Effects of animal maturity on smooth muscle and blood pressure responses to prostaglandins E2 and F2α

Abstract

The effects of prostaglandins E2 (PGE2) and F2α (PGF2α) on muscle strips from mature and immature rats and guinea-pigs and on rat blood pressure were investigated in the presence of atropine. The colon and stomach strips from immature rats were equally responsive to PGE2 and PGF2α whereas mature colons were significantly more sensitive to PGF2α and mature stomach strips significantly more sensitive to PGE2. On the ileum from immature guinea-pigs the maximum responses to PGE2 and PGF2α were 16 and 8% of the histamine maximum respectively. The corresponding figures on the mature ileum were 86 and 75%. Whereas PGE2 was only twice as active as PGF2α on immature ilea, it was ten times more active than PGF2α on mature muscles. On blood pressure PGF2α and PGE2 were both hypotensive in immature rats whereas PGE2 was hypotensive and PGF2α hypertensive in mature rats. The results suggest that as the animal gets older, receptors for prostaglandins became increasingly differentiated.