A Comparison of the Measurement of Free Erythrocyte Porphyrin (Fep) and Red Cell Aminolevulinic Acid Dehydrase Activity (Alad) as Means of Determining Excessive Lead Absorption

Abstract

I n 700 s u b j e c t s , simultaneous measurements of FEP, ALAD and blood l e a d were performed. I n 92 s u b j e c t s , EDTA c h e l a t i o n t e s t s were c a r r i e d o u t i n a n attempt t o a s s e s s t h e s e n s i t i v i t y of t h e two screening procedures and t o determine how they r e f l e c t e d t h e c h e l a t a b l e body l e a d burden.Both t h e FEP and ALAD were abnormal i n a l l s u b j e c t s w i t h l e a d v a l u e s above 50 pgm%. The FEP was abnormal i n 86.4% of s u b j e c t s w i t h l e a d v a l u e s between 41-50 pgm%; t h e ALAD i n 81.3%. Of t h e s u b j e c t s surveyed, 9.3% had abnormal ALAD w h i l e 32.4%had abnormal FEP, r e f l e c t i n g t h e f a c t t h a t FEP is a l s o elevated i n i r o n deficiency. The mean u r i n a r y l e a d e x c r e t i o n w i t h FEP v a l u e s of l e s s than 100 was 0.25 pgm/mg EDTA admini s t e r e d and r o s e progressively with i n c r e a s i n g FEP; s u b j e c t s w i t h FEP v a l u e s a b w e 300 excreted 0.83 pgm/mg EDTA. The ALAD a l s o r e f l e c t e d t h e body l e a d burden. With ALAD v a l u e s above 25 u n i t s , l e a d e x c r e t i o n averaged 0.16 ugmlmg EDTA w h i l e w i t h ALAD v a l u e s of l e s s than 1 5 u n i t s t h e u r i n a r y e x c r e t i o n was 0.65 pgm/mg EDTA. Both t h e FEP and ALAD a r e s e n s i t i v e t e s t s of t h e body l e a d burden and c o r r e l a t e w i t h t h e EDTA m o b i l i z a t i o n t e s t . The s i m p l i c i t y of t h e FEP makes i t more u s e f u l d e s p i t e i t s p o s i t i v i t y w i t h i r o n deficiency. A 2 year old M and a 10 year old F with 21-day c y c l e s of neutropenia and apthous s t o m a t i t i s were s t u d i e d . Bone marrow a s p i r a t e s a t t h e c y c l e s ' n a d i r showed a maturation a rr e s t a t t h e myelocyte s t a g e . I n v i t r o bone marrow c u l t u r e i n agar documented q u a n t i t a t i v e l y normal colony formation w i t h r a r e c o l o n i e s of n e u t r o p h i l s (PMN). S e r i a l l i q u i d suspension c u l t u r e s (Marbrook chamber) yielded c e l l counts which were i n t h e normal range o r higher than companion cont r o l c u l t u r e s . CN PMN maturation was d e f e c t i v e e a r l y i n cult u r e ; some mature PMNs appeared a f t e r 7 days and p e r s i s t e d f o r up t o 25 days. Plasma, obtained from normal donors and from those given typhoid vaccine and plasmaphoresed 1 hour l a t e r , was assayed f o r CSA, using normal and CN bone marrow. Only plasma which stimulated normal marrow promoted PMN maturation i n CN marrow i n v i t r o . I n vivo, a d m i n i s t r a t i o n of plasma containing CSA increased PMN production and ameliorated t h e c l i n i c a l symptoms of neutropenia. I t i s concluded t h a t one type of CN involves a maturation d e f e c t of PMNs, which may be a l t e r e d i n v i t r o and i n vivo by plasma c o n t a i n i n g CSA. Supported by Grant 5-M01-RR00199. SERUM LUTEINIZING HORMONE (LH) AND FOLLICLE STIMULATING HOR-...