Steffl Martin, Schweiger Markus, Amselgruber W M Werner M
Department of Anatomy and Physiology, University of Hohenheim, Fruwirthstrasse 35, Stuttgart 70599, Germany.
Acta Histochem. 2004;106(2):137-44. doi: 10.1016/j.acthis.2003.10.006.
The inositol 1,4,5-trisphosphate receptor type 2 (IP(3)R-2) is an intracellular Ca(2+) release channel responsible for mobilizing of Ca(2+) from intracellular storage sites and plays a key role in biological processes such as fertilization, cell differentiation, and growth. To study the cell-type-specific IP(3)R-2 expression in porcine ovaries during different phases of the oestrous cycle, we used reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. A total of 24 ovaries from gilts were collected in early luteal, mid-luteal, and follicular phases of the oestrous cycle. When amplified with the primers common to IP(3)R-2, a RT-PCR product of the expected size (approximately 388 bp) was clearly detected in the follicular and early luteal phase of the oestrous cycle, but there was no detectable PCR product in the corpus luteum of the mid-luteal phase of the oestrous cycle. Immunohistochemical studies showed that IP(3)R-2 protein is expressed in granulosa cells and theca cells of growing follicles. IP(3)R-2 immunostaining was first detected during the late pre-antral stage in granulosa and theca cells. Granulosa cell IP(3)R-2 expression increased from the pre-antral to mid-antral stage, but was strongly reduced in pre-ovulatory follicles. In the developing corpus luteum, intense IP(3)R-2 immunostaining was also present in luteal cells, but undetectable in mid-luteal corpora lutea. Furthermore, oocytes, atretic follicles and regressed corpora lutea were negative for IP(3)R-2. Our results indicate that the expression of the IP(3)R-2 protein was downregulated in terminally differentiated granulosa cells of pre-ovulatory follicles when granulosa cells lose follicle-stimulating hormone responsiveness. Therefore, we strongly suggest that IP(3)R-2 may play an important role in the initiation and propagation of intracellular Ca(2+) signals during follicular development of the pig.
肌醇1,4,5 -三磷酸受体2型（IP(3)R-2）是一种细胞内钙离子释放通道，负责从细胞内储存位点动员钙离子，并在受精、细胞分化和生长等生物学过程中起关键作用。为了研究发情周期不同阶段猪卵巢中IP(3)R-2的细胞类型特异性表达，我们采用了逆转录-聚合酶链反应（RT-PCR）和免疫组织化学方法。从发情周期的黄体早期、黄体中期和卵泡期收集了共24个后备母猪的卵巢。用IP(3)R-2通用引物扩增时，在发情周期的卵泡期和黄体早期清晰检测到预期大小（约388 bp）的RT-PCR产物，但在发情周期黄体中期的黄体中未检测到PCR产物。免疫组织化学研究表明，IP(3)R-2蛋白在生长卵泡的颗粒细胞和卵泡膜细胞中表达。IP(3)R-2免疫染色最早在颗粒细胞和卵泡膜细胞的窦前晚期被检测到。颗粒细胞IP(3)R-2表达从窦前期到窦中期增加，但在排卵前卵泡中强烈降低。在发育中的黄体中，黄体细胞也存在强烈的IP(3)R-2免疫染色，但在黄体中期的黄体中未检测到。此外，卵母细胞、闭锁卵泡和退化黄体的IP(3)R-2呈阴性。我们的结果表明，当颗粒细胞失去促卵泡激素反应性时，IP(3)R-2蛋白的表达在排卵前卵泡的终末分化颗粒细胞中下调。因此，我们强烈建议IP(3)R-2可能在猪卵泡发育过程中细胞内钙离子信号的起始和传播中起重要作用。
