title: Arginine vasopressin as an intragonadal hormone in Brattleboro rats: presence of a testicular vasopressin-like peptide and functional vasopressin receptors.
abstract: We have previously demonstrated the presence of an arginine vasopressin (AVP)-like peptide and AVP receptors in rat testis. We have also shown a direct inhibitory effect of AVP on androgen biosynthesis by cultured testicular cells. This study examined the presence of testicular AVP-like peptides and AVP receptors in homozygous (di/di) Brattleboro rats, a genetic mutant known to be deficient in hypothalamic, pituitary, and circulating AVP. The supernatant of homogenized 0.1 N acetic acid-extracted testis from adult homozygous Brattleboro rats was chromatographed on a Sephadex G-25 column. The elution profile of AVP immunoreactivity, as measured by a specific RIA, showed three distinct peaks. The first peak eluted close to the column void volume, a second peak eluted at the column total volume, while a third peak coeluted with synthetic AVP. The third peak of immunoreactive material (375 pg/g tissue) behaved similarly to authentic AVP on octadecylsilica adsorption chromatography, showed a competition curve parallel to that of AVP in the RIA, and comigrated with AVP on Sephadex G-25 and reverse phase TLC. The first, but not the second, immunoreactive peak contained enzyme activity that degraded labeled AVP in a time-dependent manner. Additional studies investigated the presence of AVP receptors in testes from Brattleboro rats. Saturable and specific [3H]AVP-binding sites were present in an enriched testicular interstitial cell preparation from these animals. Scatchard analysis indicated a Kd of 5.6 X 10(-10) M and a binding capacity of 9.7 fmol AVP bound/10(6) cells. These receptors were of the vasopressor (V1) subtype, as indicated by the potencies of selective AVP analogs for competition of [3H]AVP binding. The functionality of these receptors was shown by AVP inhibition of gonadotropin-induced androgen biosynthesis in cultured testicular cells derived from Brattleboro rats. Thus, testes from Brattleboro rats contain a high amount of an AVP-like peptide even though these animals lack hypothalamic, pituitary, and circulating AVP. Also, an AVP-degrading enzyme and AVP receptors with a Kd and binding capacity similar to those of Sprague-Dawley rats are present in the testes of Brattleboro rats. These findings add further support to the hypothesis that locally produced AVP acts as an intratesticular modulator of androgen biosynthesis.
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000032:analysis* / Q000378:metabolism / Q000494:pharmacology; D002845:Chromatography; D002855:Chromatography, Thin Layer; D010450:Endopeptidases / Q000378:metabolism; D007986:Luteinizing Hormone / Q000494:pharmacology; D008297:Male; D011374:Progesterone / Q000096:biosynthesis; D011863:Radioimmunoassay; D051381:Rats; D011910:Rats, Brattleboro; D011919:Rats, Inbred Strains; D011945:Receptors, Angiotensin / Q000032:analysis* / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000032:analysis*; D017483:Receptors, Vasopressin; D013737:Testis / Q000032:analysis* / Q000187:drug effects / Q000378:metabolism; D013739:Testosterone / Q000096:biosynthesis
chemical_list: D011945:Receptors, Angiotensin; D011956:Receptors, Cell Surface; D017483:Receptors, Vasopressin; D001127:Arginine Vasopressin; D013739:Testosterone; D011374:Progesterone; D007986:Luteinizing Hormone; D010450:Endopeptidases