title: 11beta-hydroxysteroid dehydrogenase in the testis of Bufo arenarum: changes in its seasonal activity.
abstract: In rat Leydig cells, glucocorticoids (GC) inhibit testosterone (T) synthesis via glucocorticoid receptor (GR). However, GC access to GR is regulated by the local expression of 11beta-hydroxysteroid dehydrogenase (11beta-HSD). Two isoforms were identified in mammals: type 1, a NADP+-preferring enzyme with K(m) in the muM range for GC and type 2, NAD+-dependent, with K(m) in the nM range for GC. In amphibians, a seasonal rhythm in baseline GC levels was described. However, a shift in the amount of deactivating 11beta-HSD activity could alter GC effects. The purpose of this work is to describe seasonal changes in testicular activity of 11beta-HSD in Bufo arenarum as well as the annual and seasonal patterns of plasma corticosterone (B) and T. The activity of 11beta-HSD was assayed in homogenate and subcellular fractions in pre-reproductive (Pre-R), reproductive (R) and post-reproductive (Post-R) periods, using [3H]B. Plasma B and T were determined by RIA. Testicular 11beta-HSD is a microsomal NAD+-dependent enzyme with a K(m) in the nM order, its activity being strongly reduced by glycyrrhetinic acid. These results indicate that toad testes express an 11beta-HSD similar to mammalian type 2. Although 11beta-HSD activity is higher in the Post-R than in the R and Pre-R seasons (V(max): Pre-R: 0.26+/-0.10, R: 0.14+/-0.01, Post-R: 1.37+/-0.45, pmol/minmg protein), K(m) value remains constant throughout the year. A seasonal rhythm in baseline GC concentrations inversely correlated with plasma T was also described. T concentration is lower in the R season than in the other periods (Pre-R: 90+/-6; R: 12+/-1; Post-R: 56+/-3, nM) while total B concentration is higher in the breeding than in the other seasons (Pre-R: 62+/-10; R: 145+/-18; Post-R: 96+/-10, nM). Furthermore, free B (Pre-R: 51+/-8; R: 94+/-12; Post-R: 70+/-7, nM) was always below K(m) values. In conclusion, this work shows that the activity of 11beta-HSD in toad testes could modulate GC action by transforming active hormones in the corresponding inactive steroid.
authors.affiliation: Laboratorio de Endocrinología Comparada and PRHOM-CONICET, Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Daniela
authors.initials: D
authors.lastname: Denari
authors.forename: Nora R
authors.initials: NR
authors.lastname: Ceballos
mesh_terms: D042842:11-beta-Hydroxysteroid Dehydrogenases / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D002022:Bufo arenarum / Q000378:metabolism*; D003345:Corticosterone / Q000097:blood*; D005938:Glucocorticoids / Q000378:metabolism; D008297:Male; D012098:Reproduction / Q000502:physiology; D012621:Seasons; D018709:Statistics, Nonparametric; D013737:Testis / Q000201:enzymology*; D013739:Testosterone / Q000097:blood*
chemical_list: D005938:Glucocorticoids; D013739:Testosterone; D042842:11-beta-Hydroxysteroid Dehydrogenases; D003345:Corticosterone