• Animal cells and systems
• /
• 제3권4호
• /
• pp.385-391
• /
• 1999

Changes in the levels of prostaglandian F$_{2a}$ (PGF$_{2a}$) and E$_2$ (PGE$_2$) in culture medium during in vitro ovulation of Rana dybowskii follicles were examined. The ovulation was induced by frog pituitary homogenate (FPH) or TPA (12-O-tetradecanoylphorbol-13-acetate, a protein kinase activator) and the levels of PGs were measured by radioimmunoassay. When the ovarian follicles were cultured, only a few oocytes were ovulated by 12 h, but half of them were ovulated by 24 h in response to FPH, whereas around 30% of oocytes were ovulated by 12 h and maximum ovulation (around 50%) occurred by 24 h in response to TPA. Without any stimulation (control), no ovulation occurred. TPA elevated the level of PGF$_{2a}$ to high levels when compared to control (basal levels), but the increase by FPH was less evident. Likewise, the levels of PGE$_2$ increased markedly in response to TPA, but rather decreased by FPH treatment. Interestingly, PGF$_{2a}$ induced ovulation but PGE$_2$ suppressed FPH- or PGF$_{2a}$-induced oocyte ovulation. Basal levels of PGs Increased steadily during culture. When theca/epithelium (THEP) layer and granulosa cell-enclosed oocytes (GCEOs) were separated by microdissection and cultured independently, higher levels of both PGs were secreted by THEP than by GCEOS. Synthesis of PGs by follicle or follicular components was strongly suppressed by exogenous cAMP or indomethacin. These results suggest that: 1) PGF$_{2a}$ plays an important role in Rana ovulation, 2) protein kinase C is involved in PGs production, and 3) thecal epithelium layer is responsible for the PGs production in Rana.

• 한국동물학회지
• /
• 제33권2호
• /
• pp.175-182
• /
• 1990

참구개구와 옴개구리의 여포를 생체외 배양하면서 progesterone (P$_4$)생성과 난자의 성숙 및 cyclic(cAMP)의 조절작용을 조사하였다.참개구리의 여포에 뇌하수체 추출물(frog pituitary homogenate.FPH)을 처리하면 농도에 의존하여 여포의 P$_4$생성이 증가하였으며 난자의 성숙(핵붕괴)이 일어났다. 이들 여포들을 배양하면서 3시간 간격으로 호르몬이 여포에 축적된 양, 배양액에 분비된 양 및 난자의 성숙율을 조사한 결과 FPH처리군에서 P$_4$는 3-6시간에 최고치 (여포내,약 400pg/여포;분비량,약 800pg/여포)를 나타내었으며 난자의 핵붕괴는 9-12시간에 일어났다. 상기 여포들과 같은 조건으로 배양하면서 forskolin과 3-isobutyl-1-methylxanthine(IBMX)을 배양액에 처리하여 간접적으로 여포내 cAMP의 농도를 높여주면 FPH와 유사한 양사으로 호르몬의 생성을 촉진하였다. 그러나 난자의 성숙은 전혀 일어나지 않았다. 옴개구리의 여포를 배양하면서 FPH를 처리하였을 때는 아무 처리를 하지않은 대조군과 비교하여 거의 P$_4$의 생성을 촉진하지 않았으며 난자의 성숙도 유도하지 못했다, 그러나 이들에게 forskolin과 IBMX를 처리하면 P$_4$의 생성을 현저하게 촉진하여 다량의 P$_4$가 여포와 (약 800pg/여포) 배양액에 (1700pg/여포)축적되었다.

