Expression of aquaporin 4 in the chicken ovary in relation to follicle development

Abstract

In the mammalian ovary, aquaporins (AQPs) are thought to be involved in the regulation of fluid transport within the follicular wall and antrum formation. Data concerning the AQPs in the avian ovary is very limited. Therefore, the present study was designed to examine whether the AQP4 is present in the chicken ovary, and if so, what is its distribution in the ovarian compartment of the laying hen. Localization of AQP4 in the ovarian follicles at different stage of development was also investigated. After decapitation of hens the stroma with primordial follicles and white (1-4 mm), yellowish (4-8 mm), small yellow and the three largest yellow pre-ovulatory follicles F3-F1 (F3 < F2 < F1; 20-36 mm) were isolated from the ovary. The granulosa and theca layers were separated from the pre-ovulatory follicles. The AQP4 mRNA and protein were detected in all examined ovarian compartments by the real-time PCR and Western blot analyses, respectively. The relative expression of AQP4 was depended on follicular size and the layer of follicular wall. It was the lowest in the granulosa layer of pre-ovulatory follicles and the highest in the ovarian stroma as well as white and yellowish follicles. Along with approaching of the largest follicle to ovulation the gradual decrease in AQP4 protein level in the granulosa layer was observed. Immunoreactivity for AQP4 was present in the granulosa and theca cells (theca interna ≥ theca externa > granulosa). The obtained results suggest that AQP4 may take part in the regulation of water transport required for follicle development in the chicken ovary.

Expression of aquaporin 4 in the chicken oviduct following tamoxifen treatment

“…This finding implies a possible involvement of AQP4 in the regulation of oviductal fluid volume and composition, and cell volume in the hen oviduct during different physiological states, similarly as it was strongly suggested for AQPs in the mammalian oviduct, uterus or vagina (Huang et al, ; Zhu et al, ). Our results, obtained for the first time in birds, are largely consistent with those previously reported in the human and rodent uterus or vagina, and extend the number of avian reproductive tissues in which the presence of AQP4 has recently been shown, that is the ovarian stroma and follicles at different stages of development (Nowak et al, ).…”

“…Total RNA was extracted from collected tissues with the TRI Reagent and were reverse‐transcribed (2 μg) with a High‐Capacity cDNA Reverse Transcription Kit (Applied Biosystems, Foster City, CA, USA) following the manufacturer's protocol. The duplex real‐time qPCR was carried out as described recently (Nowak et al, ) in a 10 μl volume containing 5 μl of TaqMan Gene Expression Master Mix, 0.5 μl TaqMan Gene Expression Assays with a specific TaqMan MGB‐probe and one pair of primers ( AQP4 , assay ID: Gg03346640_m1, GenBank accession no. NM_001004765.1, amplicon size: 87 bp; Applied Biosystems), 0.5 μl of Eucaryotic 18S rRNA Endogenous Control (pair of primers and TaqMan probe‐labelled VIC/TAMRA, cat # 4310893E, amplicon size: 187 bp; Applied Biosystems), 3 μl of water and 1 μl of cDNA (10x diluted samples after the RT).…”

“…Furthermore, Yang, Lim, Bae, and Song (2016) demonstrated an increase in the expression of AQP3 in the chicken model of ovarian tumours and revealed that AQP3 is involved in the development of the chicken oviduct, which is regulated by oestrogen. Our recent study showed the distribution of AQP4 in the ovary of the laying hen, suggesting that this AQP may take part in the regulation of follicle growth by transportation of water (Nowak et al, 2017).…”

“…Total RNA was extracted from collected tissues with the TRI Reagent and were reverse-transcribed (2 μg) with a High-Capacity cDNA Reverse Transcription Kit (Applied Biosystems, Foster City, CA, USA) following the manufacturer's protocol. The duplex realtime qPCR was carried out as described recently (Nowak et al, 2017) in a 10 μl volume containing 5 μl of TaqMan Gene Expression Master Mix, 0.5 μl TaqMan Gene Expression Assays with a specific TaqMan…”

“…Furthermore, Yang, Lim, Bae, and Song () demonstrated an increase in the expression of AQP3 in the chicken model of ovarian tumours and revealed that AQP3 is involved in the development of the chicken oviduct, which is regulated by oestrogen. Our recent study showed the distribution of AQP4 in the ovary of the laying hen, suggesting that this AQP may take part in the regulation of follicle growth by transportation of water (Nowak et al, ). This study was designed to examine whether AQP4 is present in the chicken oviduct, and if so, whether its expression changes during pause in laying induced by tamoxifen (TMX; oestrogen receptor modulator) treatment.…”