Characterization of the mechanisms involved in the gender differences in hepatic taurocholate uptake

Francis R. Simon, John Fortune, Mieko Iwahashi, Susan Bowman, Allan Wolkoff, Eileen Sutherland

Research output: Contribution to journalArticle

48 Scopus citations

Abstract

Gender differences in the hepatic transport of organic anions is well established. Although uptake of many organic anions is greater in females, sodium-dependent taurocholate uptake is greater in hepatocytes from male rats. We examined the hypothesis that endogenous estrogens alter the number of sinusoidal bile acid transporters and/or decrease membrane lipid fluidity. The initial sodium-dependent uptake of [3H]taurocholate was 75% greater in hepatocytes from males than from either intact or oophorectomized females rats. Taurocholate maximal uptake was increased twofold (P < 0.03) without a significant change in the Michaelis-Menten constant. Sinusoidal membrane fractions were isolated from male and female rat livers with equal specific activities and enrichments of Na+-K+-ATPase. Males had a significant (P < 0.05) increase in cholesterol esters and phosphatidylethanolamine-to- phosphatidylcholine ratio. Fluorescence polarization indicated decreased lipid fluidity in females. In females, expression of the sodium-dependent taurocholate peptide (Ntcp) and mRNA were selectively decreased to 46 ± 9 and 54 ± 4% (P < 0.01), respectively, and the organic anion transporter peptide (Oatp) and Na+-K+-ATPase α-subunit were not significantly different. Nuclear run-on analysis indicated a 47% (P < 0.05) decrease in Ntcp transcription, without a significant change in Oatp. In conclusion, these studies demonstrated that decreased sodium-dependent bile salt uptake in female hepatocytes was due to decreased membrane lipid fluidity and a selective decrease in Ntcp.

Original languageEnglish (US)
Pages (from-to)G556-G565
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume276
Issue number2 39-2
DOIs
StatePublished - Feb 1999

Keywords

  • Lipid composition
  • Lipid fluidity
  • Organic anion transport peptide
  • Sodium-dependent taurocholate transporter
  • Transcription

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)

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