• 한국동물학회지
• /
• 제39권3호
• /
• pp.266-272
• /
• 1996

봄에 채집한 참개구리의 난소조각 배양계를 사용하여 난자의 배란과정에 프로스타글란딘과 protein kinase C(PKC)가 관여하는 지를 조사하였다. 난소조각을 배양하면서 뇌하수체추출물(FPH) 혹은PKC의 활성제인 12-O-tetradecanoyl phorbol-13-acetate (TPA)를 처리한 후 배란율과 프로스타글란딘의 생상량을 방사면역측정법으로 조사한 결과 농도에 의존하여 난자의 배란이 유도 되었으며 프로스타글란딘의 생성이 촉진되었다. FPH와 TPA에 의한 배란과 프로스타글란딘 생성은, 4월 보다는 5월에 채집한 개구리에서 훨씬 더 효과적이었다. FPH처리는 프로스타글란딘과 함께 progestreone의 생성을 촉진하였으나 TPA는 progestreone의 생성을 촉진하지는 못하였다. FPH와 TPA에 의한 배란과ㅣ 프로스타글라딘 생성 억제제인 indomethacin에 의해서는 난자의 배랑니 억제되지는 않았다. 이러한 결과들은 참개구리 난자의 배란 과정에 PKC의 활성화가 중요한 역할을 하며, 프로스타글라딘의 생성이 매개할 것으로 생각된다.

• 한국동물학회:학술대회논문집
• /
• 한국동물학회 1994년도 한국생물과학협회 학술발표대회
• /
• pp.156.2-156
• /
• 1994

• 한국동물학회지
• /
• 제39권3호
• /
• pp.257-265
• /
• 1996

참개구리를 사용하여 난소내 여포들이 성장시기에 획즉하게 되는 스테로이드들의 생성능력을 조사하였다. 개구리로부터 중간(0.7-1.11mm) 크기 이하의 여포들을 분리한 다음 전구스테로이들이나 뇌하수체추출물(FPH)을 포함한 배양액에서 6시간 배양 후 이들에 의해 산물스테로이드로 전환된 양을 방사면역 측정법으로 조사하였다. FPH의 처리는 중간 크기의 여포만 스테로이드들의 생성을 현저히 촉진하고 작은 여포들(0.35-0.7mm)에서는 촉진효과가 매우 미약하였다. Progenenolone의 첨가는 가장 작은 여포 (0.22-0.4mm)들에 의해서도 progesterone(P$_4$)으로 전환되었다. 그러나 가장 작은 여포에서는 P$_4$를 첨가했을 때에도 역시 같은 현상이 나타났다. 작은 여포와 중간 여포들에 의한 전환된 스테로이드들의 양을 단위표면적의 전환량으로 계산 비교해 본 결과 전환된 양은 거의 같았다. 이는 작은 여포의 여포세포들 (granulosa cells)이 이미 E$_2$에 이르는 모든 중간 산물들을 생성할 능력을 가졌다는 것을 의미한다. 그러나 이들이 FPH에 의해서는 스테로이드를 조금밖에 생성하지 못하는 것으로 보아 아직 부족한 또다른 요인들이 있는것으로 추정된다.

