A RENIN-LIKE ENZYME IN RAT LUTEAL TISSUE - EVIDENCE OF LOCAL SYNTHESIS AND ITS REGULATION DURING PREGNANCY

Changes in the concentration of a renin-like enzyme were studied in androgenized rats in which a single luteal phase was induced by the administration of chorionic gonadotrophin. A significant increase in the luteal renin-like enzyme (RLE) concentration was found between the youngest corpora lutea (48 h old) and the oldest one studied (6 days old). The luteal RLE content varied independently of changes in plasma renin concentration. These results suggest that this enzyme was produced locally. The lack of correlation between the luteal RLE and plasma prolactin supports our previous observation that the changes in luteal renin concentration appear not to be prolactin-dependent. Furthermore, the suckling-associated hormones appear not to be related with the regulation of luteal RLE concentration, since the values were not modified in androgenized maternal rats which were suckling when compared with the controls. Changes in luteal renin concentration were also studied during pregnancy. A significant increase was found a few hours after a fertile mating which reached a peak on day 1 of pregnancy, followed by a rapid decrease to low levels throughout the remainder of the pregnancy. Because the renin-angiotensin facilities angiogenesis, luteal renin may act as an angiogenic factor, stimulating blood vessel growth in the corpora lutea. An alternative hypothesis is that the increase in RLE could be a trigger for calcium flux redistribution and steroid biosynthesis.