The effect of Sildenafil (viagra) on antral follicle development in sheep - Literature review Example

The endocrine, paracrine, and autocrine factors regulate the proliferation of granulosa cells, in which case the follicles then become gonadotrophin dependent, and their granulosa and theca cells will continue to proliferate and differentiate until ovulation. The formation of the fluid-filled antrum acts as the selective barrier, which enables the accumulation of substance within the follicular fluid and then envelops the oocyte and surrounding granulosa cells within some specialized microenvironment.

The changes in the vascular permeability mediate some processes in the follicle development, in which case it includes the antrum formation and oocyte maturation (Hunter 2003). Folliculogenesis, characterized by remarkable proliferation and differentiation of follicles somatic cells has the gonadotrophins controlling the dynamic process, in which case it also regulates the development of the ovarian follicle through the endocrine mechanism. In addition, other intraovarian mechanisms involves in the controlling of the folliculogenesis by modulating the response of follicles to circulating gonadotrophins.

Various researchers have had to classify the folliculogenesis into stages such as the recruitments stage, in which case it is the beginning of gonadotrophin-dependent folliculogenesis by the pool of healthy growing follicles. In sheep, the relations existing between the size at the recruitment stage (2mm) and size at which follicles becomes gonadotrophin dependent (2mm) is quite clear. Then there is the selection stage, and this is where there is a selection of follicles for further development.

There is the selection of the dominant follicle and suppression of remaining follicles and undergoes atresia. In sheep, there is the development of LH receptors on follicles where the diameter reaches four, 5 to 6, 8 and 25mm. At dominance process, there is rapid development and the maturation occurs. The size gap between the dominant follicle and the subordinate one in sheep may reach 2 to 3 mm (Temel Et al 2000). Sildenafil, or rather Viagra, contains nitric oxide, in which case it plays a pivotal role in platelet aggregation, disaggregation and neurotransmission (Dunzendorfer 2004).

Nitric oxide acts as the signaling agent in the NO/cGMP pathway due to the properties of Nitric Oxide. Therefore, the sildenafil or rather the Viagra use will result in some influence of antral follicle development in sheep. First, to begin with, the nitric oxide plays a role in the ovarian function. It plays the key role of controlling the ovarian vessels relaxation to accommodate the required changes in blood flow, blood volume and plasma exudation associated with follicle rapture during ovulation.

Therefore, using the Viagra will increase the relaxation of vessels, and hence there will be more blood flowing and volume including the plasma exudation (Dunzendorfer 2004). In addition, the nitric oxide influences the extent of damage after interruption in the supply of blood. Nitric oxide, which Viagra supplies, increases the blood flow to the hypoxic issues. Therefore, using the Viagra will raise the blood flow to the hypoxic tissue, hence, triggering the increased blood perfusion to match the delivery of oxygen with need.

Moreover, the use of Viagra will improve the regulation of angiogenesis, apoptosis and luteolysis. Furthermore, the uses of Viagra will incre