Abstract: | PGI2 and 6-keto-PGF1α were converted to 6-methoxime-PGF1α (6-MeON-PGF1α) by treatment with methoxyamine HCl in acetate buffer. The formed 6-MeON-PGF1α was measured by radioimmunoassay. Antisera were raised in rabbits after immunization against 6-MeON-PGF1α-BSA conjugate. Diluted 1:20.000 to bind 50% of the tracer (3H-6-MeON-PGF1α, 100 Ci/mmol), the antiserum cross reacted 0.8% with PGE2, 1% with PGF2α and less than 0.2% with PGD2, PGF1α, PGF2β and TXB2. The radioimmunoassay was used to estimate release of PGI2 and 6-keto-PGF1α from chopped rabbit renal medulla and cortex incubated in Krebs-Ringer bicarbonate buffer (37°C, 30 min). The 6-keto-PGf1α radioimmunoassay was validated in biological samples by mass fragmentography. The chopped medulla (n=5) released 38±9 ng/g/min and the cortex (n=5) 4.7±2.0 ng/g/min, while the release of immunoreactive PGE2 (iPGE2) and iPGF2α was 171±26 and 74±13 ng/g/min from the medulla and 4.3±1.3 and 2.7±0.3 ng/g/min from the cortex, respectively. The results confirm previous findings, which indicate that in the renal medulla prostaglandin endoperoxides are mainly transformed to prostaglandins, while in the cortex transformation to PGI2 seems to be of greater importance. |