Angiotensins stimulate in vitro ovulation and contraction of brook trout (Salvelinus fontinalis) follicles

Abstract

The effects of salmon angiotensin I (sAI) and human angiotensin II (hAII) on in vitro ovulation of preovulatory (preOV) brook trout (Salvelinus fontinalis) follicles were investigated. Both angiotensins increased levels of ovulation above that in controls after 12 hours of incubation. The increase was statistically significant in incubates with greater than 1 μM hAII. The effects of the angiotensins on follicle contraction were also studied indirectly by measuring the decrease in weight of punctured follicles taken prior to germinal vesicle breakdown. At 1 μM, both angiotensins significantly decreased the weight of punctured follicles after 16 hours of incubation. The angiotensin-stimulated decrease in weight was not blocked by indomethacin (10 μg/ml), indicating that follicle contraction was not prostaglandin-dependent. The data indicate that angiotensins might be directly involved in brook trout ovulation and the stimulatory effects of angiotensins on ovulation may be attributed to their effects on follicle contraction.

Identification of new participants in the rainbow trout (Oncorhynchus mykiss) oocyte maturation and ovulation processes using cDNA microarrays

“…In addition, several lines of evidence supported the idea of Ang II in blocking the inhibitory effect of theca cells on meiosis resumption of bovine oocytes [ 68 ]. In brook trout ( Salvelinus fontinalis ) salmon Ang I and human Ang II were both able to increase the level of in vitro spontaneous ovulation [ 69 ]. In the present transcriptomic study, we observed a dramatic increase of ace2 gene expression during the preovulatory period.…”

Effect of a low water concentration in chloride, sodium and potassium on oocyte maturation, oocyte hydration, ovulation and egg quality in rainbow trout

“…Somatic follicular layers appear to be stretched around the oocyte at that stage. Because of the angiotensinlike nature of the ovulatory process and the contractile actions of theca layers during ovulation (Hajnik and Goetz, 1998;Hsu et al, 1992), postovulatory follicles appear shrinked after ovulation. It was hypothesized that the modest (i.e., 20%), yet significant, increase in water content observed during rainbow trout FOM would contribute to the increasing pressure applied by the oocyte onto surrounding somatic layers and would ultimately mechanically facilitate the exit of the oocyte through a hole in somatic layers (Milla et al, 2006).…”