A Novel Hypothalamic Peptide, Pituitary Adenylate Cyclase Activating Peptide, Modulates Sertoli Cell Function in Vitro

Abstract

Pituitary adenylate cyclase-activating peptide (PACAP), a novel hypothalamic peptide that has been shown to exist in several tissues including the testis, was examined for its effects on cultured rat Sertoli cells. PACAP stimulates cAMP accumulation in Sertoli cells cultured from 15-day-old rats in the presence or absence of methylisobutylxanthine, a phosphodiesterase inhibitor, and in the presence of pertussis toxin, a blocker of the adenylate cyclase inhibitory pathway. Maximal stimulation, which is 20-40% of that attainable with FSH, occurs at PACAP concentrations of 10 nM: the ED50 is approximately 100 pM. The ability of PACAP to stimulate Sertoli cell cAMP declines with increasing age of donor animals (15-60 days of age) in a fashion similar to the FSH effect. PACAP stimulation of Sertoli cell cAMP accumulation is additive with submaximal, but not maximal, concentrations of FSH or forskolin. PACAP also stimulates the secretion of lactate, estradiol, and inhibin in a concentration-dependent manner. The stimulation of Sertoli cell cAMP accumulation by PACAP is not altered by a vasoactive intestinal peptide antagonist, and vasoactive intestinal peptide alone does not stimulate cAMP accumulation, indicating that PACAP is not acting via vasoactive intestinal peptide receptors. Further experiments are needed to determine whether PACAP is synthesized within the testis and if so, in which cell types; however, the present data clearly demonstrate that PACAP can modulate Sertoli cell function in vitro.

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

“…Autoradiographic evidence demonstrated the presence of type I PACAP27 binding sites on germinal cells in the rat testis (29), while other data showing that PACAP acts through VPAC receptors in the rat testis were also presented (17). Heindel et al mentioned the existence of PACAP receptors on cultured rat (age 14~60 day-old) Sertoli cells (12). We clearly showed the presence of PAC1 PACAP receptors on TM3 cells and not on TM4 cells, supporting possible role of PACAP on Leydig cells, but not on Sertoli cells, of the mouse specifically in immature stage.…”

Pituitary Adenylate Cyclase-Activating Polypeptide and Its Receptors: 20 Years after the Discovery

“…In the human and rat placenta, PAC1-R mRNA colocalizes with PACAP mRNA, and the two transcripts exhibit the same kinetics of expression throughout pregnancy (Koh et al, 2003(Koh et al, , 2005. In the testis, type I PACAP binding sites are found in germ cells (Shivers et al, 1991), Leydig cells (Romanelli et al, 1997), and Sertoli cells (Heindel et al, 1992;Daniel et al, 2001). In situ hybridization and Northern blot analyses indicate that PAC1-R and VPAC2-R mRNAs, but not VPAC1-R mRNA, are expressed in germ cells (Usdin et al, 1994;Krempels et al, 1995;El-Gehani et al, 1998a,b;Koh and Won, 2006).…”

“…The effects of PACAP on protein synthesis in spermatocytes and spermatids are both mimicked by dibutyryl cAMP (West et al, 1995). In cultured Sertoli cells, PACAP increases cAMP concentration and stimulates estradiol and inhibin secretion (Heindel et al, 1992). In the epididymal epithelium, PACAP stimulates chloride secretion, which is important for sperm activation and storage (Zhou et al, 1997).…”

Delayed testicular aging in pituitary adenylate cyclase-activating peptide (PACAP) null mice

“…Indeed, in cultured Leydig cells from both adult and fetal rat, PACAP induces stimulation of cAMP and testosterone secretion (20)(21)(22), showing that, in vitro, it exerts a direct effect on maturation and function of these cells. Furthermore, PACAP stimulates primordial germ cell proliferation in vitro (23) and induces the secretion of lactate and inhibin by Sertoli cells (24).…”