Document Detail

Endocrine roles of D-aspartic acid in the testis of lizard Podarcis s. sicula.
MedLine Citation:
PMID:  16423814     Owner:  NLM     Status:  MEDLINE    
In the lizard Podarcis s. sicula, a substantial amount of D-aspartate (D-Asp) is endogenous to the testis and shows cyclic changes of activity connected with sex hormone profiles during the annual reproductive phases. Testicular D-Asp content shows a direct correlation with testosterone titres and a reverse correlation with 17beta-estradiol titres. In vivo experiments, consisting of i.p. injections of 2.0 micromol/g body weight of D-Asp or other amino acids, in lizards collected during the three main phases of the reproductive cycle (pre-reproductive, reproductive and post-reproductive period), revealed that the testis can specifically take up and accumulate D-Asp alone. Moreover, this amino acid influences the synthesis of testosterone and 17beta-estradiol in all phases of the cycle. This phenomenon is particularly evident during the pre- and post-reproductive period, when endogenous testosterone levels observed in both testis and plasma were the lowest and 17beta-estradiol concentrations were the highest. D-Asp rapidly induces a fall in 17beta-estradiol and a rise in testosterone at 3 h post-injection in the testis and at 6 h post-injection in the blood. In vitro experiments show that testicular tissue converted L-Asp into D-Asp through an aspartate racemase. D-Asp synthesis was measured in all phases of the cycle, but was significantly higher during the reproductive period with a peak at pH 6.0. The exogenous D-Asp also induces a significant increase in the mitotic activity of the testis at 3 h (P < 0.05) and at 6 h (P < 0.01). Induction of spermatogenesis by D-Asp is recognized by an intense immunoreactivity of the germinal epithelium (spermatogonia and spermatids) for proliferation cell nuclear antigen (PCNA). The effects of D-Asp on the testis appear to be specific since they were not seen in lizards injected with other D- or L-forms of amino acids with known excitatory effects on neurosecretion. Our results suggest a regulatory role for D-Asp in the steroido-genesis and spermatogenesis of the testis of the lizard Podarcis s. sicula.
F Raucci; S D'Aniello; M M Di Fiore
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of endocrinology     Volume:  187     ISSN:  0022-0795     ISO Abbreviation:  J. Endocrinol.     Publication Date:  2005 Dec 
Date Detail:
Created Date:  2006-01-20     Completed Date:  2006-02-09     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0375363     Medline TA:  J Endocrinol     Country:  England    
Other Details:
Languages:  eng     Pagination:  347-59     Citation Subset:  IM    
Department of Life Sciences, Second University of Naples, Via Vivaldi 43, 81100 Caserta, Italy.
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MeSH Terms
Amino Acid Isomerases / metabolism
D-Aspartic Acid / biosynthesis,  physiology*
Estradiol / analysis,  blood
Immunohistochemistry / methods
Lizards / anatomy & histology,  immunology,  physiology*
Proliferating Cell Nuclear Antigen / analysis
Spermatids / immunology
Spermatogenesis / physiology
Spermatogonia / immunology
Testis / anatomy & histology,  immunology,  physiology*
Testosterone / analysis,  blood
Reg. No./Substance:
0/Proliferating Cell Nuclear Antigen; 1783-96-6/D-Aspartic Acid; 50-28-2/Estradiol; 58-22-0/Testosterone; EC 5.1.1.-/Amino Acid Isomerases; EC racemase

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