An understanding of the natural history of childhood chronic idiopathic thrombocytopenia purpura (ITP) could contribute to a rational therapeutic approach to its treatment, which remains controversial. In our retrospective study of 92 children with ITP, 22 had a chronic course and were followed for 3-14 years (median 8.6 years). Treatment, when indicated, was individualized: 4 patients (18.2%) did not receive any treatment, 14 (63.6%) received steroids only, while 4 (18.2%) were treated with steroids and one of the following: high-dose gamma globulin (4 patients), splenectomy (2 patients) or immunosuppressive therapy (2 patients). During follow-up, 14 patients (63.6%) achieved complete remission, 5 (22.7%) partial remission and only 3 (13.5%) remained severely thrombocytopenic, with minimal bleeding tendency. Eleven patients (50%) responded to the initial prednisone course (1-5 mg/kg/day), but showed a marked decrease in platelet count when steroids were tapered off. In view of the high rates of complete and partial remission and the mild course of the few non-responding patients, it is suggested that with adequate supportive therapy, follow-up problems and fatalities can be kept to a minimum. We believe that aggressive therapy, such as splenectomy, should be reserved for the rare symptomatic and severely thrombocytopenic patient.

KREC but not TREC levels are different in patients comparing to controls, pointing to an overreaction of B-cell development as a role in the pathogenesis of ITP. These results may shed more lights on the immune mechanism of ITP.

55 RENAL GRGWH. Wilton, P . , Larsson, L. Karolinska I n s t i t u t e , Stockholm, Sweden.Rats were nephrectomized (Nx) o r sham-operated (S) a t t h e age of 5, 12 and 40 days. One group of r a t s was Nx i n u t e r o 3-4 days before d e l i v e r y . Light microscopy s t u d i e s of r e n a l s t r u c t u r a l development were c a r r i e d o u t i n t h e p o s t n a t a l Nx and S r a t s a t t h e age of 6-26 days. Renal s t r u c t u r a l development followed t h e same p a t t e r n i n Nx a s i n S r a t s . The formation of new nephrons was completed a t t h e age of 6-7 days. There was no s t r u c t u r a l evidence of formation of new nephrons. Furthermore, glomerular counting showed t h e same number o f glomeruli i n Nx and S r a t s a t t h e age of 60 days. The number of glomeruli i n f e t a l nephrectomized r a t s was t h e same a s i n c o n t r o l animals from t h e same l i t t e r . GFR, SNGFR and kidney weight were estimated a t 60 days o f a g e i n Nx and S r a t s . The compensatory i n c r e a s e i n r e n a l weight and GFR was most pronounced i n r a t s Nx a t t h e age of 5 days, i . e . j u s t b e f o r e t h e formation of nephrons was completed.The q u o t i e n t between t h e recorded SNGFR and GFR was t h e same i n a l l groups s t u d i e d , i n d i c a t i n g a homogenous i n c r e a s e i n SNGFR of t h e nephrons a t a l l c o r t i c a l l e v e l s . AGE RELATED DIFFERENCES I N ANGIOTENSIN I1 (A-11)56 METABOLISM IN RAT TISSUES. B a i l i e , M.D., Wallace, K. 8.. and Oparil. S. Michigan S t a t e University, EastLansing, Michigan and University of Alabama, Birmingham, Alabama, USA.I n o r d e r t o attempt t o account f o r age-related d i f f e r e n c e s i n plasma a n g i o t e n s i n I1 concentration, t h e a c t i v i t y of angiotensina s e s i n developing r a t t i s s u e s was examined. The r a t e of degrad a t i o n of A-I1 was determined i n v i t r o during incubation of tiss u e homogenates w i t h 125-I-tyrosine labeled a n g i o t e n s i n 11. Pept i d e fragments were s e p a r a t e d e l e c t r o p h o r e t i c a l l y and q u a n t i f i e d by gamma s c i n t i l l a t i o n counting. H a l f -l i f e of labeled A-I1 i n plasma o r l i v e r homogenates d i d not change w i t h age. I n cont r a s t , t h e h a l f -l i f e i n r e n a l t i s s u e homogenates decreased from 8.4 + 1 . 2 minutes i n two-week-old r a t s t o 4.7 + 0.7 minutes i n eight-week-old r a t s and 2.8 + 1.8 minutes i n a d u l t s . This change i n t h e r a t e of disappearance was accompanied by concomitant inc r e a s e i n t h e r a t e of appearance of labeled p e p t i d e fragments. P e p t i d e mapping revealed t h a t t h e p r i n c i p a l m e t a b o l i t e of 125-A 1 1 was t y r o s i n e . The only o t h e r d e t e c t a b l e m e t a b o l i t e s of A-I1 were t h e amino-terminus t e t r a p e p t i d e and t h e carboxy-terminus hexapeptide. The appearance of t h e s e fragments w a s highly v n r ia b l e , suggesting t h a t endopepti...