Myocardial Uptake of Iodinated Free Fatty Acids and ²⁰¹T1 in Experimental Ischemia

Summary

In an experimental study, we evaluated the uptake of (¹³¹I)-17-iodo heptadecanoic acid (¹³¹I-HDA), (¹²⁵I)-15-4 (4-iodophenyl) pentadecanoic acid (¹²⁵I-PPA) and thallium-201 (²⁰¹T1) in the dog heart. Twenty dogs were studied and divided into 3 groups: in group A, 10 dogs (4 normal, 6 with coronary artery occlusion) were studied with ¹³¹I-HDA and ²⁰¹T1; in group B, 5 dogs (with occlusion) received ¹²⁵I-PPA and ²⁰¹T1; and in group C, 5 dogs (with occlusion) were studied with ¹²⁵I-PPA and ¹³¹I-HDA. Two min after administration of the compounds the hearts were excised and stored in formaldehyde. After sectioning of the left ventricle, total uptake was counted and expressed in percentage of injected dose. Uptake in the normal myocardium (group A) was 4.2 ±0.6% for ¹³¹I-HDA and 4.6 ±0.7% for ²⁰¹T1; in the occluded dog hearts (group A) we measured values of 2.6 ±0.4% for ¹³¹I-HDA (p<0.001) and 3.4 ±0.6% for ²⁰¹T1 (p<0.01). Uptake of ¹³¹I-HDA, ¹²⁵IPPA and ²⁰¹T1 in groups B and C was not significantly different: group B, ¹²⁵I-PPA 2.8 ±0.8% and ²⁰¹T1 ± 0.5%; group C, ¹²⁵I-PPA 1.9 ±0.7% and ¹³¹I-HDA 1.6 ±0.6%. Moreover, regional distribution of both iodinated fatty acids was quite comparable with the distribution of ²⁰¹T1. We conclude that ¹³¹I-HDA and ¹²⁵I-PPA show similar uptake as ²⁰¹T1 and are distributed according to coronary artery perfusion, which underscores their value as myocardial imaging agents.

Zusammenfassung

Bei 20 Hunden wurde die Myokardspeicherung der radiojodierten Heptadekansäure (¹³¹IHDA) und Pentadekansäure (¹²⁵IPPA) im Vergleich mit ²⁰¹T1 bestimmt. Drei verschiedene Gruppen wurden untersucht: Gruppe A, 10 Hunde (6 mit Koronararterienverschluß) nach intravenöser Injektion von ¹³¹I-HDA und ²⁰¹T1; Gruppe B, 5 Hunde (mit Verschluß) nach Verabreichung von ¹²⁵I-PPA und ²⁰¹T1; Gruppe C, 5 Hunde (mit Verschluß) nach Verabreichung von ¹²⁵I-PPA und ¹³¹I-HDA. 2 Min. nach Verabreichung der Verbindungen wurden die Herzen entnommen und in Formaldehyd gelagert. Die Aktivitätsanreicherung in Schnitten des linken Ventrikels wurde in Prozent der verabreichten Dosis ausgedrückt. Die Speicherung im normalen Herz (Gruppe A) betrug 4,2 ±0,6% für ¹³¹I-HDA und ±0,7% für ²⁰¹T1. Die Speicherung im betroffenen Myokard (Gruppe A) betrug 2,6 ±0,4% für ¹³¹I-HDA (p<0,001) und 3,4 ±0,6% für ²⁰¹T1 (p<0,01). Die Aktivitätsanreicherung aller 3 Verbindungen in Gruppe B und C ergab keine signifikanten Unterschiede: Gruppe B, ¹²⁵I-PPA 2,8 ±0,8% und ²⁰¹T1 2,5 ±0,5%; Gruppe C, ¹²⁵I-PPA 1,9 ±0,7% und ¹³¹I-HDA 1,6 ±0,6%. Auch die regionale Verteilung der beiden Jodfettsäuren war entsprechend vergleichbar mit der Verteilung der ²⁰¹T1 Aktivität. Wir schließen daraus, daß radiojodierte Hepta-und Pentadekansäure, so wie ²⁰¹T1, gute Tracer für die Beurteilung der myokardialen Perfusion sind.

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