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In searching for androgen-responsive genes in human prostate cancer cells, we have isolated two cDNAs that encode alternate forms of a novel Src homology 3 domain-containing guanine nucleotide exchange factor (SGEF). The SGEF mRNA is widely expressed in human tissues, and the predicted 871-amino acid SGEF protein contains Dbl homology and pleckstrin homology domains as well as an N-terminal proline-rich domain, a C-terminal Src homology 3 domain, and two nuclear localization signals. The second cDNA encodes a 139-amino acid N-terminally truncated form of SGEF designated C-terminal SGEF (CSGEF). In contrast to SGEF, CSGEF mRNA expression is restricted to prostate and liver. Moreover, CSGEF expression is up-regulated by androgens in LNCaP cells, whereas that of SGEF is not. Up-regulation of CSGEF was sensitive to actinomycin D but did not require new protein synthesis. The SGEF gene is located on chromosome 3q25.2 and consists of at least 15 exons. Based on the structure of the SGEF and CSGEF cDNAs, we deduced that CSGEF expression is controlled by an alternate androgen-responsive promoter of the SGEF gene. We hypothesize that SGEF is a ubiquitous regulator of Rho guanosine triphosphatases, whereas CSGEF may function as an androgen-induced regulator of Rho guanosine triphosphatase activity in epithelial cells of the human prostate.

The presence of arginine vasopressin (AVP)-like peptide(s) and AVP receptors has been previously demonstrated in the testis of several species. In this study we examined the immunocytochemical localization of AVP and of its associated neurophysin (NPII) within the mouse testis, and the testicular immunoreactive (IR)-AVP content in normal pubertal and adult mice and in unilaterally cryptorchid animals. Immunostaining was conducted on fresh frozen adult testicular sections and on cultured testicular cells using the avidin-biotin immunoperoxidase technique. Immunoreactivities for AVP and NPII were localized at the periphery of the seminiferous tubules. Staining for AVP and NPII was reduced in testes showing impaired spermatogenesis. AVP and NPII immunoreactivities were present in cultured Sertoli cells, but staining was undetectable in cultured Leydig cells. Negative controls were obtained by applying antiserum that had been preabsorbed with excess peptides in place of primary antiserum. Mouse testes were found to contain IR-AVP, which co-eluted with synthetic AVP on HPLC and diluted in parallel in a specific RIA for AVP. Levels of IR-AVP expressed as pg/mg wet-weight testis were significantly higher (p < 0.05) in pubertal (36.6 +/- 1.5) than in adult animals (27.4 +/- 1.5). Experimental unilateral cryptorchidism in adult animals resulted 2 wk later in a marked reduction (p < 0.01) in IR-AVP levels in the abdominal testis (18.1 +/- 1.0 pg/mg testis) as compared to the contralateral scrotal testis (29.8 +/- 1.1 pg/mg testis).(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of intratesticular injection of naloxone, a universal opioid antagonist, on testicular immunoreactive (IR)-arginine vasopressin (AVP) content and on in vitro testosterone production by Leydig cells were investigated in the mouse. Bilateral intratesticular injection of increasing doses of naloxone (0.1-10 micrograms/testis) resulted 24 h later in a dose-dependent increase in testosterone production by Leydig cells incubated for 3 h in the presence or absence of hCG (100 ng/ml). Unilateral intratesticular injection of naloxone (10 micrograms) similarly enhanced basal and hCG-stimulated testosterone production by Leydig cells, but production was not modified in Leydig cells from the contralateral vehicle-injected testis, nor was it changed when the same dose was injected subcutaneously. Unilateral intratesticular injection of 10 micrograms naloxone led to a dose-dependent increase in the hCG-responsiveness without altering the slope of the hCG dose-response curve. In vitro exposure of Leydig cells to increasing doses of naloxone (10(-9) to 10(-7) M) did not alter either basal or hCG-stimulated testosterone production. Testicular IR-AVP content declined in a dose-dependent manner in naloxone-injected testis, but remained unchanged in the contralateral vehicle-injected testis and in testis from animals that received similar doses of naloxone subcutaneously. Since AVP has been shown to locally exert a negative control on testosterone production within the testis, it might be hypothesized that the increased Leydig cell activity after local naloxone administration results from reduced intratesticular IR-AVP levels.(ABSTRACT TRUNCATED AT 250 WORDS)