Involvement of D-Asp in P450 aromatase activity and estrogen receptors in boar testis.
Mammalian testis contains D-aspartic acid (D-Asp), which enhances testosterone production. D-Asp, on other hand, also stimulates 17beta-estradiol synthesis in the ovary of some lower vertebrates. We studied boar testis in order to determine if D-Asp intervenes in 17beta-estradiol synthesis in the testis of those mammals which produce significant amounts of estrogens as well as testosterone. The boar testis contains D-Asp (40 +/- 3.6 nmol/g tissue) which, according to immunohistological techniques, is localized mainly in Leydig cells, and, to a lesser extent, in sustentacular (Sertoli), peritubular and some germ cells. The enzyme P450aromatase is present in Leydig cells and few germ cells. In vitro experiments showed that the addition of D-Asp to testicular tissue extracts induced a significant increase of aromatase activity, as evaluated by testosterone conversion into 17beta-estradiol. The enzyme's K(m) was not affected by D-Asp (about 25 nM in both control and D-Asp added tests). On the basis of these results we suggest that, as in the ovary, D-Asp is involved in the local control of aromatase activity of boar testis and, therefore, it intervenes in the 17beta-estradiol production. In the testis, the D-Asp targets are presumably the Leydig cells, which having also a nuclear estrogen receptor are, in turn, one of the putative targets of the 17beta-estradiol that they produce (autocrine effect).
Lamanna
C
C
Department of Life Sciences, Second University of Naples, Caserta, Italy.
Assisi
L
L
Botte
V
V
Di Fiore
M M
MM
D000818:Animals; D001141:Aromatase / Q000378:metabolism*; D019898:Autocrine Communication / Q000502:physiology; D026603:D-Aspartic Acid / Q000378:metabolism*; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D007985:Leydig Cells / Q000166:cytology / Q000201:enzymology*; D008297:Male; D010053:Ovary / Q000166:cytology / Q000201:enzymology; D011960:Receptors, Estrogen / Q000378:metabolism*; D013739:Testosterone / Q000378:metabolism*
D011960:Receptors, Estrogen; D013739:Testosterone; D026603:D-Aspartic Acid; D004958:Estradiol; D001141:Aromatase