The effect of 17α-ethinyl-substituted steroids on adenosine triphosphatases of rat liver plasma membrane

Abstract

In a previous paper (Heikel & Lathe, 1970) it was shown that 17a-ethinyl-substituted oestrogens greatly decreased the bile flow of rats, whereas the parent compound oestradiol-17f had little effect. 19-Nortestosterone had no effect on bile flow and its 17a-ethinyl derivative was inhibitory, but only at much greater doses than oestrogens.

The effect of thyroid hormone on bile salt-independent bile flow and Na+, K+ -ATPase activity in liver plasma membranes enriched in bile canaliculi.

“…Nevertheless, cardiac glycosides inhibit the enzyme in canalicular-enriched LPM fractions in concentrations required to inhibit BSIF in the isolated perfused rat liver (16); temperature dependence of bile flow in this system and LPM Na', K+-ATPase are also identical (16); substitution of sodium for lithium in the perfusate of the isolated perfused rat liver is associated with an impairment in bile secretion (39); several drugs and hormones such as ethynylestradiol (40,41), rose bengal (42,43) and icterogenin (44), have inhibitory effects on both BSIF in vivo, and LPM ATPase activities in vitro; and chronic ethanol administration, which is associated with enhanced BSIF (45), also stimulates Na+, K+-ATPase in liver slices in rats (46). All of these findings are consistent with a role for Na+, K+-ATPase in the regulation of BSIF.…”

“…Canalicular bile production was significantly increased in hyperthyroid rats (3.19±0.23 Al/min per g liver) compared to controls (2.27±0.24 ul/min per g liver), while it diminished in hypothyroid animals (1.58±0.17 Al/min per g liver). Although bile salt excretion was also increased in hyperthyroid animals (62.4±13.3 vs. 41.2±8.4 nmol/min per g liver), the stimulation in canalicular secretion was primarily related to enhancement of the bile salt-independent fraction of flow (2.47 Al/min per g liver in hyperthyroid rats vs. 1.67 /Al/min per g liver in controls). LPM Na', K'-ATPase activity doubled in hyperthyroid animals (21.5±5.8 vs. 10.7±3.1 Amol Pi/mg protein per h) while Mg++-ATPase activity remained unchanged and 5'-nucleotidase activity increased to a small but significant extent.…”

Relationship between bile flow and Na+, K+-adenosinetriphosphatase in liver plasma membranes enriched in bile canaliculi.

“…Several drugs and hormones, such as ethinyl estradiol (5,27), rose bengal (23,28), and icterogenin (29) (23,30,31). Some of these discrepancies may be due to differences in methodology.…”

Inhibition of Adenosine Triphosphatase Activity of the Plasma Membrane Fraction of Oat Roots by Diethylstilbestrol

“…Because ATPase enzymes are believed to be involved with ion transport across the plasma membrane (14), we have investigated the effects of DES on the ATPase activity of the plasma membrane fraction of oat roots. Previous work showed that I0-4 M DES inhibited the ATPase of oat roots about 50% (1); transport ATPases of animal cells were also inhibited by DES (13,20,23).In this paper we report experiments designed to characterize the DES inhibition of the ATPase activity of the plasma membrane fraction from oat roots. We show that DES decreased the Mg2_-, ' (Mg2++K+)-, and AK+-ATPase activities of the plasma membrane fraction.…”

“…Because ATPase enzymes are believed to be involved with ion transport across the plasma membrane (14), we have investigated the effects of DES on the ATPase activity of the plasma membrane fraction of oat roots. Previous work showed that I0-4 M DES inhibited the ATPase of oat roots about 50% (1); transport ATPases of animal cells were also inhibited by DES (13,20,23).…”