16alpha-hydroxy-progesterone as a sex hormone antagonist: effect on venous diameters in the female mouse

16α-hydroxyprogesterone: origin, biosynthesis and receptor interaction

The metabolism of progesterone (PROG) by cytochrome P450 17α-hydroxylase/17,20-lyase (CYP17A1) results in the formation of both 17α-hydroxyprogesterone (17-OHPROG) and 16α-hydroxyprogesterone (16-OHPROG) in humans. Unlike 17-OHPROG, 16-OHPROG is not metabolised further in steroidogenic tissue. While this metabolite can be readily detected in serum and urine, its physiological role remains unclear. This paper reviews the production of 16-OHPROG by human CYP17A1 by providing insight into the catalysis of PROG by CYP17A1 and highlights the role of Ala105 in the 16α-hydroxylation reaction. As 16-OHPROG has been putatively linked to reproductive function, we investigated the interaction of this steroid metabolite with both isoforms of the human progesterone receptor (hPR). We show for the first time that 16-OHPROG can bind to both hPR-A and hPR-B and act as an agonist for both receptors.

Specific response of ovarian and uterine veins of mice to sex hormones

Pellets of glass (control), progesterone (P), testosterone (T), and estradiol-17beta (E) were placed on the mesentery or subcutaneously in the flank in ovariectomized (O) and ovariectomized-hysterectomized (OH) mice, insuring that all or most of the hormone would pass through the superior mesinteric or circumflex iliac veins. After 21 days the diameters of these and of the ovarian, uterine, and femoral veins and inferior vena cava were measured at autopsy. T and E caused significant enlargement of the uteri; E was also responsible for bladder distention. The ovarian and uterine veins enlarged significantly in mice treated with T and E as compared to the controls. All other veins failed to respond to P, T, and E. The evidence demonstrates a specific response of ovarian and uterine veins in O and OH mice to T and E.