Relationship between follicular fluid steroids and tissue renin concentrations and secretion rates in bovine ovaries

Summary

The relationship between follicular fluid concentrations of oestradiol (E₂) and progesterone (P₄), and follicular wall tissue renin concentrations and in-vitro secretion rates was investigated. The follicular fluid concentrations of prorenin correlated negatively with oestradiol and the E₂/P₄ ratio, and positively with progesterone in accordance with earlier findings. The high concentrations of active renin and prorenin in the follicular wall tissue, and the secretion rates of both active renin and prorenin all correlated positively with oestradiol and the E₂/P₄ ratio, but negatively with progesterone. These findings suggest that atretic follicles have higher follicular fluid renin concentrations but lower tissue renin concentrations and in-vitro secretion rates than healthy non-atretic follicles. The high follicular fluid prorenin concentrations in atretic follicles are most likely caused by a high prorenin secretion rate earlier in the oestrus cycle. The existence of relationships between the follicular fluid steroids and the follicular wall concentrations and secretion rates of active renin and prorenin indicates an interaction between the reninangiotensin system and steroidogenesis, but it may also reflect regulation by common factors, such as gonadotropins.

Key words

Cattle - oestradiol - ovary - progesterone - renin