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Studies on the microsoml sodium-plus-potassium ion-stimulated adenosine triphosphatase system in rat ventral prostate
Abstract:
A Mg(2+)+Na(+)+K(+)-stimulated adenosine triphosphatase (ATPase) preparation was isolated from rat ventral prostate by flotation of microsomal membranes in high-density sucrose solutions. The reaction medium for optimum Na(+)+K(+)-stimulated ATPase activity was found to be: Na(+), 115mm; K(+), 7-10mm; Mg(2+), 3mm; ATP, 3mm; tris buffer, pH7.4 at 38 degrees , 20mm. The average DeltaP(i) (Mg(2+)+Na(+)+K(+) minus Mg(2+)+Na(+)) was 9mumoles/mg. of protein/hr., representing a 30% increase over the Mg(2+)+Na(+)-stimulated ATPase activity. At high concentrations, K(+) was inhibitory to the enzyme activity. Half-maximal inhibition of Na(+)+K(+)-stimulated ATPase activity was elicited by ouabain at 0.1mm. The preparation exhibited phosphatase activity towards ribonucleoside triphosphates other than ATP. However, stimulation of P(i) release by Na(+)+K(+) was observed only with ATP as substrate. The apparent K(m) for ATP for Na(+)+K(+)-stimulated activity was about 0.3x10(-3)m. Ca(2+) inhibited only the Na(+)+K(+)-stimulated ATPase activity. Mg(2+) could be replaced by Ca(2+) but then no Na(+)+K(+) stimulation of ATPase activity was noticed. The addition of testosterone or dihydrotestosterone (17beta-hydroxy-5alpha-androstan-3-one) in vitro at 0.1-10mum under a variety of experimental conditions did not significantly increase the Na(+)+K(+)-stimulated ATPase activity. The enzyme preparations from prostates of orchidectomized rats, however, exhibited a drastic decrease in the specific activity of Na(+)+K(+)-stimulated ATPase; these changes were prevented in the orchidectomized rats by injection of testosterone propionate.
Insights
This study isolated a sodium-potassium-stimulated adenosine triphosphatase (Na(+)+K(+)-ATPase) from rat prostate. Enzyme activity was optimized, and its dependence on androgens like testosterone was confirmed, particularly after orchidectomy.
Area of Science:
- Biochemistry
- Enzymology
- Molecular Biology
Background:
- The ventral prostate's function is influenced by androgens.
- Adenosine triphosphatase (ATPase) activity is crucial for cellular processes.
- Understanding Na(+)+K(+)-ATPase in the prostate can reveal androgenic effects.
Purpose of the Study:
- To isolate and characterize Mg(2+)+Na(+)+K(+)-stimulated ATPase from rat ventral prostate.
- To investigate the enzyme's kinetic properties and response to various ions and androgens.
- To determine the role of Na(+)+K(+)-ATPase in androgen-dependent prostate physiology.
Main Methods:
- Microsomal membranes were isolated from rat ventral prostate using sucrose density gradient flotation.
- Na(+)+K(+)-stimulated ATPase activity was assayed under varying ionic conditions and substrate concentrations.
- Enzyme kinetics, inhibition by ouabain and Ca(2+), and effects of testosterone/dihydrotestosterone were evaluated.
Main Results:
- Optimized conditions for Na(+)+K(+)-stimulated ATPase activity were determined (115mm Na(+), 7-10mm K(+), 3mm Mg(2+), 3mm ATP, pH 7.4, 38°C).
- The enzyme showed specific Na(+)+K(+)-stimulated activity, inhibited by high K(+) concentrations and ouabain (0.1mm).
- Testosterone and dihydrotestosterone did not enhance activity in vitro, but orchidectomy drastically reduced Na(+)+K(+)-ATPase activity, which was restored by testosterone propionate.
Conclusions:
- The study successfully isolated and characterized a Na(+)+K(+)-ATPase from rat ventral prostate.
- Prostate Na(+)+K(+)-ATPase activity is significantly regulated by androgens, with testosterone playing a key role.
- This enzyme may be involved in the physiological functions of the prostate modulated by androgens.