Suppressive action of pituitary adenylate cyclase activating polypeptide (PACAP) on proliferation of immature mouse Leydig cell line TM3 cells

Abstract

We aimed in the current study to understand the participation of PACAP in stage-specific Leydig and Sertoli cell functions. For this purpose, clonal cell lines TM3 (Leydig) and TM4 (Sertoli) cells, derived from the testis of immature BALB/c mice, were used. PACAP-specific receptors were detected in TM3 cells, but not in TM4 cells, which were characterized as PAC1 (type I) receptors. Stimulation of cAMP accumulation and testosterone secretion were observed in TM3 cells during 1-2 h treatment with PACAP38 (10(-10)-10(-7) M) or PACAP27 (10(-11)-10(-7) M). After around 10 h treatment with 10(-11)-10(-7) M PACAP38 or PACAP27, proliferation of TM3 cells was suppressed in time- and dose-dependent manners, which was confirmed by real-time cell electronic sensing (RT-CES) system and phase-contrast microscopy. At 6 h after the addition of PACAP38, the percent cell population in G(2)/M phases increased significantly, while that in S phase showed significant decrease with little change in G(0)/G(1) phases. The results revealed that PACAP exerts, in addition to early stimulatory effect on cAMP formation-steroidogenesis, sustained suppressive effect on cell proliferation in TM3 cells by controlling progression of the cell cycle. The suppressive action of PACAP on proliferation in TM3 cells supports the stage-specific participation of the peptide in differentiation of immature mouse Leydig cells.