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Titolo:
Evidence for two-cell model of steroidogenesis in four species of amphibian
Autore:
Ahn, RS; Yoo, MS; Kwon, HB;
Indirizzi:
Chonnam Natl Univ, Hormone Res Ctr, Kwangju 500757, South Korea Chonnam Natl Univ Kwangju South Korea 500757 Kwangju 500757, South Korea Chonnam Natl Univ, Dept Biol, Kwangju 500757, South Korea Chonnam Natl Univ Kwangju South Korea 500757 Kwangju 500757, South Korea
Titolo Testata:
JOURNAL OF EXPERIMENTAL ZOOLOGY
fascicolo: 1, volume: 284, anno: 1999,
pagine: 91 - 99
SICI:
0022-104X(19990615)284:1<91:EFTMOS>2.0.ZU;2-W
Fonte:
ISI
Lingua:
ENG
Soggetto:
DIFFERENT DEVELOPMENTAL STAGES; SALMON ONCORHYNCHUS-RHODURUS; OVARIAN FOLLICLES; RANA-NIGROMACULATA; STEROID-PRODUCTION; OOCYTE MATURATION; FOLLICULAR STEROIDOGENESIS; PROGESTERONE PRODUCTION; PREOVULATORY FOLLICLES; GRANULOSA LAYERS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Agriculture,Biology & Environmental Sciences
Life Sciences
Citazioni:
27
Recensione:
Indirizzi per estratti:
Indirizzo: Kwon, HB Chonnam Natl Univ, Hormone Res Ctr, Kwangju 500757, South Korea Chonnam Natl Univ Kwangju South Korea 500757 00757, South Korea
Citazione:
R.S. Ahn et al., "Evidence for two-cell model of steroidogenesis in four species of amphibian", J EXP ZOOL, 284(1), 1999, pp. 91-99

Abstract

Previously, based on studies conducted using Rana nigromaculata, a two-cell model involving the theca and granulosa cells was proposed to account forthe steroidogenic activity of amphibian ovarian follicles. Experiments were carried out to ascertain whether the model was applicable to four other frog species with different reproductive cycles (R. dybowskii, R. rugosa, R.catesbeiana, and Bombina orientalis). Ovarian follicles were collected from each species and manually microdissected to obtain various follicular components: theca-epithelium (THEP) and granulosa cell-enclosed oocyte (GCEO). Subsequent to collection, equal numbers of intact follicles and various follicular components were cultured for 6 hr in the presence of known inducers of steroidogenesis (frog pituitary homogenate [FPH] or 3-iso-butyl-1-methylxanthine [IBMX] + forskolin) or various steroids that serve as substratesfor specific steroidogenic enzymes. Following incubation, culture medium was collected and analyzed by radioimmunoassay (RIA). Both FPH and IBMX + forskolin consistently stimulated secretion of androstenedione (AD), testosterone (T), and estradiol (E-2) from intact follicles obtained from all four frog species. Additionally, in R. dybowskii, these treatments stimulated secretion of progesterone (P-4) and 17 alpha-hydroxyprogesterone (17 alpha-OHP4) into the culture medium. Intact follicles obtained from all species readily converted pregnenolone (P-5), P-4, and 17 alpha-OHP4 to AD, T, and E-2. In contrast GCEO converted P-5, P-4, and 17 alpha-OHP4 to AD and E-2, butnot to T. However, AD, but not P-5, P-4, or 17 alpha-OHP4, was converted to T when cultured in the presence of isolated THEP. The microdissection procedure was also modified to isolate THEP without contaminating granulosa cells. The steroidogenic capacities of "impure" THEP and "pure" theca-epithelium (P-THEP) were then compared. Basal amounts of Pq Were produced when Pg was added to P-THEP, whereas significantly higher amounts were produced in the presence of impure THEP. No significant conversion of P-5 or P-4 to 17 alpha-OHP4 occurred following culture with pure or impure THEP layer. Results suggest that the enzyme activity necessary to metabolize AD --> T is localized in the THEP, whereas the metabolic capacities to convert P-5 --> AD and T --> E-2 are present in the granulosa cell. Furthermore, the data showthat the two-cell model is applicable to other frog species. J. Exp. Zool.284:91-99, 1999. (C) 1999 Wiley-Liss, Inc.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 04/12/20 alle ore 01:03:32