Somatostatin inhibits stem cell factor messenger RNA expression by Sertoli cells and stem cell factor-induced DNA synthesis in isolated seminiferous tubules.
Immature porcine Sertoli cells have been reported to be targets for the regulatory peptide somatostatin (SRIF), which inhibits the basal and FSH-induced proliferation of Sertoli cells through a decrease of cAMP production. In the present study, we show that SRIF inhibits both basal and FSH-stimulated expression of the stem cell factor (SCF), a Sertoli cell-specific gene. The SRIF-mediated inhibition of forskolin-triggered, but not of 8-bromoadenosine-cAMP-triggered, SCF mRNA expression demonstrates the involvement of adenylyl cyclase in underlying peptide actions. Moreover, these effects require functional coupling of specific plasma membrane receptors to adenylyl cyclase via inhibitory G proteins, because pertussis toxin prevents SRIF-mediated inhibition of SCF mRNA expression. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blot assays suggest the involvement of sst2 receptors in SRIF actions on Sertoli cells. The biological relevance of these data is supported by an SRIF-mediated decrease in SCF-induced incorporation of [(3)H]thymidine in isolated seminiferous tubules. In situ hybridization and confocal microscopy show that, in seminiferous tubules only, spermatogonia display both c-kit and sst2 receptors. Taken together, these results suggest that SCF-stimulated DNA synthesis can be inhibited by SRIF in spermatogonia, but not in Sertoli and peritubular cells. Combined RT-PCR and immunohistochemical approaches point toward spermatogonia and Leydig cells as the source of testicular SRIF. These data argue in favor of paracrine/autocrine SRIF actions in testis.
Goddard
I
I
Institut National de la Santé et de la Recherche Médicale (INSERM) Unité 407, Faculté de Médecine Lyon Sud, F-69921 Oullins, France.
Bauer
S
S
Gougeon
A
A
Lopez
F
F
Giannetti
N
N
Susini
C
C
Benahmed
M
M
Krantic
S
S
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D037361:Adenylate Cyclase Toxin; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D005576:Colforsin / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis*; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology; D015870:Gene Expression / Q000187:drug effects*; D017403:In Situ Hybridization; D008297:Male; D018613:Microscopy, Confocal; D037342:Pertussis Toxin; D019009:Proto-Oncogene Proteins c-kit / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D017481:Receptors, Somatostatin / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012671:Seminiferous Tubules / Q000378:metabolism*; D012708:Sertoli Cells / Q000378:metabolism*; D013004:Somatostatin / Q000494:pharmacology*; D013093:Spermatogonia / Q000737:chemistry; D019089:Stem Cell Factor / Q000235:genetics* / Q000494:pharmacology; D013552:Swine; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D012333:RNA, Messenger; D017481:Receptors, Somatostatin; D019089:Stem Cell Factor; D010566:Virulence Factors, Bordetella; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D013004:Somatostatin; D005640:Follicle Stimulating Hormone; D004247:DNA; D037342:Pertussis Toxin; D019009:Proto-Oncogene Proteins c-kit; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases