Catecholamine-induced release of the folic acid analogue, Methotrexate, from rat hepatocytes in suspension. An alpha-adrenergic phenomenon

D. A. Gewirtz, J. K. Randolph, I. David Goldman

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Studies were undertaken to explore the mechanism(s) for release of the folic acid analogue, methotrexate, from freshly isolated rat hepatocytes in suspension. When cells are at steady state with exchangeable intracellular methotrexate, net efflux of methotrexate is induced by 10 μM epinephrine. This net efflux of methotrexate induced by epinephrine is markedly potentiated by 3-isobutyl-1-methylxanthine at concentrations which do not, alone, result in net loss of methotrexate from the cells. Epinephrine (in the presence of isobutyl methylxanthine) is the most potent of the catecholamines tested in inducing methotrexate efflux; equimolar norepinephrine or phenylephrine are less effective, and isoproterenol is essentially ineffective. This order of potency for the catecholamines suggests an alpha-adrenergic-mediated exit of methotrexate from these cells. This is further supported by the observations that the alpha antagonists phenoxybenzamine and prazosin significantly depress methotrexate efflux induced by epinephrine plus isobutyl methylxanthine, whereas the beta antagonists propranolol and dichloroisoproterenol have no effect on induction of drug exit. Incubation of hepatocytes with the calcium-chelating agent ethylene glycol bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid reduces or eliminates efflux of methotrexate induced by epinephrine or epinephrine plus isobutyl methylxanthine, consistent with calcium involvement in alpha-adrenergic phenomena. Similarly, arginine vasopressin effects methotrexate release by a calcium-dependent mechanism. This calcium-dependent efflux of methotrexate from hepatocytes induced by alpha-adrenergic stimuli in vitro may represent a 'secretory' phenomenon which modulates release of this antifolate into the capillary sinusoid or bile canaliculus when the hepatocyte is in its usual spatial orientation within the liver lobule.

Original languageEnglish (US)
Pages (from-to)493-499
Number of pages7
JournalMolecular Pharmacology
Volume22
Issue number2
StatePublished - 1982
Externally publishedYes

Fingerprint

Folic Acid
Methotrexate
Adrenergic Agents
Catecholamines
Hepatocytes
Suspensions
Epinephrine
Calcium
Bile Canaliculi
Folic Acid Antagonists
1-Methyl-3-isobutylxanthine
Phenoxybenzamine
Ethylene Glycol
Arginine Vasopressin
Prazosin
Phenylephrine
Isoproterenol
Propranolol
Ether
Norepinephrine

ASJC Scopus subject areas

  • Pharmacology

Cite this

Catecholamine-induced release of the folic acid analogue, Methotrexate, from rat hepatocytes in suspension. An alpha-adrenergic phenomenon. / Gewirtz, D. A.; Randolph, J. K.; Goldman, I. David.

In: Molecular Pharmacology, Vol. 22, No. 2, 1982, p. 493-499.

Research output: Contribution to journalArticle

@article{c2b4ef92463040a5b11e81e435f889a1,
title = "Catecholamine-induced release of the folic acid analogue, Methotrexate, from rat hepatocytes in suspension. An alpha-adrenergic phenomenon",
abstract = "Studies were undertaken to explore the mechanism(s) for release of the folic acid analogue, methotrexate, from freshly isolated rat hepatocytes in suspension. When cells are at steady state with exchangeable intracellular methotrexate, net efflux of methotrexate is induced by 10 μM epinephrine. This net efflux of methotrexate induced by epinephrine is markedly potentiated by 3-isobutyl-1-methylxanthine at concentrations which do not, alone, result in net loss of methotrexate from the cells. Epinephrine (in the presence of isobutyl methylxanthine) is the most potent of the catecholamines tested in inducing methotrexate efflux; equimolar norepinephrine or phenylephrine are less effective, and isoproterenol is essentially ineffective. This order of potency for the catecholamines suggests an alpha-adrenergic-mediated exit of methotrexate from these cells. This is further supported by the observations that the alpha antagonists phenoxybenzamine and prazosin significantly depress methotrexate efflux induced by epinephrine plus isobutyl methylxanthine, whereas the beta antagonists propranolol and dichloroisoproterenol have no effect on induction of drug exit. Incubation of hepatocytes with the calcium-chelating agent ethylene glycol bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid reduces or eliminates efflux of methotrexate induced by epinephrine or epinephrine plus isobutyl methylxanthine, consistent with calcium involvement in alpha-adrenergic phenomena. Similarly, arginine vasopressin effects methotrexate release by a calcium-dependent mechanism. This calcium-dependent efflux of methotrexate from hepatocytes induced by alpha-adrenergic stimuli in vitro may represent a 'secretory' phenomenon which modulates release of this antifolate into the capillary sinusoid or bile canaliculus when the hepatocyte is in its usual spatial orientation within the liver lobule.",
author = "Gewirtz, {D. A.} and Randolph, {J. K.} and Goldman, {I. David}",
year = "1982",
language = "English (US)",
volume = "22",
pages = "493--499",
journal = "Molecular Pharmacology",
issn = "0026-895X",
publisher = "American Society for Pharmacology and Experimental Therapeutics",
number = "2",

