CHARACTERIZATION OF UPTAKE OF STEROID GLUCURONIDES INTO ISOLATED MALE AND FEMALE RAT HEPATOCYTES

  • 1 January 1984
    • journal article
    • research article
    • Vol. 229  (1) , 175-181
Abstract
The uptake of estradiol-17.beta.(.beta.-D-glucuronide) (E217G), estriol-16.alpha.(.beta.-D-glucuronide (E316G)), estradiol-17.beta.-3-(.beta.-D-glucuronide) (E23G) and taurocholate (TC) into hepatocytes isolated from male and female rats was examined and was linear for at least 75 s and exhibited Michaelis-Menten kinetics. The Vmax (nm/min per mg of protein) for uptake in female rat hepatocytes ranged from 0.56 for TC to 2.32 for E316G and from 0.89 for TC to 1.62 for E217G in males. For TC, E217G and E23G, the Vmax for uptake was the same or higher in males, whereas for E316G the Vmax was .apprx. 2-fold higher in females. The Km for TC was approximately equal in males and females, whereas for E217G and E316G, males exhibited a 3- to 9-fold lower Km. The rate of uptake of E217G (100 .mu.M) was decreased in the presence of carbonylcyanide-m-chlorophenylhydrazone (23%), 2,4-dinitrophenol (54%), potassium cyanide (38%), iodoacetic acid (46%) and rotenone (50%) and was reduced by 30-40% when Na was replaced with Li or choline or in the presence of ouabain. The rate of uptake of all the organic anions was reduced by 80-85% at 0.degree.-4.degree. C and the cell/medium concentration ratios at 75 s (37.degree. C) exceeded 1. The steroid glucuronides are taken up by the hepatocyte by a saturable process; E217G uptake was partially dependent on metabolic energy and an intact Na gradient. Substrate-dependent differences in the rate of uptake between male and female rat hepatocytes were also seen.

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