mouse.

Protein phosphorylation catalyzed by the cAMP-dependent protein kinase is implicated in transcriptional activation of the embryonic genome in the two-cell mouse embryo, while heat shock protein (hsp70) has been identified as one of the first products of zygotic gene activation. Using reverse transcription-polymerase chain reaction we have analyzed relative changes in the amount of hsp70 mRNA during oocyte maturation and early embryogenesis. We report that the amount of hsp70 mRNA decreases after germinal vesicle breakdown, while inhibiting germinal vesicle breakdown inhibits this maturation-associated decrease. The amount of hsp70 mRNA increases between the one- and two-cell stages. This increase is inhibited by either alpha-amanitin or the cAMP-dependent protein kinase inhibitor H-8; the same concentration of H-7, which is a more potent inhibitor of protein kinase C, has little inhibitory effect on this increase in the relative amount of hsp70 mRNA. Last, addition of cycloheximide to one-cell embryos late in G2 inhibits neither cleavage to the two-cell stage nor the increase in the relative amount of hsp70 mRNA. These results strengthen the previous proposal that protein phosphorylation is involved in zygotic gene activation in the two-cell mouse embryo.

Blastocoel expansion in the preimplantation mouse embryo: stimulation of sodium uptake by cAMP and possible involvement of cAMP-dependent protein kinase.

Elevating cAMP levels in mouse blastocysts increases the rate of blastocoel expansion (F. Manejwala, E. Kaji, and R. M. Schultz, 1986, Cell, 46, 95-103), which requires extracellular sodium (F. Manejwala, E. J. Crago, Jr., and R. M. Schultz, 1989, Dev. Biol. 133, 210-220). We report that cAMP analogs that can activate the cAMP-dependent protein kinase stimulate 22Na+ uptake by cavitating mouse blastocysts and that inhibitors of cAMP-dependent protein kinase activity inhibit the cAMP-stimulated increase in both the rate of blastocoel expansion and 22Na+ uptake.

Blastocoel expansion in the preimplantation mouse embryo: role of extracellular sodium and chloride and possible apical routes of their entry.

The trophectoderm of the mouse blastocyst is a fluid transporting epithelium that is responsible for generating a fluid-filled cavity called the blastocoel. Vectorial transport of ions from the medium into the blastocoel generates an osmotic gradient that drives fluid across this epithelium. We report here that substitution of Na+ or Cl-, but not K+, in the medium halves the rate of blastocoel expansion in the mouse blastocyst. Entrance of Na+ into the trophectoderm may involve several routes, since both blastocoel expansion and 22Na+ uptake are decreased in the presence of the highly specific Na+/H+ exchanger inhibitor, 5-(N-ethyl-N-isopropyl)amiloride, and to a lesser extent with the amiloride-sensitive Na+-channel blocker, benzamil. Uptake of 22Na+ manifests saturation kinetics as a function of extracellular Na+ concentration, whereas uptake of 36Cl- is linear. Furthermore, neither 4,4-diisothiocyanostilbene-2,2-disulfonic acid, which is an inhibitor of the Cl-/HCO3- exchanger, nor 2-(3,4-dichlorobenzyl)-5-nitrobenzoic acid, which is a Cl- -channel blocker, affect either blastocoel expansion or 36Cl- uptake. These results suggest that Na+ entry into the mouse blastocyst is carrier-mediated and probably involves several routes that include the Na+/H+ exchanger and possibly the Na+-channel. Chloride entry, however, may not be carrier-mediated and may occur through a paracellular route, i.e., between the trophectodermal cells.

Development of activatable adenylate cyclase in the preimplantation mouse embryo and a role for cyclic AMP in blastocoel formation.

Forskolin- and cholera toxin-activated adenylate cyclase activity increases between the morula and blastocyst stages of mouse preimplantation development, as assessed by the ability of these agents to increase embryonic cAMP levels. Development of activatable adenylate cyclase requires transcription but is independent of the fifth nuclear replication, cell division, and compaction. Early cavitating embryos treated with cholera toxin and forskolin or with N6-monobutyryl-cAMP display an increase in the rate of fluid accumulation in comparison with untreated controls. The stimulatory effect is specific for cAMP, since neither the inactive cAMP analogue N6-monobutyryl-2'-deoxy-cAMP nor N2-monobutyryl-cGMP stimulates the rate of fluid accumulation. These results constitute the first report of a possible physiological function for cAMP in preimplantation development, namely, in blastocoel formation.