• Animal cells and systems
• /
• 제11권1호
• /
• pp.1-8
• /
• 2007

Recently, we have shown that some endocrine disruptors, heavy metals, organotins and azoles suppressed steroidogenic enzymes such as P450 side-chain cleavage enzyme (P450scc) and aromatase in bullfrog ovarian follicles. In the present study, by using an amphibian ovarian follicle culture system, we examined the effects of these endocrine disruptors on maturation and ovulation of oocytes from Rana dybowskii in vitro. Ovarian fragments or isolated follicles were cultured for 24 h in a medium containing frog pituitary homogenate (FPH) or progesterone ($P_{4}$) with or without endocrine disruptors, and oocyte maturation (germinal vesicle breakdown, GVBD) and ovulation were examined. Among the organotins, tributyltin (TBT) strongly inhibited both FPH-and $P_{4}-induced$ oocyte maturation ($ED_{50}$:0.6 and 0.7 ${\mu}M$, respectively); however, tetrabutyltin (TTBT) and dibutyltin (DBT) showed only partial suppression, while monobutyltin (MBT) showed no inhibitory effect. All of the organotins suppressed $P_{4}-induced$ oocyte ovulation very effectively at a low concentration, and TBT and DBT exerted an inhibitory effect on FPH-induced ovulation. Among the heavy metals, mercury (Hg), cadmium (Cd) and cobalt (Co) were very effective in inhibiting FPH-induced oocyte maturation and ovulation, while lead (Pb), arsenite (As) and zinc (Zn) were less effective. However, all of the heavy metals suppressed FPH-induced oocyte ovulation at a high dose ($100{\mu}M$). Among the azoles, itraconazole (ICZ), ketoconazole (KCZ) and clotrimazole (CTZ) effectively inhibited FPH-induced oocyte maturation and ovulation, while econazole (ECZ), miconazole (MCZ) and fluconazole (FCZ) were considerably less effective. These results demonstrated that the abovementioned endocrine disruptors exhibited differential effects on oocyte maturation and ovulation in amphibian follicles and that the frog ovarian culture system could be used as an effective experimental tool to screen and evaluate the toxicity of various endocrine disruptors in vitro.

• 한국발생생물학회지:발생과생식
• /
• 제13권3호
• /
• pp.163-172
• /
• 2009

Some organotin compounds such as butyltins and phenyltins are known to induce impo-sex in various marine animals and are considered to be endocrine disruptors. In this study, the effect of organotins on follicular steroidogenesis in amphibians was examined using ovarian follicles of Rana dybowskii and Rana catesbeiana. Isolated follicles were cultured for 6 or 18 h in the presence and absence of frog pituitary homogenate (FPH) or various steroid precursors, and the levels of product steroids in the culture media oassay. Among the butyltin compounds, tributyltin (TBT) strongly and dose-dependently inhibited the FPH-induced synthesis of pregnenolone ($P_5$) and progesterone ($P_4$) by the follicles. TBT also strongly suppressed the conversion of cholesterol to $P_5$ and partially suppressed the conversion of $P_5$ to $P_4$. A high concentration of dibutyltin (DBT) also inhibited steroidogenesis by the follicles while monobutyltin and tetrabutyltin had negligible effects. The toxic effect of TBT or DBT was irreversible and a short time of exposure (30 min) was enough to suppress steroidogenesis. All the phenyltin compounds significantly inhibited FPH-induced $P_5$ synthesis by the follicles. The effective dose of 50% inhibition by diphenyltin was $0.04\;{\mu}M$ and those of monophenyltin and triphenyltin were $0.24\;{\mu}M$ and $0.3\;{\mu}M$, respectively. However, none of the phenyltin compounds significantly suppressed the conversion of $P_4$ to $17{\alpha}$-hydroxyprogesterone ($17{\alpha}$-OHP) (by $17{\alpha}$-hydroxylase), $17{\alpha}$-OHP to androstenedione (AD) (by $C_{17-20}$ lyase), or AD to testosterone by the follicles. Taken together, the data show that among the steroidogenic enzymes, P450scc in the follicles is the most sensitive to organotin compounds and that an amphibian follicle culture system can be a useful screening model for endocrine disruptors.

