Physiological responses of European sea bass (Dicentrarchus labrax) exposed to increased carbon dioxide and reduced seawater salinities

BACKGROUND

The iono- and osmoregulatory capacities of marine teleosts, such as European sea bass (Dicentrarchus labrax) are expected to be challenged by high carbon dioxide exposure, and the adverse effects of elevated CO2 could be amplified when such fish migrate into less buffered hypo-osmotic estuarine environments. Therefore, the effects of increased CO2 on the physiological responses of European sea bass (Dicentrarchus labrax) acclimated to 32 ppt, 10 ppt and 2.5 ppt were investigated.

METHODS

Following acclimation to different salinities for two weeks, fish were exposed to present-day (400 µatm) and future (1000 µatm) atmospheric CO2 for 1, 3, 7 and 21 days. Blood pH, plasma ions (Na+, K+, Cl-), branchial mRNA expression of ion transporters such as Na+/K+-ATPase (NKA), Na+/K+/2Cl- co-transporters (NKCC) and ammonia transporters (e.g. Rhesus glycoproteins Rhbg, Rhcg1 and Rhcg2) were examined to understand the iono- and osmoregulatory consequences of elevated CO2.

RESULTS

A transient but significant increase in the blood pH of exposed fish acclimated at 10 ppt (day 1) and 2.5 ppt (day 21) was observed possibly due to an overshoot of the blood HCO3- accumulation while a significant reduction of blood pH was observed after 21 days at 2.5ppt. However, no change was seen at 32 ppt. Generally, Na + concentration of control fish was relatively higher at 10 ppt and lower at 2.5 ppt compared to 32 ppt control group at all sampling periods. Additionally, NKA was upregulated in gill of juvenile sea bass when acclimated to lower salinities compared to 32 ppt control group. CO2 exposure generally downregulated NKA mRNA expression at 32ppt (day 1), 10 ppt (days 3, 7 and 21) and 2.5ppt (days 1 and 7) and also a significant reduction of NKCC mRNA level of the exposed fish acclimated at 32 ppt (1-3 days) and 10 ppt (7-21 days) was observed. Furthermore, Rhesus glycoproteins were generally upregulated in the fish acclimated at lower salinities indicating a higher dependance on gill ammonia excretion. Increased CO2 led to a reduced expression of Rhbg and may therefore reduce ammonia excretion rate.

CONCLUSION

Juvenile sea bass were relatively successful in keeping acid base balance under an ocean acidification scenario. However, this came at a cost for ionoregulation with reduced NKA, NKCC and Rhbg expression rates as a consequence.

The Effect of Angiotensin on the Quality of In Vitro Produced (IVP) Sheep Embryos and Expression of Na(+)/K(+)/ATPase

BACKGROUND

The presence of rennin-angiotensin components in mammalian ovaries and their involvement in ovarian physiology have been established. In the present study, effects of angiotensin II (Ang II) on sodium-potassium adenosine triphosphatase (Na(+)/K(+)/ATPase) expression and development of sheep embryos was evaluated.

METHODS

The abattoir-derived Cumulus Oocyte Complexes (COC) were randomly allocated into three experimental groups; group I) in vitro Maturation (IVM) of oocytes in the presence of Ang II followed by in vitro fertilization (IVF)/in vitro Culture (IVC) (IVM group), group II) IVM/IVF of oocytes followed by IVC wherein the embryos were exposed to Ang II on day 4 of IVC (D4 group), and group III) IVM/IVF and IVC of oocytes without any angiotensin (Control). The blastocyst and hatching rates were recorded on days 6 to 8. Day 8 embryos were immunostained with primary and secondary antibodies against Na(+)/K(+)/ATPase α1 and β1 subunits.

RESULTS

Addition of Ang II during IVM and IVC significantly increased the hatching rate of blastocysts on day 8 compared to the control. The trophectoderm and total blastocyst cells' numbers were significantly increased by addition of Ang II to the IVM and IVC media, though the expression of Na(+)/K(+)/ATPase α1 and β1 subunits were positively influenced by the addition of Ang II on day 4 (D4 group).

CONCLUSION

In conclusion, it seems Ang II through positive effects on embryos, expressed as the greater hatching rate and blastocyst cell number, could increase the sheep embryo developmental rate. These improvements might be partly related to the greater expression of Na(+)/K(+)/ATPase α1 and β1 subunits when Ang II was added during IVC.

The Effect of Media Supplementation with Angiotensin on Developmental Competence of Ovine Embryos Derived from Vitrified-warmed Oocytes

BACKGROUND

This study was aimed to assess the effects of angiotensin II (Ang II) supplementation to the In Vitro Maturation (IVM) and In Vitro Culture (IVC) media of vitrified-warmed ovine oocytes on their developmental competence and expression of Na(+)/K(+)/ATPase in resulting embryos.

METHODS

The slaughterhouse-derived immature oocytes (n=1069) were randomly distributed into four experimental groups: groups I and II) IVM/IVF and IVC of fresh and vitrified oocytes without angiotensin supplementation (Control-Fresh and Control-Vit groups, respectively); group III) IVM of vitrified oocytes in the presence of Ang II followed by IVF/IVC (Vit-IVM group); and group IV) IVM/IVF of vitrified oocytes followed by IVC wherein the embryos were exposed to Ang II on day 4 of IVC (Vit-D4 group). The embryos were immunostained with primary antibodies against Na(+)/K(+)/ATPase α1 and β1 subunits.

RESULTS

In Vit-IVM and Vit-D4 groups, the rates of expanded and total blastocysts on day 7 as well as the proportion of blastocysts on day 8 were increased. The expression of Na(+)/K(+)/ATPase α1 and β1 subunits were positively influenced by the addition of Ang II on day 4 (Vit-D4 group).

CONCLUSION

The addition of Ang II to the IVM and IVC media could improve blastocysts formation in vitrified sheep oocytes. This improvement might be related to the greater expression of Na(+)/K(+)/ATPase α1 and β1 subunits when Ang II was added during IVC.