Abstract
Some characteristics of the prostatic ACP of the rat were examined in the crude extract of each ventral and dorsal lobe using p-nitrophenyl phosphate (p-NPP) 2Na as the substrate. The Km was 1.24mM in both lobes and the optimum pH was 4.8. The optimum conditions for the measurement of the enzyme activity were more than 124mM for the substrate concentration, pH 4.8, 1-4mg/ml homogenate and within 30 min for the reaction. One hundred and thirty mM of p-NPP 2Na was ap-plicable since there were negligible spontaneous hydrolysis and no inhibition of the enzyme at this concentration. The comparison of the ACP activities at 5.5mM substrate concentration, which is widely accepted for clinical purpose, and at 130mM, which is equivalent to the concentration of more than 100 times of the Km, revealed that the enzyme activity might be underestimated in case of 5.5mM.
This method was applied to detect the changes of the rat prostatic ACP activity in the ventral and dorsal lobes with age. The activity was relatively low at immature stage and increased with age in both lobes. Weekly increment and tissue levels of the ACP activity showed a peak at puberty, i.e., 6-9 weeks of age, which coincided with a peak of the prostatic weight increment. Peaks of the incre-ment of the weight and enzyme activity, and the tissue levels of the ACP appeared a little later in the dorsal lobe than in the ventral one.
These results clearly indicate that the ACP activity in the ventral and dorsal prostate of the rat culminates at puberty as seen in other species, suggesting a positive correlation to increased tissue levels of androgens.
