Ca(2+)-dependent and Ca(2+)-independent NO-synthesizing activities of human primordial placenta.

Z. Kukor, M. Tóth

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

In order to localize the site of production of nitrogen monoxide (NO) in first trimester human pregnancy, the cytosol and microsome fractions prepared from homogenized primordial placentas were tested for NO-synthase (NOS) activities by measuring the NADPH-dependent conversion of [3H]arginine to [3H]citrulline. Our results demonstrate that Ca(2+)-dependent enzyme activities are present in both fractions, whereas microsomes exhibit significant Ca(2+)-independent enzyme activity too. The highest specific activity is measurable in the presence of Ca2+ with microsomes, this activity is about 2-fold higher than the Ca(2+)-dependent specific activity of the cytosol. The Ca(2+)-independent specific NOS activity is about 30% of the Ca(2+)-dependent microsomal activity. The microsomal Ca(2+)-dependent NOS activity is inhibited by 50% in the presence of 0.5 mM aminoguanidine (AG), whereas the Ca(2+)-independent activity does not respond to this concentration of AG, suggesting that it is not the inducible isoform of NOS. Our results indicate that (I) NOS activity is present from an early phase of placental development, (II) the NOS activity is of trophoblastic origin, since the primordial placenta is avascular and (III) NO-production by the primordial placenta can proceed in the absence of any Ca(2+)-mobilizing agonist.

Original languageEnglish
Pages (from-to)313-319
Number of pages7
JournalActa Physiologica Hungarica
Volume82
Issue number4
Publication statusPublished - 1994

Fingerprint

Human Activities
Nitric Oxide Synthase
Placenta
Nitric Oxide
Microsomes
Cytosol
Placentation
Citrulline
Enzymes
First Pregnancy Trimester
NADP
Arginine
Protein Isoforms
pimagedine

ASJC Scopus subject areas

  • Physiology

Cite this

Ca(2+)-dependent and Ca(2+)-independent NO-synthesizing activities of human primordial placenta. / Kukor, Z.; Tóth, M.

In: Acta Physiologica Hungarica, Vol. 82, No. 4, 1994, p. 313-319.

Research output: Contribution to journalArticle

@article{237a3e1fcad347eaab0e5429b8352850,
title = "Ca(2+)-dependent and Ca(2+)-independent NO-synthesizing activities of human primordial placenta.",
abstract = "In order to localize the site of production of nitrogen monoxide (NO) in first trimester human pregnancy, the cytosol and microsome fractions prepared from homogenized primordial placentas were tested for NO-synthase (NOS) activities by measuring the NADPH-dependent conversion of [3H]arginine to [3H]citrulline. Our results demonstrate that Ca(2+)-dependent enzyme activities are present in both fractions, whereas microsomes exhibit significant Ca(2+)-independent enzyme activity too. The highest specific activity is measurable in the presence of Ca2+ with microsomes, this activity is about 2-fold higher than the Ca(2+)-dependent specific activity of the cytosol. The Ca(2+)-independent specific NOS activity is about 30{\%} of the Ca(2+)-dependent microsomal activity. The microsomal Ca(2+)-dependent NOS activity is inhibited by 50{\%} in the presence of 0.5 mM aminoguanidine (AG), whereas the Ca(2+)-independent activity does not respond to this concentration of AG, suggesting that it is not the inducible isoform of NOS. Our results indicate that (I) NOS activity is present from an early phase of placental development, (II) the NOS activity is of trophoblastic origin, since the primordial placenta is avascular and (III) NO-production by the primordial placenta can proceed in the absence of any Ca(2+)-mobilizing agonist.",
author = "Z. Kukor and M. T{\'o}th",
year = "1994",
language = "English",
volume = "82",
pages = "313--319",
journal = "Physiology International",
issn = "2498-602X",
publisher = "Akademiai Kiado",
number = "4",

}

TY - JOUR

T1 - Ca(2+)-dependent and Ca(2+)-independent NO-synthesizing activities of human primordial placenta.

AU - Kukor, Z.

AU - Tóth, M.

PY - 1994

Y1 - 1994

N2 - In order to localize the site of production of nitrogen monoxide (NO) in first trimester human pregnancy, the cytosol and microsome fractions prepared from homogenized primordial placentas were tested for NO-synthase (NOS) activities by measuring the NADPH-dependent conversion of [3H]arginine to [3H]citrulline. Our results demonstrate that Ca(2+)-dependent enzyme activities are present in both fractions, whereas microsomes exhibit significant Ca(2+)-independent enzyme activity too. The highest specific activity is measurable in the presence of Ca2+ with microsomes, this activity is about 2-fold higher than the Ca(2+)-dependent specific activity of the cytosol. The Ca(2+)-independent specific NOS activity is about 30% of the Ca(2+)-dependent microsomal activity. The microsomal Ca(2+)-dependent NOS activity is inhibited by 50% in the presence of 0.5 mM aminoguanidine (AG), whereas the Ca(2+)-independent activity does not respond to this concentration of AG, suggesting that it is not the inducible isoform of NOS. Our results indicate that (I) NOS activity is present from an early phase of placental development, (II) the NOS activity is of trophoblastic origin, since the primordial placenta is avascular and (III) NO-production by the primordial placenta can proceed in the absence of any Ca(2+)-mobilizing agonist.

AB - In order to localize the site of production of nitrogen monoxide (NO) in first trimester human pregnancy, the cytosol and microsome fractions prepared from homogenized primordial placentas were tested for NO-synthase (NOS) activities by measuring the NADPH-dependent conversion of [3H]arginine to [3H]citrulline. Our results demonstrate that Ca(2+)-dependent enzyme activities are present in both fractions, whereas microsomes exhibit significant Ca(2+)-independent enzyme activity too. The highest specific activity is measurable in the presence of Ca2+ with microsomes, this activity is about 2-fold higher than the Ca(2+)-dependent specific activity of the cytosol. The Ca(2+)-independent specific NOS activity is about 30% of the Ca(2+)-dependent microsomal activity. The microsomal Ca(2+)-dependent NOS activity is inhibited by 50% in the presence of 0.5 mM aminoguanidine (AG), whereas the Ca(2+)-independent activity does not respond to this concentration of AG, suggesting that it is not the inducible isoform of NOS. Our results indicate that (I) NOS activity is present from an early phase of placental development, (II) the NOS activity is of trophoblastic origin, since the primordial placenta is avascular and (III) NO-production by the primordial placenta can proceed in the absence of any Ca(2+)-mobilizing agonist.

UR - http://www.scopus.com/inward/record.url?scp=0028685449&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0028685449&partnerID=8YFLogxK

M3 - Article

VL - 82

SP - 313

EP - 319

JO - Physiology International

JF - Physiology International

SN - 2498-602X

IS - 4

ER -