• 한국동물학회지
• /
• 제31권3호
• /
• pp.177-184
• /
• 1988

북방산개구리의 여포를 인공배양하면서 여포의 progesterone(p$_4$) 의 생성양상과 cAMP의 조절작용을 조사하여 보았다. 배양중인 여포에 뇌하수체 추출물(frog pituitary homogenate,FPH)을 처리하였을 때 배양 한시간 부터 여포내 p$_4$의 양이 급격히 증가하였다. 그러나 생성된 p$_4$의 최대양이나(약 60-300pg/follicle),peak를 이루는 시간이(2시간 이후)개체에 따라 차이가 있었다. FPH의 처리를 받지않은 대조군에서는 배양기간에 관계없이 여포내에서 대략 10pg/follicle정도의 p$_4$가 측정되었으나 예외인 개체도 있었다. 배양액내로 분비된 p$_4$의 양은 여포내에 생성된p$_4$양의 약 60%정도 이었다. 배양액에 adenlate cyclass의 촉진제인 forskolin이나phosphodiesterase의 저해제인 3-isoburyl-1- methylxanthine(IBMX)을 동시에 혹은 따로 처리하면 p$_4$의 생성과 분비가 역시 증가하며 모든 양상이 FPH의 자극에 의한 것과 거의 같았다. 따라서 개구리여포의 스테로이드생성은 cAMP를 통하여 조절된다는 것과 여포세포내에는 cAMP의 생성과 분해에 관계하는 효소들이 있다는 것을 알았다.

• Animal cells and systems
• /
• 제10권4호
• /
• pp.211-217
• /
• 2006

Heavy metals are well known as important environmental pollutants and also considered as endocrine disrupters. This study was performed to evaluate the direct effects of heavy metals such as cadmium (Cd), zinc (Zn), mercury (Hg), lead (Pb), cobalt (Co), and arsenic (As) on the various steroidogenic enzymes in frog ovarian follicles. Ovarian follicles from Rana catesbeiana were isolated and cultured for 18 hours in the presence of frog pituitary homogenate (FPH, 0.05 gland/ml) or various steroid precursors with or without heavy metals (0.01-100 ${\mu}M$), and steroid levels in the follicle or culture medium were measured by radioimmunoassay (RIA). Thus, the steroidogenic enzyme activities were indirectly evaluated by measuring the converted steroid levels from the added precursor steroid. Among heavy metals, Hg, Cd and Zn significantly inhibited FPH-induced pregnenolone ($P_5$) production by the follicles ($EC_{50},\;4.0{\mu}M,\;25.6{\mu}M\;and\;5.7{\mu}M$, respectively ), and also suppressed the conversion of testosterone (T) to estradiol $17{beta}\;(E_2)\;(EC_{50},\;4.2{\mu}M,\;7.5{\mu}M\;and\;80.0{\mu}M) while Pb, Co and As are not or less effective in the inhibition. Other enzymes such as $C_{17-20}$ lyase and $17{\beta}$-hydroxysteroid dehydrogenase ($17{\beta}$-HSD) were suppressed only in the high concentration of Hg, Cd and Zn. Taken together, these data demonstrate that cytochrome P450 side chain cleavage (P450scc) and aromatase are much more sensitive to heavy metals than other steroidogenic enzymes and Hg, Cd and Zn show stronger toxicity to follicles than other heavy metals examined.

• Animal cells and systems
• /
• 제5권1호
• /
• pp.45-50
• /
• 2001

Rana ovarian follicles consist of oocyte, vitelline envelope, granulosa cells, and theca/epithelial layer. Using scanning electron microscopy, the surface structure of each follicular component was investigated. Changes in oocyte surface during oocyte maturation were also examined. Theca/epithelial layer was almost transparent and some blood vessels and granulosa cells were observed underneath in intact follicle. The number of granulosa cells was estimated to be 6700-7200 per oocyte. The granulosa cells partially overlapped each other and their microvilli penetrated the vitelline membrane via holes present in the vitelline envelope and seemed to be linked to oocyte microvilli. After removal of the vitelline envelope by microforcep, oocyte microvilli were observed on the surface of the devitellined oocyte. The oocyte microvilli formed partial clusters on the surface of white spot area which appears iust before germinal vesicle breakdown (GVBD), whereas they were evenly distributed in other areas. The microvilli became shorter and less dense with oocyte maturation. The lengths of oocyte microvilli in the immature and mature oocyte were 1.5 $\mu$m and 0.6 $\mu$m, respectively. The present study suggests a fundamental structural change occurring on the oocyte surface during maturation.