Human forearm and kidney conversion of arachidonic acid to prostaglandins

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Abstract
The capacity of the human forearm and kidney to synthetize different prostaglandins (PGs) was studied, together with the quantitative relationship between the various PGs formed in these organs. 14C-labelled arachidonic acid (14C-AA) was infused in healthy male volunteers at a constant rate into the brachial or the renal artery, with simultaneous sampling of regional venous blood. The venous plasma content of 14C-PGs was extracted, separated with thin-layer chromatography (TLC) and quantified using fractionated liquid scintillation spectrometry. Most of the 14C-AA infused was metabolized and radiopeaks parallel to unlabelled standards of PGD2, PGE2, PGFja, 6-keto-PGF, and 13,14-dihydro-15-keto-PGEj (Me) were obtained. The chromatograms of both the forearm and the kidney plasma contained all the peaks described, but the relative distribution of the I4C-PGs differed between the two tissues. In the cubital venous plasma, the main PG (apart from Me) was 6-keto-PGFla, indicating a considerable synthesis of PGI2 in the forearm. In the renal venous plasma, on the other hand, PGD2 accounted for the largest part of the authentic 14C-PGs found. Besides the tissue differences, large inter-individual variations were observed. The results demonstrate the existence of both a considerable tissue specificity and an appreciable inter-individual variation in the local conversion of AA to PGs in man.