The Influence of Lactate and Dipyridamole on Myocardial Fatty Acid Metabolism in Man, Traced with ¹²³l-17-lodo-heptadecanoic Acid^[*]

Changes in myocardial metabolism can be detected externally by registration of time-activity curves after administration of radioiodinated fatty acids. In this scintigraphic study the influence of lactate on fatty acid metabolism was investigated in the normal human myocardium, traced with ¹²³l-17-iodoheptadecanoic acid (¹²³l-17-HDA). In patients (paired, n = 7) lactate loading decreased the uptake of ¹²³l-17-HDA significantly from 27 (control: 22-36) to 20 counts/min/pixel (16-31; p <0.05 Wilcoxon). The half-time value increased to more than 60 rriin (n = 5), oxidation decreased from 61 to 42%. Coronary vasodilatation, a well-known side effect of lactate loading, was studied separately in a dipyridamole study (paired, n = 6). Coronary vasodilatation did not influence the parameters of the time-activity curve. These results suggest that changes in plasma lactate level as occurring, among other effects, during exercise will influence the parameters of dynamic ¹²³l-17-HDA scintigraphy of the heart.

Zusammenfassung

Nach intravenöser Applikation von jodmarkierter Fettsäure können Veränderungen im Myokardstoffwechsel durch externe Registrierung von Zeitaktivitätskurven festgestellt werden. In dieser szintigraphischen Studie wurde mittels ¹²³I-17-Jod-Heptadekansäure (¹²³J-17-HDA) der Einfluß des Laktats auf den Fettsäurestoffwechsel im gesunden menschlichen Myokard untersucht. Bei Patienten (n = 7) verringerte gleichzeitige Gabe von Laktat die myokardiale Aufnahme von ¹²³I-17-HDA signifikant von 27 (Streubreite 22-36) auf 20 Counts/ min/Pixel (16-31; p <0,05). Die Halbwertszeit stieg auf Werte über 60 min (n = 5), die relative Poolgröße der Oxidation verringerte sich von 61 auf 42%. Die koronare Gefäßerweiterung, eine bekannte Nebenwirkung der Laktat-Belastung, wurde in einer Dipyridamolstudie separat untersucht (n = 6). Die koronare Dilatation hatte keinen Einfluß auf die Parameter. Diese Ergebnisse legen nahe, daß bei Änderungen im Plasma-Laktatspiegel die myokardialen Parameter der dynamischen ¹²³I-17-HDA-Szintigraphie beeinflußt werden.

* Presented at the 34th Meeting of the Society of Nuclear Medicine, Toronto, 1987 (J Nucl Med 1987; 28: 567).

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