Effects of age on vascular prostaglandin production in male and female rats

The incidence of vascular disorders increases with age, and is also higher in men than in women. Since prostaglandin (PG)I2 produced by blood vessels has been proposed to have a protective function in the cardiovascular system, reduced vascular PGI2 production with age and lower vascular PGI2 production in males than in females may be causes for these increases in the incidence of vascular disorders. The production of prostaglandins by blood vessels has therefore been investigated in young (2 to 3 months) and old (12 to 14 months), male and female rats. The amounts of 6-keto-PGF1 alpha (reflecting PGI2 formation) synthesized by endothelial cell suspensions were significantly lower in old compared to young male rats, but did not differ between old and young female rats. The amounts of 6-keto-PGF1 alpha synthesized by homogenates of aortic smooth muscle were considerably higher in old compared to young, male and female rats. However, the basal output of 6-keto-PGF1 alpha from the perfused aorta in vitro did not change significantly with increase in age and, if anything, tended to be higher in the older rats, of both sexes. Furthermore, the basal output of 6-keto-PGF1 alpha from the aorta was significantly higher in young and old, male rats compared to young and old, female rats, respectively. Similar findings were observed regarding basal 6-keto-PGF1 alpha output from the perfused mesenteric arterial bed in vitro. The increases in output of 6-keto-PGF1 alpha from the mesenteric arterial bed in response to noradrenaline and angiotensin II were not diminished with age in either male or female rats. Consequently, PGI2 output from the blood vessels studied did not decrease with age, nor was it lower in male rats compared to female rats. The blood pressure was significantly higher in the old rats compared to the young rats. Also, the vascular output of PGF2 alpha, a vasoconstrictor, was higher in the old rats. The increase in blood pressure with age may therefore be connected with this increase in vascular PGF2 alpha production in both sexes.