We have recently demonstrated the expression of leptin and leptin receptor (Ob-R) isoforms a, b, c, e and f in the rat seminal vesicles and prostate. The aim of the present study was to provide a semiquantitative real-time PCR estimation of leptin/Ob-R isoform mRNA expression in the seminal vesicles and individual components of rat prostate, and to ascertain the in vitro effects of leptin on prostate acid phosphatase release. The highest expression of the leptin and Ob-R genes was in the seminal vesicles and lateral prostate lobe, respectively. Of the various isoforms, Ob-Rb displayed the highest and Ob-Re the lowest expression. Leptin (10(-8) and 10(-6) M) enhanced acid phosphate release from seminal vesicles, and (10(-6) M) decreased it from the coagulating lobe. Taken together, our findings support the contention that leptin may be involved in the autocrine-paracrine functional regulation of rat seminal vesicles and prostate. The physiological relevance of the marked heterogeneity of the different prostate lobes in both their leptin/Ob-R expression and functional response to leptin remains to be addressed.