Studies on the prostaglandin synthesizing capacity of several blood vessels from male and female rats

Prostaglandin (PG) I2 (measured as 6-keto-PGF1 alpha) was the major PG synthesized by homogenates of the aorta from male rats, followed by lesser quantities of PGF2 alpha and PGE2. The amounts of 6-keto-PGF1 alpha synthesized by homogenates of the vena cava, mesenteric artery and femoral artery were much less than synthesized by the aorta, and were similar to the amounts of PGF2 alpha and PGE2 synthesized. The amounts of 6-keto-PGF1 alpha synthesized by homogenates of the aorta were 30% lower in female rats than in male rats. The amounts of 6-keto-PGF1 alpha and PGF2 alpha synthesized by homogenates of the aorta from female rats were similar, but the amounts of PGE2 synthesized were lower. The amounts of 6-keto-PGF1 alpha synthesized by homogenates of the aorta and femoral artery of female rats were similar, but the amounts of 6-keto-PGF1 alpha synthesized by homogenates of the mesenteric artery and vena cava were lower and were similar to the amounts of PGF2 alpha and PGE2 synthesized. The amounts of 6-keto-PGF1 alpha synthesized by the vena cava were significantly lower (P less than 0.05) and the amounts of 6-keto-PGF1 alpha and PGF2 alpha synthesized by the femoral artery and aorta, respectively, were significantly higher (P less than 0.05) in female rats than in male rats. The total amount of 6-keto-PGF1 alpha, PGF2 alpha and PGE2 synthesized by the aortae of male and female rats did not differ, indicating that the higher output of 6-keto-PGF1 alpha from the aorta of male rats compared to female rats is not due to a higher concentration of PGH2 synthetase in the aortic tissue of male rats. However, the shift in the relative amounts of 6-keto-PGF1 alpha and PGF2 alpha synthesized by the aorta of female rats in favour of PGF2 alpha may be responsible for the lower output of 6-keto-PGF1 alpha from the aorta of female rats. Oestradiol and progesterone had no effect on the amounts of 6-keto-PGF1 alpha, PGF2 alpha and PGE2 synthesized by homogenates of the aorta and vena cava from intact and ovariectomized, female rats. However, ovariectomy increased the amounts of 6-keto-PGF1 alpha and PGE2 synthesized by the aorta and vena cava, respectively, an effect not reversed by oestradiol and progesterone treatment.