}

TY - JOUR

T1 - Catecholamine-induced release of the folic acid analogue, Methotrexate, from rat hepatocytes in suspension. An alpha-adrenergic phenomenon

AU - Gewirtz, D. A.

AU - Randolph, J. K.

AU - Goldman, I. David

PY - 1982

Y1 - 1982

N2 - Studies were undertaken to explore the mechanism(s) for release of the folic acid analogue, methotrexate, from freshly isolated rat hepatocytes in suspension. When cells are at steady state with exchangeable intracellular methotrexate, net efflux of methotrexate is induced by 10 μM epinephrine. This net efflux of methotrexate induced by epinephrine is markedly potentiated by 3-isobutyl-1-methylxanthine at concentrations which do not, alone, result in net loss of methotrexate from the cells. Epinephrine (in the presence of isobutyl methylxanthine) is the most potent of the catecholamines tested in inducing methotrexate efflux; equimolar norepinephrine or phenylephrine are less effective, and isoproterenol is essentially ineffective. This order of potency for the catecholamines suggests an alpha-adrenergic-mediated exit of methotrexate from these cells. This is further supported by the observations that the alpha antagonists phenoxybenzamine and prazosin significantly depress methotrexate efflux induced by epinephrine plus isobutyl methylxanthine, whereas the beta antagonists propranolol and dichloroisoproterenol have no effect on induction of drug exit. Incubation of hepatocytes with the calcium-chelating agent ethylene glycol bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid reduces or eliminates efflux of methotrexate induced by epinephrine or epinephrine plus isobutyl methylxanthine, consistent with calcium involvement in alpha-adrenergic phenomena. Similarly, arginine vasopressin effects methotrexate release by a calcium-dependent mechanism. This calcium-dependent efflux of methotrexate from hepatocytes induced by alpha-adrenergic stimuli in vitro may represent a 'secretory' phenomenon which modulates release of this antifolate into the capillary sinusoid or bile canaliculus when the hepatocyte is in its usual spatial orientation within the liver lobule.

AB - Studies were undertaken to explore the mechanism(s) for release of the folic acid analogue, methotrexate, from freshly isolated rat hepatocytes in suspension. When cells are at steady state with exchangeable intracellular methotrexate, net efflux of methotrexate is induced by 10 μM epinephrine. This net efflux of methotrexate induced by epinephrine is markedly potentiated by 3-isobutyl-1-methylxanthine at concentrations which do not, alone, result in net loss of methotrexate from the cells. Epinephrine (in the presence of isobutyl methylxanthine) is the most potent of the catecholamines tested in inducing methotrexate efflux; equimolar norepinephrine or phenylephrine are less effective, and isoproterenol is essentially ineffective. This order of potency for the catecholamines suggests an alpha-adrenergic-mediated exit of methotrexate from these cells. This is further supported by the observations that the alpha antagonists phenoxybenzamine and prazosin significantly depress methotrexate efflux induced by epinephrine plus isobutyl methylxanthine, whereas the beta antagonists propranolol and dichloroisoproterenol have no effect on induction of drug exit. Incubation of hepatocytes with the calcium-chelating agent ethylene glycol bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid reduces or eliminates efflux of methotrexate induced by epinephrine or epinephrine plus isobutyl methylxanthine, consistent with calcium involvement in alpha-adrenergic phenomena. Similarly, arginine vasopressin effects methotrexate release by a calcium-dependent mechanism. This calcium-dependent efflux of methotrexate from hepatocytes induced by alpha-adrenergic stimuli in vitro may represent a 'secretory' phenomenon which modulates release of this antifolate into the capillary sinusoid or bile canaliculus when the hepatocyte is in its usual spatial orientation within the liver lobule.

UR - http://www.scopus.com/inward/record.url?scp=0019964307&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0019964307&partnerID=8YFLogxK

M3 - Article

VL - 22

SP - 493

EP - 499

JO - Molecular Pharmacology

JF - Molecular Pharmacology

SN - 0026-895X

IS - 2

ER -