Androgen interaction with the polyamine system of the rat prostate

The ventral and dorsal lobes of the rat prostate contain larger quantities of the aliphatic amines putrescine, spermidine and spermine and higher activities of the enzyme ornithine decarboxylase (ODC; EC 4.1.1.17) than other accessory sex glands. In contrast, the coagulating glands and the seminal vesicles contain only small quantities of the amines but the highest activities of the arginase (ARG; EC 3.5.3.1). Lineweaver-Burk plots indicated that the Km-values for ARG in the coagulating gland and ODC in the ventral prostate lobe were 20 mM and 0.2 mM, respectively. Castration decreased ODC and ARG activities to 3 and 50% of control levels, respectively, after 3 days, whilst the Km-values were unaffected. Daily administration of 3 mg dihydrotestosterone (DHT) prevented these castrational changes. Oestrogen treatment alone had no effect on the activities of the enzymes, but appeared to exert a synergistic effect with androgen on the ODC. Administration of androgen to intact rats for 7 days caused a dose-related alteration in the ratios of the various amines, particularly the spermine: putrescine ratio. A minor but significant decrease was also recorded in the activity of the ODC, which was mirrored by an increase in the levels of putrescine in the tissue. The data suggest that androgen control of the polyamine pathway is biphasic, first stimulatory and later inhibitory with lesions occurring at the ODC, possibly via short loop feedback of its product putrescine, but also at subsequent enzymic steps in spermidine and spermine biosynthesis.