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Liver plasma membrane (LPM) NaK-ATPase activity, LPM fluidity, and bile acid-independent flow (BAIF) were studied in rats pretreated with one of five experimental agents. Compared with controls, BAIF was increased 24.6% by thyroid hormone and 34.4% by phenobarbital, decreased by ethinyl estradiol, but unchanged by propylene glycol and cortisone acetate. Parallel to the observed changes in BAIF, NaK-ATPase activity also was increased by thyroid hormone (40.8%) and decreased by ethinyl estradiol (26.2%). In contrast, NaK-ATPase activity failed to increase after phenobarbital but did increase 36% after propylene glycol and 34.8% after cortisone acetate. Thus BAIF and NaK-ATPase activity did not always change in parallel. The NaK-ATPase K(m) for ATP was not affected by any of these agents.LPM fluidity, measured by fluorescence polarization using the probe 1,6-diphenyl-1,3,5-hexatriene, was found to be increased by propylene glycol, thyroid hormone, and cortisone acetate, decreased by ethinyl estradiol, and unaffected by phenobarbital. Thus in these cases, induced changes in LPM fluidity paralleled those in NaK-ATPase activity. In no case did Mg-ATPase or 5'-nucleotidase activities change in the same direction as NaK-ATPase, and the activity of neither of these enzymes correlated with LPM fluidity, thus indicating the selective nature of the changes in LPM enzyme activity caused by the agents. These findings indicate that LPM fluidity correlates with NaK-ATPase activity and may influence the activity of this enzyme. However, the nature of the role of LPM NaK-ATPase in bile secretion is uncertain and needs further study.
E B Keefee, and
B F Scharschmidt, and
N M Blankenship, and
R K Ockner
February 1978,
The Journal of clinical investigation,
E B Keefee, and
B F Scharschmidt, and
N M Blankenship, and
R K Ockner
January 1998,
Clinical science (London, England : 1979),
E B Keefee, and
B F Scharschmidt, and
N M Blankenship, and
R K Ockner
January 1981,
Hepatology (Baltimore, Md.),
E B Keefee, and
B F Scharschmidt, and
N M Blankenship, and
R K Ockner
May 1987,
The American journal of physiology,
E B Keefee, and
B F Scharschmidt, and
N M Blankenship, and
R K Ockner
January 1977,
Biochemistry and experimental biology,
E B Keefee, and
B F Scharschmidt, and
N M Blankenship, and
R K Ockner
May 1977,
Diabetologia,
E B Keefee, and
B F Scharschmidt, and
N M Blankenship, and
R K Ockner
August 1979,
Biochimica et biophysica acta,
E B Keefee, and
B F Scharschmidt, and
N M Blankenship, and
R K Ockner
January 1983,
Alcoholism, clinical and experimental research,
E B Keefee, and
B F Scharschmidt, and
N M Blankenship, and
R K Ockner
December 2001,
Experimental gerontology,
E B Keefee, and
B F Scharschmidt, and
N M Blankenship, and
R K Ockner
January 1982,
Annals of the New York Academy of Sciences,
